Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) 1. Check out textbook. Read and Note Chapters 1 and 2. Pay careful attention to significant figure rules and calculations. 2. Make quizlets/flashcards for element and polyatomic ion quizzes below. There is a periodic table on the back inside cover of your textbook and you can find the tables below on pgs. 219 and 221. 3. Read: Understanding Science. (below) 4. Read: How to study chemistry. (below) 5. Do experimental methods practice. (below) 6. Do making measurements, scientific notation, and significant figures practice. (below) ELEMENTS TO KNOW ‐ You will be able to use the Periodic Table provided by the ACT Chemistry Final I give you the symbol and you write the name or I give you the name and you write the symbol. QUIZ #1 — Friday September 4, 2015: atomic numbers 1‐20 QUIZ #2 — Friday September 11, 2015: 21‐40 QUIZ #3 — Friday September 18, 2015: 41, 42, 44‐58, 61, 63, 71 QUIZ #4 — Friday September 25, 2015: 74‐83, 85‐89, 92, 94‐96, 100 QUIZ #5 – OVER ALL 80 (38 out of the 80 will be on the quiz): Friday October 2, 2015 Quiz #6 – First 10 polyatomics ions Quiz #7 ‐‐ Next 10 polyatomic ions Quiz #8 ‐‐ Remaining 6 polyatomic ions and monoatomic transition metal ions. Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) HOW TO STUDY CHEMISTRY EFFECTIVELY
Introduction
Every student would like an A in chemistry. Many students, however, first need to learn the techniques that will
help them earn high grades. If you have been successful in the past without ever thinking about how to study,
you might not be prepared for the fact that chemistry courses require a great deal of independent learning, and
that you have to integrate material from lecture, textbooks, handouts, labs, and problems. The techniques
described here will help you study chemistry and other sciences more effectively, They will not only improve
your grades but will give you more confidence as well, so that learning chemistry is a pleasure rather than a
chore.
How to Read and Understand Your Textbook
Many students make the mistake of reading a textbook like a novel; they read and entire chapter once and then
attempts to do the problems. It's not surprising that the problems appear too difficult and seem to belong to
some other chapter. To learn the most from a textbook, you must actively read; that is, you must constantly be
thinking about what you are reading, pausing to relate it to what you have just read before, and making sure you
understand its applications. Ask yourself questions to make sure you are understanding the main ideas of the
paragraphs; turn section headings into questions and then relate sections to each other and to the main topic of
the reading assignment. Asking and answering questions helps you to not only concentrate on the main ideas
but also increases your retention of the material. Your textbook provides you with learning objectives for each
section; use those objectives to focus your attention on what you need to know. The process of self-testing is a
skill that scientists at all levels use to learn new concepts. For the student, it is particularly helpful since it is
also a form of exam preparation; answering questions on exams will be less anxiety producing when you have
been answering questions all along.
To help yourself read actively, take notes in outline form on the text material. Your outline should include main
ideas, important formulas, and their applications. I have included a note taking format at the end of this
document that can help guide you to include everything you need.
Survey chapters before you begin to actively read. That is, note the main headings and subheadings, read the
introduction (previews in your text) to see how this chapter relates to previous chapters, read the lists of
learning objectives, turn to the key terms and important formulas at the end of the chapter; these will all direct
your attention to what you must learn from the text. Read each paragraph first, and then go back and outline
only the important material. Review your notes after you finish, briefly going over main ideas and examples.
Make an effort to understand and retain the material by engaging as many senses as possible as you actively
read. Try to visualize many of the principles and examples described in the text. Remember chemistry describes
the world in which you live, so that much of what you learn you can apply to familiar objects and situations.
Make sure you spend a significant portion of your study time doing problems. Your textbook provides you with
many clearly worked-out examples followed by practice exercises. The only way you can be sure you really
understand the problems is by doing them yourself. Even if you follow the solutions in your text, this is no
guarantee that you understand the problem well enough to do one like it on your own. By doing the practice
exercises (HOMEWORK), you will not only ensure that you really understand the examples, but you will
increase your chances of solving similar problems on an exam. People that play a musical instrument spend a
lot more time practicing than actually performing. In any sport, players spend much more time in practice than
in playing the game. In order to get good at anything you must practice!!! After completing a section, try to do
the exercises assigned to you for that section. Keep in mind that chemistry is a problem-solving discipline, so
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) that the more problems you solve, the better you will understand the material. As you read, make a note of other
parts of the text that are not clear to you and also of the examples and exercises you are not sure of or can't do at
all. Consult 1) lecture notes, 2) study guide, 3) instructors, and 4) classmates to clear up what you don't
understand. Never let your questions go unanswered; if you do, you not only decrease your chances of doing
well on exams, but you jeopardize your future understanding of chemistry since new topics very often depend
on your understanding of past topics.
1. Survey the chapter.
2. Outline or underline as you read actively.
3. Do practice exercises and final exercises.
4. Keep a record of questions and any problems you don't completely understand, so that you can consult
instructors, classmates, textbooks, or lecture notes for answers.
Getting the Most Out of the Lecture
In listening as in reading, you must be actively involved to get the most out of it. If you actively listen to the
lecture, your notes will be accurate and complete, and your time in the lecture room will be well spent.
Read and take notes on the assigned material before you come to lecture. If you don't, much of your lecture time
will be wasted. Without some idea of the topic being discussed, you will find it difficult to focus on the
important ideas of the lecture. Your notes will be incomplete, and you won't be able to ask questions; the lecture
will not help you to learn the material. On the other hand, if you arrive prepared, you will be able to determine
and record the important information so that your notes will be useful for studying and for exam preparation.
Bring your own notes to class and add any needed details. Pay close attention to the examples that were worked
out in class and try to re-do them after class, perhaps even changing values for practice.
Read over you notes as soon as possible, preferably the same day. Rewrite what is unclear. If you are uncertain
about parts of what was said, compare your notes with those of other students, check the PowerPoint lectures on
Canvas, or ask your instructor. Then go back and include that material in you notes. Think of your notes as a
handwritten book and strive to make the accurate and complete.
1. Read the assignment before the lecture.
2. Try to take notes in outline form showing major topics, and their relationships. Include examples.
3. Read over notes the same day. Re-write, change, and add to notes where necessary.
4. Make sure your notes are complete. If you missed part of the lecture, find out what it was you omitted and fill
it in.
Solving Problems
Most of your time in chemistry should be spent solving problems that are applications of concepts and formulas
learned in lecture and from the text. You can improve you ability to solve problems by learning how to think
about the examples that are solved for you in the text, study guide, and in the lecture, and also by learning how
to think about the many relationships (formulas) used in the problem.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Understanding relationships and formulas is crucial to learning chemistry. Many students memorize
relationships and formulas without taking the time and energy to think about them. This often leads to
inappropriate applications and incorrectly solved problems. Ask yourself the following questions whenever you
learn a new formula.
1. What system or change does this formula describe? What do the variables mean and what are their units?
2. When does it apply?
3. What are some examples of its application? What is its significance?
Formulas are listed for you in each chapter. Ask yourself these questions for all of these relationships. Make a
set of "Important Formula" charts. If you actually think about relationships as you learn them, it will be easier to
see how to apply them.
Note carefully which concept or relationships are used in the worked-out problems in the text, study guide, and
solutions manual. Why was this formula used and not one of the others in the chapter? What information given
in the problem indicates that the problem should be solved in this way? You will find answers to these kinds of
questions in the "Problem-Solving Tips" given in the study guide.
When you start to work on a problem, it is critical to first write down the information that is given (along with
units) and to identify the unknown. Use a diagram whenever possible to show what is being described in the
problem, and indicate the given and unknown values. Then try to plan out your solution before you start doing
and calculations. If you aimlessly calculate values, you may generate superfluous data that may be confusing.
To solve a problem, you must determine which relationships are relevant out of all those you have learned.
Think of relationships that involve your unknown. Which ones include all or some of the given data? Be sure
the relationships you use apply to the system as described in the problem; for example don't use formulas for
gases in a problem about liquids. If you still can't see a method, think about relationships that involved the other
values given in the problem. For example, if the volume and density of a solution are provided, then the mass is
also known (d= m/V). If you now include the mass with known information, the solution may become apparent.
Think about the example problems you have studied. Solutions to previous problems may provide hints to
solving new problems.
After you have planned the solution, then do the calculations. Use a calculator to save time and eliminate
arithmetic errors. Be sure that the values you use have the appropriate units for the formula you are applying.
Check your answers for the following:
1. Make sure your answer is what the problem asked for.
2. Make sure your answer is reasonable. When you study example problems in your text and study guide, think
about the magnitudes of the answers so that you will have some concept of reasonable answers. If you calculate
that the mass of a molecule is 10kg, it is clear that you have made an error. However, if you calculate that 10^6
kJ/mol of heat are released by a reaction, you will not realize that you have made and error unless you have
previously noted reasonable values for heat being released from chemical reactions.
3. Make sure your answer has the correct number of significant figures.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Problem-Solving Tips:
1. Identify the known quantities and the unknown quantities asked for.
2. Plan the solution: What do you know about the unknown that might link it to given information?
3. Perform calculations.
4. Check your answers.
Managing Your Time
Learn to manage your time. This skill will be invaluable, especially if you plan a career in science. Learning
chemistry takes time and energy, and you should try to study some chemistry nearly every day. Devise a study
schedule at the beginning of each week so that you will be studying chemistry throughout the week. Include
periods for textbook reading before lecture, review of lecture notes, problem solving, and review for quizzes
and exams. Make sure that your study schedule not only includes enough time to study chemistry, but also
allocates sufficient time for other activities that you must complete during the course of the week.
Be specific in constructing your schedule; indicate which chapters or sections you plan to study, which set of
problems to work out, and which topics to review for an approaching exam. Try not to schedule very long
blocks of time for studying chemistry: 1- or 2-hour blocks of time interspersed with other work for different
courses are best.
Devise your schedule at the beginning of each week by first looking at all of your assignments and then
allowing enough time to complete them. Students tend to complete their assignments more often when they
schedule chapter readings and problem solving at the beginning of the week and reviewing towards the end.
Always allow yourself more time than you think you will actually need to complete the assignment. It is always
better to overestimate the time you will need than to find out that you are short of time later.
It is critical that you follow your schedule and don't permit yourself to be distracted. If you carefully construct
and follow your schedule and make necessary adjustments to accommodate each week's requirements, you
should find that your free time may actually increase.
1. Construct a study schedule at the beginning of each week.
2. Be specific as to what you plan to do during your study sessions.
3. Over estimate the time you will need to complete each assignment.
4. Be sure to include in your schedule enough time to complete all other necessary tasks as well as time for
leisure activities.
Tips on Creating a Study Area
To help you concentration, create a study space. Study in an area where lighting is adequate and distractions are
few. Try to create an environment that is pleasant but without items that might divert your attention such as a
radio, stereo, television, or telephone. Make sure that everything that you might need for studying is in your
study area. This should include: paper, pens and pencils, calculator, computer, notes, outlines, and completed
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) assignments as well as all textbooks and reference books that might be needed. Try to use your study area solely
for the purpose of studying.
By creating a study space, you make your studying more efficient. You will reduce wasted time searching for
needed material and minimize distractions, thus improving your concentration.
1. Study in a comfortable but efficient area minimizing distractions.
2. Make sure that your study area is equipped with all the items you will need for studying.
Using Study Groups
The effective use of study groups can be an important part of an overall study program that will lead to success
in General Chemistry. However, many students have tried to use study groups, only to find that they were not
helpful. Generally, study groups fail when students either do not know how to form an effective group or do not
know what tasks a study group is best suited to perform.
Study groups should consist of three to six members who are serious chemistry students and committed to
making the group meetings effective. It's generally a good idea to establish a consistent study time and place: 2
hours at the end of the week (with more frequent meetings as an examination approaches) at your college (a
study area of a dormitory usually suffices). Study groups are most effective for reviewing material that each
student has previously studied on their own such as assigned chapters, problems, and old exams. If members do
not individually prepare, the group meetings will not be helpful.
Each participant should be assigned a specific task to complete and present to the group. These tasks include
solving specific problems, explaining sections of a chapter or of a lecture, preparing a chapter outline, etc. Each
member should be responsible for covering different aspects of the material; the group will be assured of
covering all the assignments. In addition, each member is accountable to the group as a whole, which has the
effect of encouraging students to keep up with the course work.
Study groups acquire particular significance when preparing for a chemistry exam. While they are not a
substitute for the review that should normally take place before an exam, they can be an important addition to
that review process. Usually, it is a good idea to increase the amount of time a study group meets about 2 weeks
prior to a major chemistry exam (usually from 2 to 4 hours a week). The additional time should be used for a
general review of the material and for problem solving. Remember chemistry exams usually emphasize problem
solving so that the group should spend most of its preparation seeking and understanding solutions to problems.
Each member of the study group should prepare and explain to the group a section of the material that is to be
covered on the exam and also to develop a set of problems and answers that encompasses the same material.
Problems should be distributed to the rest of the group without the answers, and difficulty with certain problems
can rely on the member of the group who developed the problem to explain the answer. This kind of studying
for exams is extremely effective because it puts you, the student, in the role of the professor, deciding what
information is important and likely to be covered on an exam and what is not. The process is also effective
because it requires you to be actively involved in the learning of formulas and reviewing and what material you
already know sufficiently.
1. Form a study group consisting of three to six serious chemistry students.
2. Try to convene at the same place and same time weekly.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) 3. Assign specific tasks to members.
4. Spend most of your time discussing and solving problems.
5. Increase the time for your sessions to prepare for exams. Each member should be responsible for preparing
and presenting material that will appear on the upcoming test.
In addition to study groups Bexley offers peer tutoring. Ask your teacher if you would like more information.
Preparing for and Taking Exams
To adequately prepare for an exam, you must first organize your time in advance. Start studying a few weeks
before an exam by adding time to your usual study schedule, and use this additional time for exam preparation
only. Survey the material that will be covered on the exam, and divide the relevant topics or chapters into
categories based on your present level of understanding. For example, identify chapters that you know well,
those that you have a limited mastery of, and finally topics that you do not understand at all. Write out an
approximate but detailed schedule including not only main chapters or topics you plan to cover during each
week, but also specifically what you plan to study each day. Leave more time for the material you are unsure of
as well as for the more lengthy and complex topics, and spend most of your time solving problems. Because
chemistry exams generally consist mostly of problem solving, your preparation can only be effective if you
actually solve many relevant problems. Review the assigned problems, and solve additional problems in the text
and study guide as well as from previous exams, if available.
Be careful not to review only the solutions of problems. Students who just review the solutions often find that
they cannot solve problems on exams. The only way that you can be sure that you adequately understand any
problem is by solving it yourself, writing out each step. For problems already solved, simply change given
values and rework the problem finding a different answer. Remember, to be successful on a problem-solving
exam, you must have the experience of solving many problems yourself.
Review you old exams to refamiliarize yourself with the kinds of questions you professor asks. Identify the
questions you were most successful answering as well as those you could not correctly complete. Try to
emphasize problems that resemble those that were particularly difficult for you in the past.
Try to work in a study group where you can solve problems and review lecture and textbook notes together.
You will find it helpful to construct outlines of the work being covered; each member of your group can
contribute outlines of specific topics as well as present solutions to the relevant problems. Remember, the more
you write and think about the topics, the more you will retain and understand. Study group members can also
develop new problems that the entire group can work on under simulated exam conditions. Such exercises will
help to reveal your weak areas and develop test-taking skills.
1. Devise a schedule for preparation a few weeks before the exam.
2. Determine which topics you know well, which topics you do not understand completely, and what material
you do not know at all.
3. Spend most of your time actually solving assigned problems, as well as new problems from your text, study
guide, and previous exams.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) 4. Review previous exams to remind yourself of how your knowledge will be tested.
5. Work with your study group as much as possible developing outlines, solving problems, and creating practice
exams.
The Night Before the Exam.
The night before the exam should be used for a quick review of the more important topics or a review of the
material you are still uncertain about. At this point, you should have studied all of the relevant topics and
associated problems. Chemistry cannot be learned overnight and any attempts at cramming the work will only
result in more anxiety during the exam. Learning any science is a gradual process requiring much time and
energy. Remember that your exam grades will reflect your study techniques. Adequate preparation not only
increases your knowledge and improves the skills required for the exam, but also reduces your anxiety level so
that you can think more clearly.
Taking the Exam.
Read the directions carefully, and work first on the problems or questions you think you can answer correctly.
Leave the problems you are very uncertain about for last. In this way, you will ensure that you receive credit for
what you know and also you will elevate you confidence level to help you tackle those problems that you find
challenging.
Try to show clearly each step you take in solving a problem so that you can check your work more efficiently
and also so that your instructor can assign partial credit if that is his or her policy. After you solve a problem,
make sure that you calculated the required quantity and that your value is reasonable. Make sure your calculator
can perform all required operations, and replace your batteries before the exam.
1. Read instructions carefully.
2. Answer the questions or solve the problems you feel sure about.
3. Show all work clearly.
4. Use a calculator with all required functions.
5. Check your answers to see if they match the questions and if they are reasonable.
The Laboratory Period
Many chemistry courses have laboratory components. Students often do not consider the laboratory exercises
important and consequently do not benefit from the experiments. However, laboratory exercises usually
emphasize important concepts and also introduce laboratory skills that will be needed for more advanced
courses. If you appropriately prepare, perform, and write up the laboratory experiments, you will benefit in the
following ways:
1. You will develop a solid understanding of the concepts emphasized in the laboratory.
2. You will earn high grades for the lab component of your course.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) 3. You will learn lab techniques that you will need in future science courses and in scientific research.
4. You will acquire an understanding of scientific methods, which is necessary in order to understand scientific
journal articles and to conduct research.
Be sure to take notes during the prelab while the teacher demonstrates proper use of equipment and techniques
and read procedures if they are given to you in advance.
READING GUIDE
Chapter & Section: _______________________________________
MAJOR TOPICS (read the headings):
KEY WORDS AND THEIR MEANING:
SUMMARY (remember, write 0 - 2 sentences for each paragraph):
SAMPLE QUESTIONS & ANSWERS:
(no credit for “wimpy” questions)
More specific strategies: 
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Chemistry exams require more than memorization. You will have to change many of your study strategies. Get help early. Do not wait until the day before a test to finally ask. Get free tutoring from peer tutors! Attend all classes and labs. Always complete the homework. Plan to read, review, and study each day rather than the night before a quiz or exam. Unlike some other courses where cramming works, chemistry requires daily attention. Remember reading 10 pages in chemistry is not the same as reading 10 pages in humanities. Scientific text is very dense because it contains formulas, graphs, illustrations, and difficult abstract concepts. You will need to allot more time to read and think about your assignments. It may take you 50 minutes to master 5 pages in a chemistry textbook. Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) 
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To improve concentration break up your assignments into smaller tasks. 5 pages per sitting versus 20 pages is much easier to stay focused. Read actively and think about ideas. Delve into your own metacognition. Do you understand what you are reading or are you just reading the words? Take notes using some strategy that you have learned and liked. Cornell, the above method, 3QSR, etc. Be sure to include summaries on the illustrations and formulas in your book. Those tables, graphs, and pictures are supporting your understanding of the ideas in the paragraph. As you read and study, identify what you do know, and what you don’t know. Review the learning objectives. Can you find the material that you studied for the objective? Keep a list of questions so you can sek help from your study group, your tutor, or your teacher. Look for podcasts or videos to watch on that topic. There is a lot of information out there to support you. You do not want to wait until the night before an exam to find out you cannot solve a certain problem. Take the time to review the lecture notes on Canvas and the end of section and chapter reviews. Make sure your own notes includes the information. Be sure to take the time to review any notes you took in class and rewrite them. If you discover concepts or ideas that make no sense to you seek help immediately. Read in your book, search for a video, ask your study group, ask a tutor, or ask your teacher. Remember, much of your learning now is independent. Don’t wait until the next day to try to figure it out. To prepare for an exam, take the time to solve a significant number of problems and review questions. As you work a problem or question make sure you are able to answer the following question for each: What kind of problem is this. Why. What is the underlying concept being asked about? Find a study partner. Meet with that person on a weekly basis to explain concepts to each other. Choose someone who is a serious student. Many former students have told me that they learned a lot explaining it out loud to another person. Practice problem solving out loud. Imagine you are teaching someone the chemistry concepts. Very powerful way to place the concepts into long term memory. After each exam, take the time to review and correct it. Look for the following: a) Did I miss any questions because I misread the item or choices? b) Did I miss any questions because I did not fully read and consider all the choices? c) Did I miss any questions because I just did not know the concept? Do I need to study my notes more, the textbook, other? Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Experimental Methods Practice: In the scenarios below (1 -3), identify the following components of an experiment.
1. Independent variable
2. Dependent variable
3. Control
4. Repeated trials
5. Constants
Use the scenarios below (1-3) to write a title and a hypothesis using the following formats:
6. Title: The Effect of the (changes in the independent variable) on the (dependent variable)
7. Hypothesis: If the (independent variable – describe how it will be changed), then the
(dependent variable – describe the effect).
Scenario 1 Floor Wax
A shopping mall wanted to determine whether the more expensive “Tough Stuff” floor wax was
better then the cheaper “Steel Seal” floor wax at protecting its floor tiles against scratches. One liter
of each brand of floor wax was applied to each of 5 test sections of the main hall of the mall. The
test sections were all the same size and were covered with the same kind of tiles. Five (5) other test
sections received no wax. After 3 weeks, the number of scratches in each of the test sections was
counted.
Scenario 2 Brands of Car Wax
Jack wanted to test which brand of car wax was most effective. He tested four brands of wax. He
cleaned the hood of his car and removed the old wax. He measured four equal sections on the
hood of the car. Each of the waxes was used to cover a section. An equal amount of wax, the
same type of rag, and equal buffing were used. Five drops of water were placed on each square,
and the diameter of each drop was measured (cm) (quantitative). Jack could have used a qualitative
dependent variable by developing a rating scale for amount of shine, from dull to very shiny.
Scenario 3 Compost and Bean Plants
After learning about recycling, members of John’s biology class investigated the effect of various
recycled products on plant growth. John’s lab group compared the effect of different-aged grass
compost on bean plants. Because composition is necessary for release of nutrients, the group
hypothesized that older grass compost would produce taller bean plants. Three flats of bean plants
(25 plants/flat) were grown for 5 days. The plants were then fertilized as follows: (a) Flat A: 450 g
of 3-month-old compost, (b) Flat B: 450 g of 6 month-old compost, and (c) Flat C: 0 g compost.
The plants received the same amount of sunlight and water each day. At the end of 30 days the
group recorded the height of the plants (cm).
Can you find what is wrong with these Scientific Method Experiments?
Scenario 4 Metals and Rusting Iron
In chemistry class, Allen determined the effectiveness of various metals in releasing hydrogen gas
from hydrochloric acid. Several weeks later, Allen read that a utilities company was burying lead
next to iron pipes to prevent rusting. Allen hypothesized that less rusting would occur with the
more active metals. He placed the following into 4 separate beakers of water: (a) 1 iron nail, (b) 1
iron nail wrapped with an aluminum strip, (c) 1 iron nail wrapped with a magnesium strip, and (d)
1 iron nail wrapped with a lead strip. He used the same amount of water, equal amounts (mass) of
the metals, and the same type of iron nails. At the end of 5 days, he rated the amount of rusting as
small, moderate, or large. He also recorded the color of the water.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Scenario 5 Perfumes and Bees’ Behavior
JoAnna red that certain perfume esters would agitate bees. Because perfume formulas are secret,
she decided to determine whether the unknown Ester X was present in four different perfumes by
observing the bee’s behavior. She placed a saucer containing 10 mL of the first perfume 3 m from
the hive. She recorded the time required for the bees to emerge and made observations on their
behavior. After a 30-minute recovery period, she tested the second, third, and fourth perfumes. All
experiments were conduced on the same day when the weather conditions were similar; that is, air
temperature and wind.
Scenario 6 Fossils and Cliff Depth
Susan observed that different kinds and amounts of fossils were present in a cliff behind her house.
She wondered if changes in fossil content occurred from the top to the bottom of the bank. She
marked the bank at five positions: 5, 10, 15, 20, 25 m from the surface. She removed 1 bucket of
soil from each of the positions and determined the kind and number of fossils in each sample.
Scenario 7 Aloe vera and Planaria
Jackie read that Aloe vera promoted healing on burned tissue. She decided to investigate the effect
of various amounts of Aloe vera on the regeneration of planaria. She bisected the planaria to obtain
10 parts (5 heads and 5 tails) for each experimental group. She applied concentrations of 0%, 10%,
20%, and 30% Aloe vera to the groups. Fifteen mL of Aloe vera solutions were applied. All planaria
were maintained in a growth chamber with identical food, temperature, and humidity. On day 15,
Jackie observed the regeneration of the planaria parts and categorized development as full, partial, or
none.
For each of the scenarios below answer questions A-D.
A. Identify the independent variable, levels of the independent variable, dependant
variable, number of repeated trials, constants, and control (if present).
B. Identify the hypothesis for the experiment. If the hypothesis is not explicitly stated,
write one for the scenario.
C. Draw an experimental design diagram, which includes an appropriate title and
hypothesis.
D. State at least two ways to improve the experiment described in the scenario.
1. Ten seeds were planted each in 5 pots found around the house that contained 500 g of
“Peter’s Potting Soil.” The pots were given the following amounts of distilled water each day
for 40 days.
Pot 1, 50 mL; Pot 2, 100 mL; Pot 3, 150 mL; Pot 4, 200 mL; Pot 5, 250 mL.
Because Pot 3 received the recommended amount of water, it was used as a control. The height
of each plant was measured at the end of the experiment.
2. Gloria wanted to find out if the color of food would affect whether kindergarten children
would select it for lunch. She put food coloring into 5 identical bowls of mashed potatoes. The
colors were plain, red, green, yellow, and blue. Each child chose a scoop of potatoes of the
color of their choice. Gloria did this experiment using 100 students. She recorded the number
of students that chose each color.
3. Susie wondered if the height of a hole punched in the side of a quartz-size milk carton would
affect how far from the container a liquid would spurt when the carton was full of the liquid.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) She used 4 identical cartons and punched the same size hole in each. The hole was placed at a
different height on one side of each of the containers. The height of the holes varied in
increments of 5 cm, ranging from 5 cm to 20 cm from the base of the carton. She put her finger
over the holes and filled the cartons to a height of 25 cm with a liquid. When each carton was
filled to the proper level, she placed it in the sink and removed her finger. Susie measured how
far away from the carton’s base the liquid had squirted when it hit the bottom of the sink.
4. Sandy heard that plants compete for space. She decided to test this idea. She bought a
mixture of flower seeds and some potting soil. Into each of 5 plastic cups she put the same
amount of soil. In the first cup she planted 2 seeds, in the second cup she planted 4 seeds, in
the third cup 8 seeds, and in the fourth cup she planted 16 seeds. In the last cup she planted 32
seeds. After 25 days, she determined which set of plants looked best.
5. Esther became interested in insulation while her parent’s new house was being built. She
decided to determine which insulation transferred the least heat. She filled each of 5 jars halffull
with water. She sealed each jar with a plastic lid. Then she wrapped each jar with a different
kind of insulation. She put the jars outside in the direct sunlight. Later, she measured the
temperature of the water in each jar. Making Measurements in science: At the most basic level, chemistry (indeed all of science) depends upon experimentation; experimentation in
turn requires numerical measurements. And measurements are always taken from instruments made by other
human beings.
Some information about measurements:
1) Examples we will study include the metric ruler, the thermometer, and the graduated cylinder. Note: we will
use pan balances a lot in class. Make sure you write down every digit even if it is a zero. The volumetric flask is
the most precise way to measure a volume of liquid, but most of the time we will use a graduated cylinder.
Never use a beaker to measure precise volumes of liquids, only use them to transfer liquids, hold liquids that are
not a part of the experiment, or when precision is not required.
2) Because of the involvement of human beings, NO measurement is exact; some error is always involved. This
means that every answer in science has some uncertainty associated with it. We might be fairly confident we
have the correct answer, but we can never be 100% certain we have the EXACT correct answer.
3) Measurements always have two parts - a numerical part (sometimes called a factor) and a dimension
(sometimes called a label or a unit). The reason for this is that we are measuring quantities - length, elapsed
time, temperature, mass, etc. Not only do we have to tell how much there is, but we have to tell how much of
what.
In a mathematics class, units are inconsistently used. This is because much of mathematics discusses the
relationships between pure numbers, not the use of a number which describes an amount of something. Many
chemistry students have the unfortunate tendency to see units are unnecessary. THEY ARE NOT. You must
include them with every measurement and calculation with measurements that you make.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Measuring gives significance (or meaning) to each digit in the number produced. This concept of significance,
of what is and what is not significant is VERY IMPORTANT. Especially the "what is not" portion. Pay close
attention to the examples presented. The concept of significant figures (or significant digits) is important and
will play a role in almost every unit studied.
A measurement can be defined as the comparison of the dimensions of an object to some standard.
The dimensions of an object refer to some property the object possesses. Examples include mass, length, area,
density, and electrical charge. Dimensions are often called units.
For example, the meter is the standard unit of length in science. It was first defined as one ten-millionth of the
distance from the equator to the pole. Then, a standard meter was made out of a platinum-iridium alloy and kept
in a carefully controlled environment in Paris. The third definition was the distance of a certain number of wave
crests of a certain wavelength in the emission spectrum of krypton. The most recent definition of the meter is
the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second.
We will just use a ruler, thank you very much!
The metric ruler will be the first example of a measuring device. The whole numbers in the images represent
centimeters. The divisions are tenths of a centimeter, otherwise called millimeters. An arrow will represent the
end of an object being measured. Zero is always to the left.
Example #1:
1) We know for sure the object is more than 2 cm, but less than 3 cm.
2) We know for sure the object is more than 0.8 cm, but less than 0.9 cm.
How do we know these two things?
Look where the arrow is, it is to the right of 2, but short of 3. It is to the right of 0.8, but short of 0.9. So, I can
say the object is more than 2.8 cm, but less than 2.9 cm. We can say this with complete confidence because of
the markings on the ruler.
Can I say anything more about the length?
1) Look at the gap between the 0.8 and 0.9 cm, where the arrow is and, mentally, divide that gap into 10 equal
divisions.
2) Estimate how many tenths to the right the arrow is from the 0.8 cm.
Let us say your answer is two-tenths. We then say the object's length as 2.82 cm. The first two digits are 100%
certain, but the last, since it was estimated, has some error in it. But all three digits are significant.
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) This issue of estimation is important. Experience tells us that the human mind is capable of dividing a short
distance into tenths with acceptable reliability. However, there is error built in and it cannot be escaped. Since
the reliability is acceptable, we say the digit is significant, even with the built-in error.
However, the process stops there. ONLY ONE estimated digit is allowed to be significant. Simply put, every
line on a measurement device represents a certain digit. The measurer is expected to include all digits and then
estimate one more that does not have a line.
Make sure to always include the unit with the number.
Example #2:
What length is indicated by the arrow?
1) More than 4 cm, but less than 5 cm.
2) More than 0.5 cm, but less than 0.6 cm.
Correct answer = 4.50 cm. The arrow is pointing directly at the mark and is neither to the left nor to the right of
it.
Notice that whatever the smallest division in your scale is, you can always estimate to the next decimal place
after. In this case, the smallest division is in the tenth place, so we can estimate to the 0.01 place.
Be aware that there is some error, some uncertainty in the last digit of 4.50. While one should make an effort to
estimate as carefully as possible, there is still some room for error.
The rule about uncertain digits is that there can be one and only one estimated or uncertain digit in a
measurement. It is always the last digit in the measurement.
Here are two more examples of centimeter rulers. Decide what length is being shown.
Example #3:
Example #4:
Answer: 9.40 cm
Answer: 12.33 cm
Celsius thermometers used in high school typically have a scale with only whole numbers marked on the scale.
The gap between each whole number does not have any register marks for tenths. If you are using a digital
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) thermometer, write every digit even if it is a zero. They are all significant and the thermometer estimates the last
one for you.
Example #1:
Answer = 15.0 °C. Since the line stops exactly on the 15 line and DOES NOT go any farther, we
estimate that it has gone zero-tenths of the way from 15 to 16. We are allowed to include the tenth
degree value and have it be considered significant. Remember that when you use thermometers in
chemistry experiments. Many chemistry students have left off the `point zero' and get deducted for it.
Example #2:
The indicated temperature is 28.5 °C.
Remember to mentally divide up the gap between 28 and 29, then make your best estimate of how many
tenths are covered by the mark.
My best estimate was 0.5, but yours might have been a bit different. 0.4 and 0.6 are both acceptable.
You might be interested to learn that sometimes magnifying glasses are used to make the scale bigger.
This aids in the estimation process.
Here are two more examples of Celsius thermometers. Example #3 is to the left and example #4
is to the right. Decide what temperature is being shown.
Answer: 21.8 °C
°C
Answer: 36.0 Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) The graduated cylinder is another common component found in the chemistry laboratory. When reading
cylinders made of glass, the water forms a meniscus. This is the downward-curved surface of the water.
(Mercury forms an upward-curved meniscus.) Readings should always be made to the bottom point of the
meniscus.
What are the volumes indicated by these two graduated cylinders, first the left one (example #1) and then the
right one (example #2)? Keep in mind that you are allowed to estimate ONE decimal place PAST the smallest
scale division.
The left graduate (example #1) indicates a volume of 30.0 mL, since you can estimate one digit BEYOND the
smallest division. The smallest division is in the one's place, so that means you can estimate the tenth's place.
The right graduate (example #2) indicates a volume of 4.28 mL. The smallest division is the tenth place, so we
are allowed to estimate to the hundredth place. Here are two other graduated cylinder examples:
Answer: 27.5 mL
Answer: 5.00 mL
You can find more on the Chem Team website if you need additional practice. There are many tutorials there
for chemistry and you might want to bookmark the site for future reference.
http://www.chemteam.info/ChemTeamIndex.html
Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Honors Chemistry Summer Reading and Review (Optional, but strongly recommended by prior honors students) Define, compare, and contrast the following: models, hypotheses, predictions, inferences, theories, and laws. Read and Note Understanding Science First. (next) 1
What is science?
The word “science” probably brings to mind many different pictures: a fat textbook,
white lab coats and microscopes, an astronomer peering through a telescope, a naturalist in the rainforest, Einstein’s equations scribbled on a chalkboard, the launch of
the space shuttle, bubbling beakers …. All of those images reflect some aspect of science, but none of them provides a full picture because science has so many facets:
These images all show an aspect of science, but a complete view of science is more than any particular
instance.
• Science is both a body of knowledge and a process. In school, science may
sometimes seem like a collection of isolated and static facts listed in a textbook,
but that’s only a small part of the story. Just as importantly, science is also a process of discovery that allows us to link isolated facts into coherent and comprehensive understandings of the natural world.
• Science is exciting. Science is a way of discovering what’s in the universe and
how those things work today, how they worked in the past, and how they are likely to work in the future. Scientists are motivated by the thrill of seeing or figuring
out something that no one has before.
• Science is useful. The knowledge generated by science is powerful and reliable.
It can be used to develop new technologies, treat diseases, and deal with many
other sorts of problems.
• Science is ongoing. Science is continually refining and expanding our knowledge
of the universe, and as it does, it leads to new questions for future investigation.
Science will never be “finished.”
• Science is a global human endeavor. People all over the world participate in
the process of science. And you can too!
Diver photo provided by OAR/National Undersea Research Program (NURP); lab photo courtesy of Pacific Northwest National
Laboratory; photo of geologists on volcano by J.D. Griggs; photo of scientist in corn field by Scott Bauer; image of Mars
rover courtesy NASA/JPL-Caltech.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Discovery: The spark for science
“Eureka!” or “aha!” moments
may not happen frequently, but
they are often experiences that
drive science and scientists. For
a scientist, every day holds the
possibility of discovery—of coming up with a brand new idea or
of observing something that no
one has ever seen before. Vast
bodies of knowledge have yet to be built and many of the most basic questions about
the universe have yet to be answered:
• What causes gravity?
• How do tectonic plates move around on Earth’s surface?
• How do our brains store memories?
• How do water molecules interact with each other?
We don’t know the complete answers to these and an overwhelming number of other
questions, but the prospect of answering them beckons science forward.
EVERYDAY SCIENCE QUESTIONS
Scientific questions can seem complex
(e.g., what chemical reactions allow cells
to break the bonds in sugar molecules),
but they don’t have to be. You’ve probably posed many perfectly valid scientific
questions yourself: how can airplanes fly,
why do cakes rise in the oven, why do apples turn brown once they’re cut? You can
discover the answers to many of these
“everyday” science questions in your local library, but for others, science may not
have the answers yet, and answering such questions can lead to astonishing new
discoveries. For example, we still don’t know much about how your brain remembers to buy milk at the grocery store. Just as we’re motivated to answer questions about our everyday experiences, scientists confront such questions at all
scales, including questions about the very nature of the universe.
Discoveries, new questions, and new ideas are what keep scientists going and
awake at night, but they are only one part of the picture; the rest involves a lot
of hard (and sometimes tedious) work. In science, discoveries and ideas must be
verified by multiple lines of evidence and then integrated into the rest of science,
a process which can take many years. And often, discoveries are not bolts from
the blue. A discovery may itself be the result of many years of work on a particular problem, as illustrated by Henrietta Leavitt’s stellar discovery …
Photo of Spiral Galaxy M81 provided by NASA, ESA, and The Hubble Heritage Team (STScI/AURA); photo of water provided
by Andrew Davidhazy.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
3
STELLAR SURPRISES
Astronomers had long known about the existence of variable
stars—stars whose brightness changes over time, slowly
shifting between brilliant and dim—when, in 1912, Henrietta
Leavitt announced a remarkable (and totally unanticipated)
discovery about them. For these stars, the length of time
between their brightest and dimmest points seemed to be
related to their overall brightness: slower cycling stars are
more luminous. At the time, no one knew why that was the
case, but nevertheless, the discovery allowed astronomers
Henrietta Leavitt
to infer the distances to far-off stars, and hence, to figure
out the size of our own galaxy. Leavitt’s observation was a true surprise—a discovery in the classic sense—but one that came only after she’d spent years carefully comparing thousands of photos of these specks of light, looking for patterns
in the darkness.
The process of scientific discovery is not limited to professional scientists working in
labs. The everyday experience of deducing that your car won’t start because of a bad
fuel pump, or of figuring out that the centipedes in your backyard prefer shady rocks
shares fundamental similarities with classically scientific discoveries like working out
DNA’s double helix. These activities all involve making observations and analyzing
evidence—and they all provide the satisfaction of finding an answer that makes sense
of all the facts. In fact, some psychologists argue that the way individual humans
learn (especially as children) bears a lot of similarity to the progress of science: both
involve making observations, considering evidence, testing ideas, and holding on to
those that work.
Photo of Henrietta Leavitt provided by the American Association of Variable Star Observers (AAVSO).
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
4
A science checklist
So what, exactly, is science? Well, science turns out to be difficult to define precisely.
(Philosophers have been arguing about it for decades!) The problem is that the term
“science” applies to a remarkably broad set of human endeavors, from developing lasers, to analyzing the factors that affect human decision-making.
To get a grasp on what science is, we’ll look at a checklist that summarizes key characteristics of science and compare it to a prototypical case of science in action: Ernest
Rutherford’s investigation into the structure of the atom. Then, we’ll look at some other cases that are less “typical” examples of science to see how they measure up and
what characteristics they share.
This checklist provides a guide for what sorts of activities are encompassed by science, but since the boundaries of science are not clearly defined, the list should not be
interpreted as all-or-nothing. Some of these characteristics are particularly important
to science (e.g., all of science must ultimately rely on evidence), but others are less
central. For example, some perfectly scientific investigations may run into a dead end
and not lead to ongoing research. Use this checklist as a reminder of the usual features of science. If something doesn’t meet most of these characteristics, it shouldn’t
be treated as science.
Science asks questions about the
natural world
Science studies the natural world. This includes the components of the physical
universe around us like atoms, plants, ecosystems, people, societies and galaxies, as
well as the natural forces at work on those
things. In contrast, science cannot study supernatural forces and explanations. For example, the idea that a supernatural afterlife
exists is not a part of science since this afterlife operates outside the rules that govern
the natural world.
Anything in the natural world—from exotic ecosystems to urban smog—can be
the subject of scientific inquiry.
Cococino National Forest photo by Gerald and Buff Corsi © California Academy of Sciences; Jupiter photo by NASA/JPL/
Space Science Institute; photo of smoggy skyline by EPA; fungus photo by Dr. Robert Thomas and Dorothy B. Orr ©
California Academy of Sciences.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
5
Science can investigate all sorts of questions:
• When did the oldest rocks on earth form?
• Through what chemical reactions do fungi get energy from the nutrients they
absorb?
• What causes Jupiter’s red spot?
• How does smog move through the atmosphere?
Very few questions are off-limits in science—but the sorts of answers science can provide are limited. Science can only answer in terms of natural phenomena and natural processes. When we ask ourselves questions like, What is the meaning of life?
and Does the soul exist? we generally expect answers that are outside of the natural
world—and hence, outside of science.
A SCIENCE PROTOTYPE: RUTHERFORD
AND THE ATOM
In the early 1900s, Ernest Rutherford studied (among
other things) the organization of the atom—the fundamental particle of the natural world. Though atoms
cannot be seen with the naked eye, they can be studied
with the tools of science since they are part of the natural world.
Rutherford’s story continues as we examine each item
on the Science Checklist. To find out how this investigation measures up against the rest of the checklist, read
on.
Ernest Rutherford
Rutherford photo from the Library of Congress.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Science aims to explain and understand
Science as a collective institution aims to
produce more and more accurate natural explanations of how the natural world works,
what its components are, and how the world
got to be the way it is now. Classically, science’s main goal has been building knowledge and understanding, regardless of its
potential applications—for example, investigating the chemical reactions that an organic
compound undergoes in order to learn about
its structure. However, increasingly, scientific
research is undertaken with the explicit goal
of solving a problem or developing a technology, and along the path to that goal, new
knowledge and explanations are constructed.
For example, a chemist might try to produce
an antimalarial drug synthetically and in the
process, discover new methods of forming
bonds that can be applied to making other chemicals. Either way (so-called “pure” or
“applied” research), science aims to increase our understanding of how the natural
world works.
The knowledge that is built by science is always open
to question and revision. No scientific idea is ever
once-and-for-all “proved.” Why not? Well, science is
constantly seeking new evidence, which could reveal
problems with our current understandings. Ideas that
we fully accept today may be rejected or modified in
light of new evidence discovered tomorrow. For examA coelacanth
ple, up until 1938, paleontologists accepted the idea
that coelacanths (an ancient fish) went extinct at the time that they last appear in the
fossil record—about 80 million years ago. But that year, a live coelacanth was discovered off the coast of South Africa, causing scientists to revise their ideas and begin to
investigate how this animal survives in the deep sea.
Despite the fact that they are subject to change, scientific ideas are reliable. The ideas
that have gained scientific acceptance have done so because they are supported by
many lines of evidence. These scientific explanations continually generate expectations that hold true, allowing us to figure out how entities in the natural world are likely to behave (e.g., how likely it is that a child will inherit a particular genetic disease)
and how we can harness that understanding to solve problems (e.g., how electricity,
wire, glass, and various compounds can be fashioned into a working light bulb). For
example, scientific understandings of motion and gases allow us to build airplanes that
reliably get us from one airport to the next. Though the knowledge used to design airplanes is technically provisional, time and time again, that knowledge has allowed us
to produce airplanes that fly. We have good reason to trust scientific ideas: they work!
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
7
A SCIENCE PROTOTYPE: RUTHERFORD AND THE ATOM
Ernest Rutherford’s investigations were aimed at understanding a small, but illuminating, corner of the natural world: the atom. He investigated this world using
alpha particles, which are helium atoms stripped of their electrons. Rutherford
had found that when a beam of these tiny, positively-charged alpha particles is
fired through gold foil, the particles don’t stay on their beeline course, but are deflected (or “scattered”) at different angles. Rutherford wanted to figure out what
this might tell him about the layout of an atom.
Rutherford’s story continues as we examine each item on the Science Checklist.
To find out how this investigation measures up against the rest of the checklist,
read on.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Science works with testable ideas
Only testable ideas are within the purview of
science. For an idea to be testable, it must
logically generate specific expectations—
in other words, a set of observations that
we could expect to make if the idea were
true and a set of observations that would
be inconsistent with the idea and lead you
to believe that it is not true. For example,
consider the idea that a sparrow’s song is
genetically encoded and is unaffected by the
environment in which it is raised, in comparison to the idea that a sparrow learns
the song it hears as a baby. Logical reasoning about this example leads to a specific
set of expectations. If the sparrow’s song
were indeed genetically encoded, we would
expect that a sparrow raised in the nest of
a different species would grow up to sing a
sparrow song like any other member of its own species. But if, instead, the sparrow’s
song were learned as a chick, raising a sparrow in the nest of another species should
produce a sparrow that sings a non-sparrow song. Because they generate different
expected observations, these ideas are testable. A scientific idea may require a lot of
reasoning to work out an appropriate test, may be difficult to test, may require the
development of new technological tools to test, or may require one to make independently testable assumptions to test—but to be scientific, an idea must be testable,
somehow, someway.
If an explanation is equally compatible with all possible observations, then it is not
testable and hence, not within the reach of science. This is frequently the case with
ideas about supernatural entities. For example, consider the idea that an all-powerful
supernatural being controls our actions. Is there anything we could do to test that
idea? No. Because this supernatural being is all-powerful, anything we observe could
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
9
be chalked up to the whim of that being. Or not. The point is that we can’t use the
tools of science to gather any information about whether or not this being exists—so
such an idea is outside the realm of science.
A SCIENCE PROTOTYPE: RUTHERFORD AND THE ATOM
Before 1910, Ernest Rutherford and
many other scientists had the idea that
the positive charge and the mass of an
atom were evenly distributed throughout the whole atom, with electrons
scattered throughout. You can imagine
this model of the atom as a loosely
packed snowball (the positive mass
of the atom) with a few tiny grains of
sand (the electrons) scattered throughout. The idea that atoms are arranged
in this way can be tested by firing an
alpha particle beam through a piece of
gold foil. If the idea were correct, then
the positive mass in the gold foil would
be relatively diffuse (the loosely packed
snow) and would allow the alpha particles to pass through the foil with only minor scattering.
Rutherford’s story continues as we examine each item on the Science Checklist.
To find out how this investigation measures up against the rest of the checklist,
read on.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Science relies on evidence
Ultimately, scientific ideas must not only be
testable, but must actually be tested—preferably with many different lines of evidence by
many different people. This characteristic is
at the heart of all science. Scientists actively
seek evidence to test their ideas—even if
the test is difficult and means, for example,
spending years working on a single experiment, traveling to Antarctica to measure carbon dioxide levels in an ice core, or collecting
DNA samples from thousands of volunteers
all over the world. Performing such tests is
so important to science because in science,
the acceptance or rejection of a scientific
idea depends upon the evidence relevant to
it—not upon dogma, popular opinion, or tradition. In science, ideas that are not supported by evidence are ultimately rejected. And
ideas that are protected from testing or are only allowed to be tested by one group
with a vested interest in the outcome are not a part of good science.
A SCIENCE PROTOTYPE: RUTHERFORD AND THE ATOM
Ernest Rutherford’s lab tested the idea that an atom’s positive mass is spread out
diffusely by firing an alpha particle beam through a piece of gold foil, but the evidence resulting from that experiment was a complete surprise: most of the alpha
particles passed through the gold foil without changing direction much as expected, but some of the alpha particles came bouncing back in the opposite direction,
as though they had struck something dense and solid in the gold foil. If the gold
atoms were really like loosely packed snowballs, all of the alpha particles should
have passed through the foil, but they did not!
From this evidence, Rutherford concluded that their snowball model of
the atom had been incorrect, even
though it was popular with many
other scientists. Instead, the evidence
suggested that an atom is mostly
empty space and that its positive
charge is concentrated in a dense
mass at its core, forming a nucleus.
When the positively charged alpha
particles were fired at the gold foil,
most of them passed through the
empty space of the gold atoms with
little deflection, but a few of them
ran smack into the dense, positively
charged nucleus of a gold atom and
were repelled straight back (like what
would happen if you tried to make the
north poles of two strong magnets touch). The idea that atoms have positively
charged nuclei was also testable. Many independent experiments were performed
by other researchers to see if the idea fit with other experimental results.
Rutherford’s story continues as we examine each item on the Science Checklist.
To find out how this investigation measures up against the rest of the checklist,
read on.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
11
Science is embedded in the scientific
community
The progress of science depends on interactions within the scientific community—that is,
the community of people and organizations
that generate scientific ideas, test those
ideas, publish scientific journals, organize
conferences, train scientists, distribute research funds, etc. This scientific community
provides the cumulative knowledge base that
allows science to build on itself. It is also responsible for the further testing and scrutiny
of ideas and for performing checks and balances on the work of community members.
In addition, much scientific research is collaborative, with different people bringing
their specialized knowledge to bear on different aspects of the problem. For example, a
2006 journal article on regional variations in
the human genome was the result of a collaboration between 43 people from the U.K.,
Japan, the U.S., Canada, and Spain! Even Charles Darwin, who initially investigated
the idea of evolution through natural selection while living almost as a hermit at his
country estate, kept up a lively correspondence with his peers, sending and receiving
numerous letters dealing with his ideas and the evidence relevant to them.
In rare cases, scientists do actually
work in isolation. Gregor Mendel, for
example, figured out the basic principles
of genetic inheritance as a secluded
monk with very little scientific interaction. However, even in such cases,
research must ultimately involve the
scientific community if that work is to
have any impact on the progress of science. In Mendel’s case, the ultimate
involvement of the scientific community
through his published work was critical because it allowed other scientists
to evaluate those ideas independently,
investigate new lines of evidence, and
develop extensions of his ideas. This
community process may be chaotic and
slow, but it is also crucial to the progress of science.
Scientists sometimes work alone and sometimes work
together, but communication within the scientific
community is always important.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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A SCIENCE PROTOTYPE: RUTHERFORD AND THE ATOM
Though Ernest Rutherford came up with
the idea that atoms have positively
charged nuclei, the research that led to
this idea was a collaborative effort: Rutherford was assisted by Hans Geiger, and
the critical alpha-scattering experiment
was actually carried out by Ernest Marsden, an undergraduate student working in
Rutherford’s lab.
Furthermore, after his discovery of the
Ernest Rutherford (right) and Hans Geiger
layout of the atom, Rutherford published
in the physics laboratory at Manchester
a description of the idea and the relevant
University, England, circa 1912. Permission
of the Alexander Turnbull Library, Wellington,
evidence, releasing it to the scientific
New Zealand, must be obtained before any
community for scrutiny and evaluation.
re-use of this image. Reference number:
And scrutinize they did. Niels Bohr noPAColl-0091-1-011.
ticed a problem with Rutherford’s idea:
there was nothing keeping the orbiting electrons from spiraling into the nucleus
of the atom, causing the whole thing to collapse! Bohr modified Rutherford’s basic
model by proposing that electrons had set energy levels, which helped solve the
problem and earned Bohr a Nobel Prize. Since then, many other scientists have
built on and modified Bohr’s model.
Lithium atoms, diagrammed in the Rutherford
and Bohr models. Rutherford’s model does not
differentiate between any of the electrons, while
Bohr’s places electrons into orbits with set energy
levels.
Rutherford’s story continues as we examine each item on the Science Checklist.
To find out how this investigation measures up against the rest of the checklist,
read on.
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Scientific ideas lead to ongoing research
Science is an ongoing endeavor. It did not
end with the most recent edition of your college physics textbook and will not end even
once we know the answers to big questions,
such as how our 20,000 genes interact to
build a human being or what dark matter is.
So long as there are unexplored and unexplained parts of the natural world, science
will continue to investigate them.
Most typically in science, answering one
question inspires deeper and more detailed
questions for further research. Similarly,
coming up with a fruitful idea to explain a
previously anomalous observation frequently
leads to new expectations and areas of research. So, in a sense, the more we know,
the more we know what we don’t yet know.
As our knowledge expands, so too does our awareness of what we don’t yet understand. For example, James Watson and Francis Crick’s proposal that DNA takes the
form of a double helix helped answer a burning question in biology about the chemical structure of DNA. And while it helped answer one question, it also generated
new expectations (e.g., that DNA is copied via base pairing), raised many new questions (e.g., how does DNA store information?), and contributed to whole new fields
of research (e.g., genetic engineering). Like Watson and Crick’s work, most scientific research generates new expectations, inspires new questions, and leads to new
discoveries.
A SCIENCE PROTOTYPE: RUTHERFORD AND THE ATOM
Niels Bohr
Niels Bohr built upon Ernest Rutherford’s work to develop
the model of the atom most commonly portrayed in textbooks: a nucleus orbited by electrons at different levels.
Despite the new questions it raised (e.g., how do orbiting
electrons avoid violating the rules of electricity and magnetism when they don’t spiral into the nucleus?), this
model was powerful and, with further modification, led to
a wide range of accurate predictions and new discoveries: from predicting the outcome of chemical reactions,
to determining the composition of distant stars, to conceiving of the atomic bomb.
Rutherford’s story continues as we examine each item on the Science Checklist.
To find out how this investigation measures up to the last item of the checklist,
read on.
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Participants in science behave scientifically
Science is sometimes misconstrued as an
elite endeavor in which one has to be a
member of “the club” in order to be taken
seriously. That’s a bit misleading. In fact, science is now open to anyone (regardless of
age, gender, religious commitment, physical
ability, ethnicity, country of origin, political
views, nearsightedness, favorite ice cream
flavor—whatever!) and benefits tremendously from the expanding diversity of perspectives offered by its participants. However,
science only works because the people involved with it behave “scientifically”—that is,
behave in ways that push science forward.
But what exactly does one have to do to behave scientifically? Here is a scientist’s
code of conduct:
1)Pay attention to what other people have already done. Scientific knowledge
is built cumulatively. If you want to discover exciting new things, you need to
know what people have already discovered before you. This means that scientists
study their fields extensively to understand the current state of knowledge.
2)Expose your ideas to testing. Strive to describe and perform the tests that
might suggest you are wrong and/or allow others to do so. This may seem like
shooting yourself in the foot but is critical to the progress of science. Science
aims to accurately understand the world, and if ideas are protected from testing,
it’s impossible to figure out if they are accurate or inaccurate!
3)Assimilate the evidence. Evidence is the ultimate arbiter of scientific
ideas. Scientists are not free to ignore evidence. When faced with evidence
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contradicting his or her idea, a scientist may suspend judgment on that idea
pending more tests, may revise or reject the idea, or may consider alternate
ways to explain the evidence, but ultimately, scientific ideas are sustained by evidence and cannot be propped up if the evidence tears them down.
4)Openly communicate ideas and tests to others. Communication is important
for many reasons. If a scientist keeps knowledge to her- or himself, others cannot build upon those ideas, double-check the work, or devise new ways to test
the ideas.
5)Play fair: Act with scientific integrity. Hiding evidence, selectively reporting
evidence, and faking data directly thwart science’s main goal—to construct accurate knowledge about the natural world. Hence, maintaining high standards of
honesty, integrity, and objectivity is critical to science.
A SCIENCE PROTOTYPE: RUTHERFORD AND THE ATOM
Ernest Rutherford and his colleagues acted in ways that moved science forward:
• They understood the relevant knowledge in their field. Rutherford had
studied physics for more than 20 years when he proposed the idea of the
nucleus.
• They exposed their ideas to testing. Even though his original view of the
atom suggested that no backscattering should occur, Rutherford decided to
look for backscattered alpha particles anyway, just to be thorough.
• They assimilated the evidence. When their experimental results did not support the “snowball” model of the atom, instead of writing those results off as
an anomaly, they modified their original ideas in light of the new evidence.
• They openly communicated their ideas so that other physicists could test
them as well. Rutherford published the experimental results, a description of
his reasoning, and the idea of the nucleus in 1911 in a scientific journal.
• They acted with scientific integrity. In his paper on the topic, Rutherford assigned credit fairly (citing the contributions of his colleagues, Geiger and
Marsden) and reported his results honestly—even when experimental results
and his theoretical calculations did not match up perfectly.
The scientists involved with this investigation lived up to the five points in the scientist’s code of conduct. In this way—and judging by the other items on the Science Checklist—this investigation of atomic structure is well within the purview of
science.
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Beyond physics, chemistry, and biology
We’ve seen that scientific research generally
meets a set of key characteristics: it focuses
on improving our understanding of the natural world, works with testable ideas that can
be verified with evidence, relies on the scientific community, inspires ongoing research,
and is performed by people who behave
scientifically. While not all scientific investigations line up perfectly with the Science
Checklist, science, as an endeavor, strives
to embody these features. Ernest Rutherford’s discovery of the atomic nucleus, for
example, satisfied those characteristics quite
neatly. But how would a less stereotypically
“scientific” investigation—one that wouldn’t
show up in a high school science textbook—
measure up against the Science Checklist?
To find out, we’ll look at an example from the
field of psychology …
Beyond the prototype: Animal psychology
Most of us have probably wondered how other animals think and experience the world
(e.g, is Fido really happy to see me or does he just want a treat?)—but can that curiosity be satisfied by science? After all, how could we ever test an idea about how
another animal thinks? In the 1940s, psychologist Edward Tolman investigated a related question using the methods of science. He wanted to know how rats successfully navigate their surroundings—for example, a maze containing a hidden reward.
Tolman suspected that rats would build mental maps of the maze as they investigated
it (forming a mental picture of the layout of the maze), but many of his colleagues
thought that rats would learn to navigate the maze through stimulus-response, associating particular cues with particular outcomes (e.g., taking this tunnel means I get a
piece of cheese) without forming any big picture of the maze.
Here’s how Tolman’s investigation measures up against our checklist:
Natural world?
The brains of rats and their workings are a part of the natural world, as is the behavior of rats.
Aims to explain?
Tolman aimed to explain how rats navigate their surroundings.
Testable ideas?
The two ideas about how rats navigate (mental maps vs. stimulus-response) are
testable, but figuring out how to test them required some clever and logical thinking
about experimental design. To test these ideas, Tolman and his colleagues trained rats
in a maze which offered them many different tunnels to enter first. One of the tunnels
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twisted and turned but consistently led to the reward, and the rats quickly learned to
go down that tunnel. Then the experimenters blocked the entrance to the reward tunnel. What would the rats do? Tolman reasoned that if the rats were navigating with a
mental map, they would pick another tunnel that, according to their mental map of
the maze, led in the direction of the food. But if the rats were navigating via stimulusresponse, Tolman reasoned that they would choose the tunnel closest to the original
reward tunnel, regardless of where it led, since that was closest to the stimulus with
the pay-off.
Relies on evidence?
Tolman and his colleagues tested the mental map idea with several experiments, including the tunnel experiment described above. In that experiment, they found that
most of the rats picked a tunnel that led in the direction of the food, instead of one
close to the original reward tunnel. The evidence supported the idea that rats navigate
using something like a mental map.
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Scientific community?
Tolman published many papers on this topic in scientific journals in order to explain
his experiments and the evidence relevant to them to other psychologists.
Ongoing research?
This research is a small part of a much larger body of ongoing psychological research
about how organisms learn and make decisions based on their representations of the
world.
Scientific behavior?
Edward Tolman and his colleagues acted with scientific integrity and behaved in ways
that push science forward. They accurately reported their results and allowed others
to test their ideas.
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Science in disguise
Our Science Checklist fits well with a wide range of investigations—from developing an Alzheimer’s drug, to dissecting the
structure of atoms, to probing the neurology of human emotion. Even endeavors far from one’s typical picture of science,
like figuring out how best to teach English as a second language or examining the impact of a government deficit on the
economy, can be addressed by science.
Disguised as science
However, other human endeavors, which might at first seem
like science, are actually not very much like science at all. For
example, the Intelligent Design movement promotes the idea
that many aspects of life are too complex to have evolved
without the intervention of an intelligent cause—assumed by most proponents to be a
supernatural being, like God. Promoters of this idea are interested in explaining what
we observe in the natural world (the features of living things), which does align well
with the aims of science. However, because Intelligent Design relies on the action of
an unspecified “intelligent cause,” it is not a testable idea. Furthermore, the movement itself has several other characteristics that reveal it to be non-science.
Teaching is an example of
a challenge that can be
addressed by science.
Western astrology aims to explain and predict events on Earth in terms of the positions of the sun, planets, and constellations; hence, like science, astrology focuses on
explaining the natural world. However, in many other ways, astrology is not much like
science at all.
Western astrology is not science.
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Science has limits: A few things that
science does not do
Science is powerful. It has generated the knowledge that allows us to call a friend
halfway around the world with a cell phone, vaccinate a baby against polio, build a
skyscraper, and drive a car. And science helps us answer important questions like
which areas might be hit by a tsunami after an earthquake, how did the hole in the
ozone layer form, how can we protect our crops from pests, and who were our evolutionary ancestors? With such breadth, the reach of science might seem to be endless,
but it is not. Science has definite limits.
Science doesn’t make moral judgments
When is euthanasia the right thing to do?
What universal rights should humans have?
Should other animals have rights? Questions like these are important, but scientific
research will not answer them. Science can
help us learn about terminal illnesses and
the history of human and animal rights—
and that knowledge can inform our opinions and decisions. But ultimately, individual
people must make moral judgments. Science helps us describe how the world is, but it
cannot make any judgments about whether that state of affairs is right, wrong, good,
or bad.
Science doesn’t make aesthetic
judgments
Science can reveal the frequency of a
G-flat and how our eyes relay information about color to our brains, but science cannot tell us whether a Beethoven
symphony, a Kabuki performance, or a
Jackson Pollock painting is beautiful or
dreadful. Individuals make those decisions for themselves based on their own aesthetic criteria.
Science doesn’t tell you how to use scientific knowledge
Although scientists often care deeply about
how their discoveries are used, science itself
doesn’t indicate what should be done with
scientific knowledge. Science, for example,
can tell you how to recombine DNA in new
ways, but it doesn’t specify whether you
should use that knowledge to correct a genetic disease, develop a bruise-resistant
apple, or construct a new bacterium. For almost any important scientific advance, one
can imagine both positive and negative ways that knowledge could be used. Again,
science helps us describe how the world is, and then we have to decide how to use
that knowledge.
Science doesn’t draw conclusions
about supernatural explanations
Do gods exist? Do supernatural entities
intervene in human affairs? These questions may be important, but science won’t
help you answer them. Questions that deal
with supernatural explanations are, by
definition, beyond the realm of nature—
and hence, also beyond the realm of what can be studied by science. For many, such
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questions are matters of personal faith and spirituality.
Moral judgments, aesthetic judgments, decisions about applications of science, and
conclusions about the supernatural are outside the realm of science, but that doesn’t
mean that these realms are unimportant. In fact, domains such as ethics, aesthetics,
and religion fundamentally influence human societies and how those societies interact
with science. Neither are such domains unscholarly. In fact, topics like aesthetics, morality, and theology are actively studied by philosophers, historians, and other scholars. However, questions that arise within these domains generally cannot be resolved
by science.
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Science in sum
In this section, we’ve seen that, though
hard to define concisely, science has a
handful of key features that set it apart
from other areas of human knowledge.
However, the net cast by science is wide.
The Science Checklist matches up to a
diverse set of human endeavors—from uncovering the fundamental particles of the
universe, to studying the mating behavior
of lobsters, to investigating the effects of
different economic policies. We’ve also
seen that science has limits: some questions that are an important part of the human experience are not answerable within
the context of science.
So science isn’t everything, but it is important. Science helps us construct knowledge
about the natural world—knowledge that
can then be harnessed to improve our lives and solve problems. How does science do
it? To find out, read on …
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How science works
The Scientific Method is traditionally presented in the first chapter of science textbooks as a simple recipe for performing scientific investigations. Though many useful points are embodied in this method, it can easily be misinterpreted as linear and
“cookbook”: pull a problem off the shelf, throw in an observation, mix in a few questions, sprinkle on a hypothesis, put the whole mixture into a 350° experiment—and
voila, 50 minutes later you’ll be pulling a conclusion out of the oven! That might work
if science were like Hamburger Helper®, but science is complex and cannot be reduced to a single, prepackaged recipe.
The linear, stepwise representation of the process of science is simplified, but it does
get at least one thing right. It captures the core logic of science: testing ideas with
evidence. However, this version of the scientific method is so simplified and rigid that
it fails to accurately portray how real science works. It more accurately describes how
science is summarized after the fact—in textbooks and journal articles—than how science is actually done.
The simplified, linear scientific method implies that scientific studies follow an
unvarying, linear recipe.
But in reality, in their work, scientists engage in many different activities in many
different sequences. Scientific investigations often involve repeating the same steps
many times to account for new information and ideas.
The simplified, linear scientific method implies that science is done by individual
scientists working through these steps in isolation.
But in reality, science depends on interactions within the scientific community. Different parts of the process of science may be carried out by different people at different times.
The simplified, linear scientific method implies that science has little room for
creativity.
But in reality, the process of science is exciting, dynamic, and unpredictable. Science
relies on creative people thinking outside the box!
The simplified, linear scientific method implies that science concludes.
But in reality, scientific conclusions are always revisable if warranted by the evidence. Scientific investigations are often ongoing, raising new questions even as old
ones are answered.
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The real process of science
The process of science, as represented here, is the opposite of “cookbook” (to see the
full complexity of the process, roll your mouse over each element). In contrast to the
linear steps of the simplified scientific method, this process is non-linear:
•The process of science is iterative.
Science circles back on itself so that useful ideas are built upon and used to learn
even more about the natural world. This often means that successive investigations of a topic lead back to the same question, but at deeper and deeper levels.
Let’s begin with the basic question of how biological inheritance works. In the
mid-1800s, Gregor Mendel showed that inheritance is particulate—that information is passed along in discrete packets that cannot be diluted. In the early 1900s,
Walter Sutton and Theodor Boveri (among others) helped show that those particles of inheritance, today known as genes, were located on chromosomes. Experiments by Frederick Griffith, Oswald Avery, and many others soon elaborated on
this understanding by showing that it was the DNA in chromosomes which carries
genetic information. And then in 1953, James Watson and Francis Crick, again
aided by the work of many others, provided an even more detailed understanding
of inheritance by outlining the molecular structure of DNA. Still later in the 1960s,
Marshall Nirenberg, Heinrich Matthaei, and others built upon this work to unravel
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the molecular code that allows DNA to encode proteins. And it doesn’t stop there.
Biologists have continued to deepen and extend our understanding of genes, how
they are controlled, how patterns of control themselves are inherited, and how
they produce the physical traits that pass from generation to generation.
•The process of science is not predetermined.
Any point in the process leads to many possible next steps, and where that next
step leads could be a surprise. For example, instead of leading to a conclusion
about tectonic movement, testing an idea about plate tectonics could lead to an
observation of an unexpected rock layer. And that rock layer could trigger an interest in marine extinctions, which could spark a question about the dinosaur extinction—which might take the investigator off in an entirely new direction.
At first this process might seem overwhelming. Even within the scope of a single investigation, science may involve many different people engaged in all sorts of different activities in different orders and at different points in time—it is simply much more
dynamic, flexible, unpredictable, and rich than many textbooks represent it as. But
don’t panic! The scientific process may be complex, but the details are less important
than the big picture …
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A blueprint for scientific investigations
The process of science involves many layers of complexity, but the key points of that
process are straightforward:
There are many routes into the process—from serendipity (e.g., being hit on the
head by the proverbial apple), to concern over a practical problem (e.g., finding a new
treatment for diabetes), to a technological development (e.g., the launch of a more
advanced telescope)—and scientists often begin an investigation by plain old poking
around: tinkering, brainstorming, trying to make some new observations, chatting
with colleagues about an idea, or doing some reading.
Scientific testing is at the heart of the process. In science, all ideas are tested
with evidence from the natural world, which may take many different forms—from
Antarctic ice cores, to particle accelerator experiments, to detailed descriptions of sedimentary rock layers. You can’t move through the process of science without examining how that evidence reflects on your ideas about how the world works—even if that
means giving up a favorite hypothesis.
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The scientific community helps ensure science’s accuracy. Members of the scientific community (i.e., researchers, technicians, educators, and students, to name a
few) play many roles in the process of science, but are especially important in generating ideas, scrutinizing ideas, and weighing the evidence for and against them.
Through the action of this community, science is self-correcting. For example, in the
1990s, John Christy and Roy Spencer reported that temperature measurements taken
by satellite, instead of from the Earth’s surface, seemed to indicate that the Earth was
cooling, not warming. However, other researchers soon pointed out that those measurements didn’t correct for the fact that satellites slowly lose altitude as they orbit
and that once these corrections are made, the satellite measurements were much
more consistent with the warming trend observed at the surface. Christy and Spencer
immediately acknowledged the need for that correction.
The process of science is intertwined with society. The process of science both
influences society (e.g., investigations of X-rays leading to the development of CT
scanners) and is influenced by society (e.g., a society’s concern about the spread of
HIV leading to studies of the molecular interactions within the immune system).
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Exploration and discovery
The early stages of a scientific investigation often rely on making observations, asking questions, and initial experimentation—essentially poking around—but the routes
to and from these stages are diverse. Intriguing observations sometimes arise in
surprising ways, as in the discovery of radioactivity, which was inspired by the observation that photographic plates (an early version of camera film) stored next to uranium salts were unexpectedly exposed. Sometimes interesting observations (and the
investigations that follow) are suddenly made possible by the development of a new
technology. For example, the launch of the Hubble Space Telescope in 1990 allowed
astronomers to make deeper and more focused observations of our universe than
were ever before possible. These observations ultimately led to breakthroughs in areas as diverse as star and planet formation, the nature of black holes, and the expansion of the universe.
Observations like this image from the Hubble Telescope can lead to further breakthroughs.
Sometimes, observations are clarified and questions arise through discussions with
colleagues and reading the work of other scientists—as demonstrated by the discovery
of the role of chlorofluorocarbons (CFCs) in ozone depletion …
Hubble image provided by NASA, ESA, and A. Nota (STScI/ESA)
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EXPLORING AEROSOLS
In 1973, chemists had observed that CFCs were being released into the environment from aerosol cans, air conditioners, and other sources, but it was discussions with his
colleague and advisor, Sherwood Rowland, that led Mario
Molina to ask what their ultimate fate was. Since CFCs
were rapidly accumulating in the atmosphere, the question
was intriguing, but before he could tackle the issue (which
would ultimately lead to a Nobel Prize and an explanation
for the hole in the ozone layer), Molina needed more information. He had to learn more about other scientists’ studies of atmospheric chemistry, and what he learned pointed
to the disturbing fate of CFCs.
Mario Molina
Furthermore, though observation and questioning are essential to the process of science, on their own, they are not enough to launch a scientific investigation; generally,
scientists also need scientific background knowledge—all the information and understandings they’ve picked up from their scientific training in school, supplemented by
discussions with colleagues and reviews of the scientific literature. As in Mario Molina’s
story, an understanding of what other scientists have already figured out about a particular topic is critical to the process. This background knowledge allows scientists to
recognize revealing observations for what they are, to make connections between ideas
and observations, and to figure out which questions can be fruitfully tackled with available tools. The importance of content knowledge to the process of science helps explain
why science is often mischaracterized as a static set of facts contained in textbooks—
science is a process, but one that relies on accumulated knowledge to move forward.
THE SCIENTIFIC STATE OF MIND
Some scientific discoveries are chalked up to the serendipity of being in the right place at the right time
to make a key observation—but rarely does serendipity alone lead to a new discovery. The people who
turn lucky breaks into breakthroughs are generally
those with the background knowledge and scientific
ways of thinking needed to make sense of the lucky
observation. For example, in 1896, Henri Becquerel
Henri Becquerel
made a surprising observation. He found that photographic plates stored next to uranium salts were
spotted, as though they’d been exposed to light
rays—even though they had been kept in a dark
drawer. Someone else, with a less scientific state of
mind and less background knowledge about physics,
might have cursed their bad luck and thrown out the
ruined plates. But Becquerel was intrigued by the observation. He recognized it as something scientifically
interesting, went on to perform follow-up experiments
that traced the source of the exposure to the uraniThe ruined photo plate that got
um, and in the process, discovered radioactivity. The
Becquerel thinking
key to this story of discovery lies partly in Becquerel’s
instigating observation, but also in his way of thinking. Along with the relevant
background knowledge, Becquerel had a scientific state of mind. Sure, he made
some key observations — but then he dug into them further, inquiring why the
plates were exposed and trying to eliminate different potential causes of the exposure to get to the physical explanation behind the happy accident.
Mario Molina photo by Donna Coveney/MIT
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Observation beyond our eyes
We typically think of observations as having been seen “with our own eyes,” but in
science, observations can take many forms. Of course, we can make observations directly by seeing, feeling, hearing, and smelling, but we can also extend and refine our
basic senses with tools: thermometers, microscopes, telescopes, radar, radiation sensors, X-ray crystallography, mass spectroscopy, etc. And these tools do a better job of
observing than we can! Further, humans cannot directly sense many of the phenomena that science investigates (no amount of staring at this computer screen will ever
let you see the atoms that make it up or the UV radiation that it emits), and in such
cases, we must rely on indirect observations facilitated by tools. Through these tools,
we can make many more observations much more precisely than those our basic
senses are equipped to handle.
Tools like the Hubble Space Telescope, microscopes and submersibles help us to observe the natural world.
Observations yield what scientists call data. Whether the observation is an experimental result, radiation measurements taken from an orbiting satellite, an infrared recording of a volcanic eruption, or just noticing that a certain bird species always thumps
the ground with its foot while foraging — they’re all data. Scientists analyze and interpret data in order to figure out how those data inform their hypotheses and theories.
Do they support one idea over others, help refute an idea, or suggest an entirely new
explanation? Though data may seem complex and be represented by detailed graphs
or complex statistical analyses, it’s important to remember that, at the most basic
level, they are simply observations.
Observations inspire, lend support to, and help refute scientific hypotheses and theories. However, theories and hypotheses (the fundamental structures of scientific
knowledge) cannot be directly read off of nature. A falling ball (no matter how detailed
our observations of it may be) does not directly tell us how gravity works, and collecting observations of all the different finch species of the Galapagos Islands does not directly tell us how their beaks evolved. Scientific knowledge is built as people come up
with hypotheses and theories, repeatedly test them against observations of the natural world, and continue to refine those explanations based on new ideas and observations. Observation is essential to the process of science, but it is only half the picture.
Hubble image provided by NASA; microscope photo from Scott Bauer/USDA; submersible photo from NOAA Ocean Explorer
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Testing scientific ideas
Testing hypotheses and theories is at the core of the process of science. Any aspect
of the natural world could be explained in many different ways. It is the job of science
to collect all those plausible explanations and to use scientific testing to filter through
them, retaining ideas that are supported by the evidence and discarding the others.
You can think of scientific testing as occurring in two logical steps: (1) if the idea is
correct, what would we expect to see, and (2) does that expectation match what we
actually observe? Ideas are supported when actual observations (i.e., results) match
expected observations and are contradicted when they do not match.
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TESTING IDEAS ABOUT CHILDBED FEVER
As a simple example of how scientific testing works, consider the case of Ignaz Semmelweis, who worked as a doctor
on a maternity ward in the 1800s. In his ward, an unusually high percentage of new mothers died of what was then
called childbed fever. Semmelweis considered many possible
explanations for this high death rate. Two of the many ideas
that he considered were (1) that the fever was caused by
mothers giving birth lying on their backs (as opposed to on
their sides) and (2) that the fever was caused by doctors’
unclean hands (the doctors often performed autopsies immediately before examining women in labor).
Ignaz Semmelweis
He tested these ideas by considering what expectations each idea generated. If
it were true that childbed fever were caused by giving birth on one’s back, then
changing procedures so that women labored on their sides should lead to lower
rates of childbed fever. Semmelweis tried changing the position of labor, but the
incidence of fever did not decrease; the actual observations did not match the
expected results. If, however, childbed fever were caused by doctors’ unclean
hands, having doctors wash their hands thoroughly with a strong disinfecting
agent before attending to women in labor should lead to lower rates of childbed
fever. When Semmelweis tried this, rates of fever plummeted; the actual observations matched the expected results, supporting the second explanation.
Testing in the tropics
Let’s take a look at another, very different, example of scientific testing: investigating the origins of coral atolls in
the tropics. Consider the atoll Eniwetok
(Anewetak) in the Marshall Islands—an
oceanic ring of exposed coral surrounding a central lagoon. From the 1800s up
until today, scientists have been trying
to learn what supports atoll structures
beneath the water’s surface and exactly
how atolls form. Eniwetok could have
formed in several ways:
A coral atoll
Hypothesis 1: Coral only grows near the surface
of the ocean where light penetrates—so perhaps
the coral that makes up Eniwetok grew in a ring
atop an underwater mountain, which was itself
built by oceanic debris or uplifted through tectonic action.
Hypothesis 2: Another possibility is that Eniwetok originally grew around a volcanic island,
which then sunk beneath the surface of the water as the reef continued to grow to the surface.
Underwater volcanic activity (i.e., hotspots) can
produce an island in the middle of the ocean, as
cooled lava builds up around the hotspot. However, tectonic plate movement eventually carries
the island off the hotspot, keeping the island from being built up further. Meanwhile,
coral organisms grow in a ring in the shallow waters surrounding the exposed volcanic island. As time passes, erosion and tectonic action cause the island to sink slowly
(or subside), and as it does, it takes the coral ring with it. However, coral are living
Atoll photo from yunmeng’s photostream on flickr (CC BY-NC-SA 2.0)
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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organisms and grow their colonies upwards as their substrate sinks. Over time, the island could sink deep below the surface of the water, while the coral continue to thrive,
constantly growing towards the surface in their original ring configuration.
Which is a better explanation for Eniwetok? Is it built atop an underwater mountain,
or is it a tower of coral growing atop an ancient sunken volcano? Which of these explanations is best supported by the evidence?
If Eniwetok grew atop an underwater mountain, then we would expect the atoll to be
made up of a relatively thin layer of coral on top of limestone or basalt. But if it grew
upwards around a subsiding island, then we would expect the atoll to be made up of
many hundreds of feet of coral on top of volcanic rock. When geologists drilled into
Eniwetok in 1951 as part of a survey preparing for nuclear weapons tests, the drill
bored through more than 4000 feet (1219 meters) of coral before hitting volcanic basalt! The actual observation contradicted the underwater mountain explanation and
matched the subsiding island explanation, supporting that idea. Of course, many other
lines of evidence also shed light on the origins of coral atolls, but the surprising depth
of coral on Eniwetok was particularly convincing to many geologists.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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The logic of scientific arguments
Taken together, the expectations generated by a scientific idea and the actual observations relevant to those expectations form what we’ll call a scientific argument. This is
a bit like an argument in a court case—a logical description of what we think and why
we think it. A scientific argument uses evidence to make a case for whether a scientific idea is accurate or inaccurate. For example, the idea that illness in new mothers can
be caused by doctors’ dirty hands generates the expectation that illness rates should
go down when doctors are required to wash their hands before attending births. When
this test was actually performed in the 1800s, the results matched the expectations,
forming a strong scientific argument in support of the idea—and hand-washing!
Though the elements of a scientific argument (scientific idea, expectations generated by the idea, and relevant observations)
are always related in the same logical way,
in terms of the process of science, those elements may be assembled in different orders.
Sometimes the idea comes first and then
scientists go looking for the observations
that bear on it. Sometimes the observations
are made first, and they suggest a particular
idea. Sometimes the idea and the observations are already out there, and someone
comes along later and figures out that the
two might be related to one another.
Testing ideas with evidence may seem like
plain old common sense—and at its core,
it is!—but there are some subtleties to the
process:
•Ideas can be tested in many ways. Some tests are relatively straightforward
(e.g., raising 1000 fruit flies and counting how many have red eyes), but some require a lot of time (e.g., waiting for the next appearance of Halley’s Comet), effort
(e.g., painstakingly sorting through thousands of microfossils), and/or the development of specialized tools (like a particle accelerator).
•Evidence can reflect on ideas in many different ways.
•There are multiple lines of evidence and many criteria to consider in evaluating an idea.
•All testing involves making some assumptions.
Despite these details, it’s important to remember that, in the end, hypotheses and
theories live and die by whether or not they work—in other words, whether they are
useful in explaining data, generating expectations, providing satisfying explanations,
inspiring research questions, answering questions, and solving problems. Science filters through many ideas and builds on those that work!
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Tactics for testing ideas
Experiments are one way to test some sorts of ideas, but science doesn’t live on experiment alone. There are many other ways to scientifically test ideas too …
What are experiments?
An experiment is a test that involves manipulating some factor in a system in order
to see how that affects the outcome. Ideally, experiments also involve controlling as
many other factors as possible in order to isolate the cause of the experimental results. Experiments can be quite simple tests set up in a lab—like rolling a ball down
different inclines to see how the angle affects the rolling time. But large-scale experiments can also be performed out in the real world—for example, classic experiments
in ecology involved removing a species of barnacles from intertidal rocks on the Scottish coast to see how that would affect other barnacle species over time. But whether
they are large- or small-scale, performed in the lab or in the field, and require years
or mere milliseconds to complete, experiments are distinguished from other sorts of
tests by their reliance on the intentional manipulation of some factors and, ideally, the
control of others.
Experiments can even take place on the ocean floor. In this case, a remotelyoperated vehicle retrieves basalt cubes that were placed almost a year earlier
as potential sites for new coral attachment. The experiment is examining how
coral reproduce and disperse.
Natural experiments
Some aspects of the natural world aren’t
manipulable, and hence can’t be studied
with direct experiments. We simply can’t
go back in time and introduce finches to
three separate island groups to see how
they evolve. We can’t move the planets
around to see how their orbits would be
altered by a new configuration. And we
can’t cause volcanoes to erupt in order to
investigate how they affect the ecosystems that surround them. However, such
ancient, distant, and large-scale phenomena can be studied with the methods
described below, and in many cases,
we can observe the results of natural
experiments on these systems. Natural
experiments occur when the universe, in
Though we can’t experimentally manipulate
phenomena like volcanoes, we can carefully observe
the outcomes of these natural experiments. In this
photo, a geologist takes a lava sample from the
Kilauea volcano in Hawaii.
Remotely-operated vehicle photo provided by NOAA; Kilauea photo provided by U.S. Department of Interior, U.S. Geological
Survey
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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a sense, performs an experiment for us—that is, the relevant experimental set-up already exists, and all we have to do is observe the results.
More than just experiments
A T. rex tooth can
tell us a lot about
what this animal
ate.
For many ideas in science, testing via experiment is impossible,
inappropriate, or only part of the picture. In those cases, testing
is often a matter of making the right observations. For example,
we can’t actually experiment on distant stars in order to test ideas
about which nuclear reactions occur within them, but we can test
those ideas by building sensors that allow us to observe what forms
of radiation the stars emit. Similarly, we can’t perform experiments
to test ideas about what T. rex ate, but we can test those ideas by
making detailed observations of their fossilized teeth and comparing
those to the teeth of modern organisms that eat different foods. And
of course, many ideas can be tested by both experiment and through
straightforward observation. For example, we can test ideas about
how chlorofluorocarbons interact with the ozone layer by performing
chemical experiments in a lab and through observational studies of
the atmosphere.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Digging into data
Evaluating an idea in light of the evidence
should be simple, right? Either the results
match the expectations generated by the
idea (thus, supporting it) or they don’t
(thus, refuting it). Sometimes the process
is relatively simple (e.g., drilling into a coral
atoll either reveals a thick layer of coral or
a thin veneer), but often it is not. The real
world is messy and complex, and often, interpreting the evidence relating to an idea
is not so clear-cut. To complicate things
further, we often have to weigh multiple
lines of evidence that are all relevant to the
validity of a particular idea.
Tests typically generate what scientists think of as raw
data—unaltered observations, descriptions, or measurements—but those must be analyzed and interpreted. Data
become evidence only when they have been interpreted
in a way that reflects on the accuracy or inaccuracy of
a scientific idea. For example, an investigation of the
evolutionary relationships among crustaceans, insects,
millipedes, spiders, and their relatives might tell us the
genetic sequence of a particular gene for each organism.
This is raw data, but what does it mean? A long series of
the As, Ts, Gs, and Cs that make up genetic sequences
don’t, by themselves, tell us whether insects are more
closely related to crustaceans or to spiders. Instead,
those data must be analyzed through statistical calculations, tabulations, and/or visual representations. In this
case, a biologist might begin to analyze the genetic data
by aligning the different sequences, highlighting similarities and differences, and performing calculations to compare the different sequences. Only then can she interpret
the results and figure out whether or not they support the
hypothesis that insects are more closely related to crustaceans than to spiders.
Furthermore, the same data may be interpreted in different ways. So another scientist
could analyze the same genetic data in a new way and come to a different conclusion
about the relationships between insects, crustaceans, and spiders. Ultimately, the scientific community will come to a consensus about how a set of data should be interpreted,
but this process may take some time and usually involves additional lines of evidence.
CALCULATING CONFIDENCE
Interpreting test results often means dealing with uncertainty and error. “Now,
hold on,” you might be thinking, “I thought that science was supposed to build
knowledge and decrease uncertainty and error.” And that’s true; however, when
scientists draw a conclusion or make a calculation, they frequently try to give
a statistical indication of how confident they are in the result. In everyday language, uncertainty and error mean that the answer is unclear or that a mistake
has been made. However, when scientists talk about uncertainty and error, they
are usually indicating their level of confidence in a number. So reporting a temperature to be 98.6° F (37° C) with an uncertainty of plus or minus 0.4° F actually means that we are highly confident that the true temperature falls between
98.2 and 99.0° F.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Reviewing test results
Scientists typically weigh multiple competing ideas about how something works and
try to figure out which of those is most accurate based on the evidence. However,
looking at the results of a test (whether the test is an experiment or another sort of
study) often leads to surprises.
•Evidence may lend support to one hypothesis over others. For example,
drilling into coral atolls and discovering a layer of coral thousands of feet thick
clearly lent support to the idea that coral atolls form around subsiding volcanic islands, although, of course, many other lines of evidence also helped support that
idea over competing explanations.
•Evidence may help rule out some hypotheses. Similarly, the results of the
atoll drilling project helped refute a different idea—that atolls grow atop underwater mountains built up by oceanic debris, which would have fit with the observation of a thin layer of coral.
•Evidence may lead to the revision of a hypothesis. For example, experiments and observations had long supported the idea that light consists of waves,
but in 1905, Einstein showed that a well known (and previously unexplained) phenomenon—the photoelectric effect—made perfect sense if light consisted of discrete particles. This led physicists to modify their ideas about the nature of light:
light was both wave-like and particle-like.
The photoelectric effect is a phenomenon in which electrons are
emitted by a metal surface when certain frequencies of light
strike it. This effect didn’t make sense until Einstein suggested
that light consisted of particles with discrete amounts of energy.
•Evidence may reveal a faulty assumption, causing the scientist to revise
his or her assumptions and possibly redesign the test. For example, in the
1970s, geologists tried to test ideas about the timing of the transition between
the Cretaceous and Tertiary periods by measuring the amount of iridium in the
transitional rock layer. The test relied on the assumption that iridium was deposited at a low but constant, normal rate. However, to their surprise, the rock layer
contained unusually large amounts of iridium, indicating that their original test
design had been based on the false assumption of a low and constant deposition
rate.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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•Evidence may be so surprising that a wholly new hypothesis or new research question is inspired. Along similar lines, the unexpected discovery of
large amounts of iridium at the Cretaceous-Tertiary boundary eventually inspired
a new hypothesis about a different topic—that the end-Cretaceous mass extinction was triggered by a catastrophic asteroid impact.
•Evidence may be inconclusive, failing to support any particular explanation over another. For example, many biologists have investigated the anatomy
and genetic sequences of the arthropods (crustaceans, insects, millipedes, spiders, and their relatives) in order to figure out how these groups are related. So
far, the results have been inconclusive, not consistently supporting a single view
of their interrelationships. Biologists continue to collect more evidence in order to
resolve the question.
New evidence can feed back into the process of science in many ways. Most importantly, new evidence helps us evaluate ideas. To learn more about how science evaluates ideas, read on …
Asteroid image provided by Don Davis and NASA
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Competing ideas: A perfect fit for the
evidence
We’ve seen that evaluating an idea in science is not always a matter of one key experiment and a definitive result. Scientists often consider multiple ideas at once and
test those ideas in many different ways. This process generates multiple lines of evidence relevant to each idea. For example, two competing ideas about coral atoll formation (island subsidence vs.
formation on debris-topped
underwater mountains) were
evaluated based on multiple
lines of evidence, including
observations of reef and atoll
shapes, island geology, studies of the distribution of planktonic debris, and reef drilling.
Furthermore, different lines
of evidence are assembled
cumulatively over time as different scientists work on the
problem and as new technologies are developed. Because
of this, the evaluation of scientific ideas is provisional.
Science is always willing to
resurrect or reconsider an idea
if warranted by new evidence.
It’s no wonder then that the evaluation of scientific ideas is iterative and depends
upon interactions within the scientific community. Ideas that are accepted by that
community are the best explanations we have so far for how the natural world works.
But what makes one idea better than another? How do we judge the accuracy of an
explanation? The most important factors have to do with evidence—how well our actual observations fit the expectations generated by the hypothesis or theory. The better
the match, the more likely the hypothesis or theory is accurate.
•Scientists are more likely to trust ideas that more closely explain the actual observations. For example, the theory of general relativity explains why
Mercury’s orbit around the Sun shifts as much as it does with each lap (Mercury is
close enough to the Sun that it passes through the area where space-time is dimpled by the Sun’s mass). Newtonian mechanics, on the other hand, suggests that
this aberration in Mercury’s orbit should be much smaller than what we actually
observe. So general relativity more closely explains our observations of Mercury’s
orbit than does Newtonian mechanics.
Mercury’s orbit around the sun shifts a bit with each lap, which
can be explained by the theory of general relativity.
•Scientists are more likely to trust ideas that explain more disparate observations. For example, many scientists in the 17th and 18th centuries were
Atoll satellite image by NASA/Goddard Space Flight Center; coral core sample photo by Jeff Anderson, Florida Keys National
Marine Sanctuary
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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puzzled by the presence of marine fossils high in the Alps of Europe. Some tried
to explain their presence with a massive flood, but this didn’t address why these
fossils were of animals that had gone extinct. Other scientists suggested that sea
level had risen and dropped several times in the past, but had no explanation for
the height of the mountains. However, the theory of plate tectonics helped explain
all these disparate observations (high mountains, uplifted chunks of the seafloor,
and rocks so ancient that they contained the fossils of long extinct organisms)
and many more, including the locations of volcanoes and earthquakes, the shapes
of the continents, and huge rifts in the ocean’s floor.
•Scientists are more likely to trust ideas that explain observations that
were previously inexplicable, unknown, or unexpected. For an example, see
Rudolph Marcus’s story below …
JUMPING ELECTRONS!
As chemical reactions go, electron transfers
might seem to be minor players: an electron jumps between molecules without even
breaking a chemical bond. Nevertheless,
such reactions are essential to life. Photosynthesis, for example, depends on passing electrons from one molecule to another
to transfer energy from light to molecules
that can be used by a cell. Some of these
reactions proceed at breakneck speeds, and Rudolph Marcus
others are incredibly slow—but why should
two reactions, both involving a single electron transfer, vary in speed?
In the 1950s, Rudolph Marcus and his colleagues developed a simple mathematical explanation for how the rate of the reaction changes based on the amount
of free energy absorbed or released by the system. The explanation fit well
with actual observations that had been made at the time, but it also generated
an unintuitive expectation—that some reactions, which release a lot of energy,
should proceed surprisingly slowly, and should slow down as the energy released
increases. It was a bit like suggesting that for most ski slopes, a steeper incline
means faster speeds, but that on the very steepest slopes, skiers will slide down
slowly! The expectation generated by Marcus’s idea was entirely unanticipated,
but nevertheless, almost 25 years later, experiments confirmed the surprising expectation, supporting the idea and winning Marcus the Nobel Prize.
What happens when science can’t immediately produce the evidence relevant to an
idea? Absence of evidence isn’t evidence of absence. Science doesn’t reject an idea
just because the relevant evidence isn’t readily available. Sometimes, we have to wait
for an event (e.g., the next solar eclipse), hope for a key discovery (e.g., transitional
whale fossils in the deserts of Pakistan), or try to develop a new technology (e.g., a
more powerful telescope), and until then, must suspend our judgment of an idea.
Rudolph Marcus image provided by the California Institute of Technology
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Competing ideas: Other considerations
In evaluating scientific ideas, evidence is the main arbiter; however, sometimes the
available evidence supports several different hypotheses or theories equally well. In
those cases, science often applies other criteria to evaluate the explanations. Though
these are more like rules of thumb than firm standards, scientists are more likely to
put their trust in ideas that:
• generate more specific expectations (i.e., are more testable). For example,
a hypothesis about hurricane formation that generates more specific expectations
about the conditions under which they are likely to form might be preferred over
one that just suggests what time of year they should be common.
• can be more broadly applied. For example, a theory about the nature of force
that applies to both macroscopic interactions (e.g., the pull of Earth’s gravity on
an apple) and subatomic interactions (e.g., between protons and electrons) might
be preferred over one that only applies to interactions between large objects.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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• are more parsimonious. For example, a hypothesis about the evolutionary relationships among hummingbird species that involves only 70 evolutionary changes
might be preferred over one that postulates 200 changes.
THE PRINCIPLE OF PARSIMONY
The principle of parsimony suggests that when two explanations fit the observations equally well, a simpler explanation should be preferred over a more convoluted and complex explanation. For a hypothetical illustration, imagine that we
have only a few lines of evidence in a case of cookie jar pilfering: a broken and
empty cookie jar, a crumb trail leading to the doggie door, and Fido’s bellyache.
Perhaps Fido stole the cookies, or perhaps it was all a set-up: the parrot knocked
the jar off the table and ate the cookies, the cat tracked the crumbs to the door,
and Fido has a bellyache because he got into the neighbor’s garbage can. Both
explanations fit all the available evidence—but which is more parsimonious?
• are more consistent with well-established theories in neighboring fields.
For example, a major argument against the theory of evolution when Darwin first
proposed it was that the theory didn’t mesh with what was known about the age
of the Earth at the time. Physicists had estimated the Earth to be just 100 million
years old, a length of time that was deemed insufficient for evolution to account
for the diversity of life on Earth today. However, as our understanding of geology and physics have improved, the age of the Earth has been more accurately
pegged at several billion years old—a view that squares well with the idea that all
life on Earth evolved from a common ancestor.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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• generate more new ideas. For example, evolutionary biology not only helps us
understand the history of life on Earth, but also generates useful ideas that can
be applied to many fields—most notably in medicine, agriculture, and conservation. The power of evolution to generate fruitful ideas in many other fields reinforces its value as a theory.
All this might seem complex, but it’s important to keep the main point in mind. These
criteria are just guidelines for identifying ideas that work—ideas that fit the evidence,
generate new expectations, inspire further research, and seem to be accurate explanations for how the world works!
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Making assumptions
Much as we might like to avoid it, all scientific tests involve making assumptions—
many of them justified. For example, imagine a very simple test of the hypothesis that
substance A stops bacterial growth. Some Petri dishes are spread with a mixture of
substance A and bacterial growth medium, and others are spread with a mixture of
inert substance B and bacterial growth medium. Bacteria are spread on all the Petri
dishes, and one day later, the plates are examined to see which fostered the growth
of bacterial colonies and which did not. This test is straightforward, but still relies on
many assumptions: we assume that the bacteria can grow on the growth medium, we
assume that substance B does not affect bacterial growth, we assume that one day is
long enough for colonies to grow, and we assume that the color pen we use to mark
the outside of the dishes is not influencing bacterial growth.
Technically, these are all assumptions, but they are perfectly reasonable ones that
can be tested. The scientist performing the experiment described above would justify
many of her assumptions by performing additional tests in parallel with the experimental ones. For example, she would separately test whether substance B affects bacterial growth to check that it was indeed inert as she’d assumed. Other assumptions
are justified by past tests performed by other scientists. For instance, the question of
whether or not bacteria can grow on the growth medium would have been studied by
many previous researchers. And some assumptions might remain untested simply because all of our knowledge about the field suggests that the assumption is a safe one
(e.g., we know of no reason why bacteria should multiply faster when their dishes are
marked with a red, rather than a green, pen). All tests involve assumptions, but most
of these are assumptions that can and have been verified separately.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Nevertheless, when evaluating an idea in light of test results, it’s important to keep in
mind the test’s assumptions and how well-supported they are. If an expectation generated by an idea is not borne out in a test, it might be because the idea is wrong and
should be rejected, or it might be that the idea is right, but an assumption of the test
has been violated. And if the test results end up lending support to the idea, it might
be because the idea is correct and should be accepted, or it might be because a violated assumption has produced a false positive result.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Analysis within the scientific community
The stereotype of a scientist (a recluse who speaks in a jumble of technical jargon)
doesn’t exactly paint a picture of someone whose work depends on communication
and community, but in fact, interactions within the scientific community are essential
components of the process of science. Scientists don’t work in isolation. Though they
sometimes work alone (fussing over an experiment in the lab, trekking through the
Amazon, scribbling on a notepad at a desk), scientists are just as likely to be found
emailing colleagues, arguing with other scientists over coffee, sitting in on a lab meeting, or preparing conference presentations and journal articles. In science, even those
few working entirely on their own must ultimately share their work for it to become
part of the lasting body of scientific knowledge.
In terms of the process of science, members of the community play several essential
and direct roles:
Fact checker/critic: the community evaluates evidence and
ideas. The scrutiny of the scientific community helps ensure
that evidence meets high standards of quality, that all relevant lines of evidence are explored, and that judgments are
not based on flawed reasoning.
Innovator/visionary: the community generates new ideas.
Interactions within a diverse and creative community spark
ideas about new lines of evidence, new interpretations of existing data, new applications, new questions, and alternate
explanations—all of which help science move forward.
Watchdog/whistleblower: the community helps eliminate
bias and fraud by keeping watchful eye. Though fraud is rare
and bias often unintentional, the occasional cases of such offenses are detected through the scrutiny and ongoing work of
the scientific community.
Cheerleader/taskmaster: the community motivates scientists. The community offers the prospects of recognition,
esteem, and a scientific legacy—payoffs which help motivate
many scientists in their investigations.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Interactions within the scientific community and the scrutiny they entail take time and
can slow the process of science. However, these interactions are crucial because they
help ensure that science provides us with more and more accurate and useful descriptions of how the world works.
So how, exactly, does the scientific community manage to play all these challenging
roles? To learn more about key features of community analysis—publication, peer review, and replication—read on …
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Publish or perish?
Among academics, the maxim “publish or
perish” (i.e., publish your research or risk
losing your job) is a threatening reminder
of the importance of publication. Despite
its cynicism, the phrase makes an important point: publishing findings, hypotheses, theories, and the lines of reasoning
and evidence relevant to them is critical
to the progress of science. The scientific
community can only fulfill its roles as fact
checker, visionary, whistleblower, and
cheerleader if it has trusted information
about the work of community members.
Scientists distribute information about
their ideas in many ways—informally communicating with colleagues, making presentations at conferences, writing books,
etc.—but among these different modes of
communication, peer-reviewed journal articles are especially important.
What’s in a scientific journal article?
A journal article is a formal, souped-up version of the standard high school lab report.
In journal articles, scientists (usually a group of collaborators) describe a study and
report any details one might need to evaluate that study—background information,
data, statistical results, graphs, maps, explanations of how the study was performed
and how the researchers drew their conclusions, etc. These articles are published in
scientific journals either in print or on the internet. Print journals look much like any
magazine, except that they are chock full of firsthand reports of scientific research.
Journals distribute scientific information to researchers all around the world so that
they can keep current in their fields and evaluate the work of their peers.
Journal articles neaten up the messy process of science, presenting ideas, evidence,
and reasoning in a way that’s easy to understand—in contrast to the often circuitous
(and sometimes tedious) process of science. For an example, check out Walter Alvarez’s story below …
UNTANGLING A TWISTED PATH
In 1980, in the journal Science, Walter Alvarez and
his colleagues published a scientific article describing
their controversial new hypothesis that the dinosaur
extinction was triggered by a massive asteroid impact. Despite its splashy and novel topic, the article
laid out its hypothesis and evidence in the conventional way—linearly—which allowed colleagues in
geology and paleontology to quickly understand and
evaluate the research. Though helpful for scientific
Walter Alvarez
communication, this linear presentation can give the
impression that an investigation has been plotted out
from the beginning—but in fact, Alvarez’s study was far from linear. He stumbled
onto his hypothesis unexpectedly, originally setting out to study the tectonic
movements of the Italian peninsula. After an intriguing series of twists, turns,
false starts, inspirations, and rejected hypotheses, he and his colleagues found
that they had completed a rather different, but compelling, investigation.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Scrutinizing science: Peer review
Peer review does the same thing for science that the “inspected by #7” sticker does
for your t-shirt: provides assurance that someone who knows what they’re doing has
double-checked it. In science, peer review typically works something like this:
1)A group of scientists completes a study and writes it up in the form of an article.
They submit it to a journal for publication.
2)The journal’s editors send the article to several other scientists who work in the
same field (i.e., the “peers” of peer review).
3)Those reviewers provide feedback on the article and tell the editor whether or
not they think the study is of high enough quality to be published.
4)The authors may then revise their article and resubmit it for consideration.
5)Only articles that meet good scientific standards (e.g., acknowledge and build
upon other work in the field, rely on logical reasoning and well-designed studies,
back up claims with evidence, etc.) are accepted for publication.
Peer review and publication are time-consuming, frequently involving more than a
year between submission and publication. The process is also highly competitive.
For example, the highly-regarded journal Science accepts less than 8% of the articles it receives, and The New England Journal of Medicine publishes just 6% of its
submissions.
Peer-reviewed articles provide a trusted form of scientific communication. Even if you
are unfamiliar with the topic or the scientists who authored a particular study, you can
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trust peer-reviewed work to meet certain standards of scientific quality. Since scientific knowledge is cumulative and builds on itself, this trust is particularly important. No
scientist would want to base their own work on someone else’s unreliable study! Peerreviewed work isn’t necessarily correct or conclusive, but it does meet the standards
of science. And that means that once a piece of scientific research passes through
peer review and is published, science must deal with it somehow—perhaps by incorporating it into the established body of scientific knowledge, building on it further, figuring out why it is wrong, or trying to replicate its results.
PEER REVIEW: NOT JUST SCIENCE
Many fields outside of science use peer review to ensure quality. Philosophy journals, for example, make publication decisions based on the reviews of other philosophers, and the same is true of scholarly journals on topics as diverse as law,
art, and ethics. Even those outside the research community often use some form
of peer review. Figure-skating championships may be judged by former skaters
and coaches. Wine-makers may help evaluate wine in competitions. Artists may
help judge art contests. So while peer review is a hallmark of science, it is not
unique to science.
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Copycats in science: The role of replication
Scientists aim for their studies’ findings to be replicable—so that, for example, an
experiment testing ideas about the attraction between electrons and protons should
yield the same results when repeated in different labs. Similarly, two different researchers studying the same dinosaur bone in the same way should come to the same
conclusions regarding its measurements and composition. This goal of replicability
makes sense. After all, science aims to reconstruct the unchanging rules by which the
universe operates, and those same rules apply, 24 hours a day, seven days a week,
from Sweden to Saturn, regardless of who is studying them. If a finding can’t be replicated, it suggests that our current understanding of the study system or our methods
of testing are insufficient.
Does this mean that scientists are constantly repeating what others before them have
already done? No, of course not—or we would never get anywhere at all. The process
of science doesn’t require that every experiment and every study be repeated, but
many are, especially those that produce surprising or particularly important results. In
some fields, it is standard procedure for a scientist to replicate his or her own results
before publication in order to ensure that the findings were not due to some fluke or
factors outside the experimental design.
The desire for replicability is part of the reason that scientific papers almost always include a methods section, which describes exactly how the researchers performed the
study. That information allows other scientists to replicate the study and to evaluate
its quality, helping ensure that occasional cases of fraud or sloppy scientific work are
weeded out and corrected.
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Benefits of science
The process of science is a way of building knowledge about the universe — constructing new ideas that illuminate the world around us. Those ideas are inherently
tentative, but as they cycle through the process of science again and again and are
tested and retested in different ways, we become increasingly confident in them. Furthermore, through this same iterative process, ideas are modified, expanded, and
combined into more powerful explanations. For example, a few observations about
inheritance patterns in garden peas can—over many years and through the work of
many different scientists—be built into the broad understanding of genetics offered
by science today. So although the process of science is iterative, ideas do not churn
through it repetitively. Instead, the cycle actively serves to construct and integrate
scientific knowledge.
And that knowledge is useful for all sorts of things: from designing bridges, to slowing climate change, to prompting frequent hand washing during flu season. Scientific
knowledge allows us to develop new technologies, solve practical problems, and make
informed decisions—both individually and collectively. Because its products are so useful, the process of science is intertwined with those applications:
•New scientific knowledge may lead to
new applications.
For example, the discovery of the structure
of DNA was a fundamental breakthrough in
biology. It formed the underpinnings of research that would ultimately lead to a wide
variety of practical applications, including
DNA fingerprinting, genetically engineered
crops, and tests for genetic diseases.
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•New technological advances may lead to
new scientific discoveries.
For example, developing DNA copying and
sequencing technologies has led to important breakthroughs in many areas of biology,
especially in the reconstruction of the evolutionary relationships among organisms.
•Potential applications may motivate scientific investigations.
For example, the possibility of genetically
engineering bacteria to cheaply produce
cutting-edge malaria drugs has motivated
one researcher to continue his studies of
synthetic biology.
The process of science and you
This flowchart represents the process of formal science, but in fact, many aspects of
this process are relevant to everyone and can be used in your everyday life—even if
you are not an amateur or professional scientist. Sure, some elements of the process
really only apply to formal science (e.g., publication, feedback from the scientific community), but others are widely applicable to everyday situations (e.g., asking questions, gathering evidence, solving practical problems). Understanding the process of
science can help anyone develop a scientific outlook on life.
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Science at multiple levels
The process of science works at multiple levels—from the small scale (e.g., a comparison of the genes of three closely related North American butterfly species) to the large
scale (e.g., a half-century-long series of investigations of the idea that geographic
isolation of a population can trigger speciation). The process of science works in much
the same way whether embodied by an individual scientist tackling a specific problem,
question, or hypothesis over the course of a few months or years, or by a community
of scientists coming to agree on broad ideas over the course of decades and hundreds
of individual experiments and studies. Similarly, scientific explanations come at different levels:
Hypotheses
Hypotheses are proposed explanations for a fairly narrow set of phenomena. These
reasoned explanations are not guesses—of the wild or educated variety. When scientists formulate new hypotheses, they are usually based on prior experience, scientific
background knowledge, preliminary observations, and logic. For example, scientists
observed that alpine butterflies exhibit characteristics intermediate between two species that live at lower elevations. Based on these observations and their understanding
of speciation, the scientists hypothesized that this species of alpine butterfly evolved
as the result of hybridization between the two other species living at lower elevations.
Theories
Theories, on the other hand, are broad explanations for a wide range of phenomena.
They are concise (i.e., generally don’t have a long list of exceptions and special rules),
coherent, systematic, predictive, and broadly applicable. In fact, theories often integrate and generalize many hypotheses. For example, the theory of natural selection
broadly applies to all populations with some form of inheritance, variation, and differential reproductive success—whether that population is composed of alpine butterflies,
fruit flies on a tropical island, a new form of life discovered on Mars, or even bits in
a computer’s memory. This theory helps us understand a wide range of observations
(from the rise of antibiotic-resistant bacteria to the physical match between pollinators
and their preferred flowers), makes predictions in new situations (e.g., that treating
AIDS patients with a cocktail of medications should slow the evolution of the virus),
and has proven itself time and time again in thousands of experiments and observational studies.
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“JUST” A THEORY?
Occasionally, scientific ideas (such as biological evolution) are written off with the
putdown “it’s just a theory.” This slur is misleading and conflates two separate
meanings of the word theory: in common usage, the word theory means just a
hunch, but in science, a theory is a powerful explanation for a broad set of observations. To be accepted by the scientific community, a theory (in the scientific
sense of the word) must be strongly supported by many different lines of evidence. So biological evolution is a theory (it is a well-supported, widely accepted,
and powerful explanation for the diversity of life on Earth), but it is not “just” a
theory.
Words with both technical and everyday meanings often cause confusion. Even
scientists sometimes use the word theory when they really mean hypothesis or
even just a hunch. Many technical fields have similar vocabulary problems — for
example, both the terms work in physics and ego in psychology have specific
meanings in their technical fields that differ from their common uses. However,
context and a little background knowledge are usually sufficient to figure out
which meaning is intended.
Over-arching theories
Some theories, which we’ll call over-arching theories, are particularly important and
reflect broad understandings of a particular part of the natural world. Evolutionary
theory, atomic theory, gravity, quantum theory, and plate tectonics are examples of
this sort of over-arching theory. These theories have been broadly supported by multiple lines of evidence and help frame our understanding of the world around us.
Such over-arching theories encompass many subordinate theories and hypotheses,
and consequently, changes to those smaller theories and hypotheses reflect a refinement (not an overthrow) of the over-arching theory. For example, when punctuated
equilibrium was proposed as a mode of evolutionary change and evidence was found
supporting the idea in some situations, it represented an elaborated reinforcement of
evolutionary theory, not a refutation of it. Over-arching theories are so important because they help scientists choose their methods of study and mode of reasoning, connect important phenomena in new ways, and open new areas of study. For example,
evolutionary theory highlighted an entirely new set of questions for exploration: How
did this characteristic evolve? How are these species related to one another? How has
life changed over time?
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A MODEL EXPLANATION
Hypotheses and theories can be complex. For example, a particular hypothesis
about meteorological interactions or nuclear reactions might be so complex that
it is best described in the form of a computer program or a long mathematical
equation. In such cases, the hypothesis or theory may be called a model.
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Even theories change
Accepted theories are the best explanations available so far for how the world works.
They have been thoroughly tested, are supported by multiple lines of evidence, and
have proved useful in generating explanations and opening up new areas for research.
However, science is always a work in progress, and even theories change. How? We’ll
look at some over-arching theories in physics as examples:
• Classical mechanics
In the 1600s, building on the ideas of others, Isaac Newton constructed a theory
(sometimes called classical mechanics or Newtonian mechanics) that, with a simple set of mathematical equations, could explain the movement of objects both
in space and on Earth. This single explanation helped us understand both how a
thrown baseball travels and how the planets orbit the sun. The theory was powerful, useful, and has proven itself time and time again in studies; yet it wasn’t perfect …
• Special relativity
Classical mechanics was one-upped by Albert Einstein’s theory of special relativity.
In contrast to the assumptions of classical mechanics, special relativity postulated
that as one’s frame of reference (i.e., where you are and how you are moving)
changes, so too do measurements of space and time—so that, for example, a
person speeding away from Earth in a spacecraft will perceive the distance of the
spacecraft’s travel and the elapsed time of the trip to be different than would a
person sitting at Cape Canaveral. Special relativity was preferred because it explained more phenomena: it accounted for what was known about the movement
of large objects (from baseballs to planets) and helped explain new observations
relating to electricity and magnetism.
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• General relativity
Even special relativity was superseded by another theory. General relativity
helped explain everything that special relativity did, as well as our observations of
gravitational forces.
• Our next theory …
General relativity has been enormously successful and has generated unique expectations that were later borne out in observations, but it too seems up for a
change. For example, general relativity doesn’t mesh with what we know about
the interactions between extremely tiny particles (which the theory of quantum
mechanics addresses). Will physicists develop a new theory that simultaneously
helps us understand the interactions between the very large and the very small?
Time will tell, but they are certainly working on it!
All the theories described above worked—that is, they generated accurate expectations, were supported by evidence, opened up new avenues of research, and offered
satisfying explanations. Classical mechanics, by the way, is still what engineers use
to design airplanes and bridges, since it is so accurate in explaining how large (i.e.,
macroscopic) and slow (i.e., substantially slower than light) objects interact. Nevertheless, the theories described above did change. How? A well-supported theory may
be accepted by scientists, even if the theory has some problems. In fact, few theories
fit our observations of the world perfectly. There is usually some anomalous observation that doesn’t seem to fit with our current understanding. Scientists assume that
by working at such anomalies, they’ll either disentangle them to see how they fit with
the current theory or contribute to a new theory. And eventually that does happen: a
new or modified theory is proposed that explains everything that the old theory explained plus other observations that didn’t quite fit with the old theory. When that new
or modified theory is proposed to the scientific community, over a period of time (it
might take years), scientists come to understand the new theory, see why it is a superior explanation to the old theory, and eventually, accept the new theory.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Theory change is a community process of
feedback, experiment, observation, and communication. It usually involves interpreting
existing data in new ways and incorporating
those views with new results. It may depend
on a single definitive experiment or observation to change people’s views, or it may involve
many separate studies, eventually tipping the
balance of evidence in favor of the new theory.
The process may take some time since scientists don’t always recognize good ideas right
away, but eventually the scientific explanation
that is more accurate will win out. This process
of theory change often involves true scientific
controversy, which is healthy, sparks additional
research, and helps science move forward. True
scientific controversy involves disagreements
over how data should be interpreted, over
which ideas are best supported by the available evidence, and over which ideas are worth
investigating further.
SCIENTIFIC CONTROVERSY: TRUE OR FALSE?
Here, we’ve discussed true scientific controversy—a debate within the scientific
community over which scientific idea is more accurate and should be used as the
basis of future research. True scientific controversy involves competing scientific ideas that are evaluated according to the standards of science—i.e., fitting
the evidence, generating accurate expectations, offering satisfying explanations,
inspiring research, etc. However, occasionally, special interest groups try to misrepresent a non-scientific idea, which meets none of these standards, as inspiring
scientific controversy.
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Summing up the process
In this section, we’ve seen that the
real process of science is not much like
The Scientific Method often portrayed
in textbooks. As opposed to the simple
recipe of the linear scientific method,
the real process of science is exciting,
iterative, nonlinear, nuanced, depends
upon the scientific community, and is
intertwined with the society at large.
The real process of science proceeds at
multiple levels and sorts through many
ideas, retaining and building upon those
that work. However, despite all these
complications, the core of that process,
checking ideas against evidence from
the natural world, is straightforward.
© 2012 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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What has science done for you lately?
Plenty. If you think science doesn’t matter much to you, think again. Science affects
us all, every day of the year, from the moment we wake up, all day long, and through
the night. Your digital alarm clock, the weather report, the asphalt you drive on, the
bus you ride in, your decision to eat a baked potato instead of fries, your cell phone,
the antibiotics that treat your sore throat, the clean water that comes from your faucet, and the light that you turn off at the end of the day have all been brought to you
courtesy of science. The modern world would not be modern at all without the understandings and technology enabled by science.
Science affects us all, every day of the year.
To make it clear how deeply science is interwoven with our lives, just try imagining a
day without scientific progress. Just for starters, without modern science, there would
be:
• no way to use electricity. From Ben Franklin’s
studies of static and lightning in the 1700s, to
Alessandro Volta’s first battery, to the key discovery of the relationship between electricity and
magnetism, science has steadily built up our understanding of electricity, which today carries our
voices over telephone lines, brings entertainment
to our televisions, and keeps the lights on.
• no plastic. The first completely synthetic plastic
was made by a chemist in the early 1900s, and
since then, chemistry has developed a wide variety of plastics suited for all sorts of jobs, from
blocking bullets to making slicker dental floss.
Bus photo provided by SunLine Transit Agency; shopping photo by USDA; faucet photo by CDC; medicine photo by National Institute of
General Medical Sciences; light bulb photo by U.S. Climate Change Technology Program; phone photo by Maine.gov; photo of powerlines
provided by Warren Gretz/NREL.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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• no modern agriculture. Science has transformed the way we eat today. In the 1940s, biologists began developing high-yield varieties of
corn, wheat, and rice, which, when paired with
new fertilizers and pesticides developed by chemists, dramatically increased the amount of food
that could be harvested from a single field, ushering in the Green Revolution. These science-based
technologies triggered striking changes in agriculture, massively increasing the amount of food
available to feed the world and simultaneously transforming the economic structure of agricultural practices.
• no modern medicine. In the late 1700s, Edward
Jenner first convincingly showed that vaccination worked. In the 1800s, scientists and doctors
established the theory that many diseases are
caused by germs. And in the 1920s, a biologist
discovered the first antibiotic. From the eradication of smallpox, to the prevention of nutritional
deficiencies, to successful treatments for once
deadly infections, the impact of modern medicine
on global health has been powerful. In fact, without science, many people alive today would have instead died of diseases that are
now easily treated.
Scientific knowledge can improve the quality of life at many different levels—from the
routine workings of our everyday lives to global issues. Science informs public policy
and personal decisions on energy, conservation, agriculture, health, transportation,
communication, defense, economics, leisure, and exploration. It’s almost impossible to
overstate how many aspects of modern life are impacted by scientific knowledge. Here
we’ll discuss just a few of these examples.
Photo of soybean crop provided by Dave Warren/USDA; smallpox vaccine photo provided by James Gathany/CDC.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Fueling technology
Basic science fuels advances in technology, and technological innovations affect our
lives in many ways everyday. Because of science, we have complex devices like cars,
X-ray machines, computers, and phones. But the technologies that science has inspired include more than just hi-tech machines. The notion of technology includes any
sort of designed innovation. Whether a flu vaccine, the technique and tools to perform
open heart surgery, or a new system of crop rotation, it’s all technology. Even simple
things that one might easily take for granted are, in fact, science-based technologies:
the plastic that makes up a sandwich bag, the genetically-modified canola oil in which
your fries were cooked, the ink in your ballpoint pen, a tablet of ibuprofen—it’s all
here because of science.
Though the impact of technology on our lives is often clearly positive (e.g., it’s hard
to argue with the benefits of being able to effectively mend a broken bone), in some
cases the payoffs are less clear-cut. It’s important to remember that science builds
knowledge about the world, but that people decide how that knowledge should be
used. For example, science helped us understand that much of an atom’s mass is in
its dense nucleus, which stores enormous amounts of energy that can be released by
breaking up the nucleus. That knowledge itself is neutral, but people have chosen to
apply it in many different ways:
• Energy. Our understanding of this basic atomic structure has been used as the
basis of nuclear power plants, which themselves have many societal benefits
(e.g., nuclear power does not rely on non-renewable, polluting fossil fuels) and
costs (e.g., nuclear power produces radioactive waste, which must be carefully
stored for long periods of time).
• Medicine. That understanding has also been used in many modern medical applications (e.g., in radiation therapy for cancer and in medical imaging, which can
trace the damage caused by a heart attack or Alzheimer’s disease).
• Defense. During World War II, that knowledge also clued scientists and politicians in to the fact that atomic energy could be used to make weapons. Once a
political decision was made to pursue atomic weapons, scientists worked to develop other scientific knowledge that would enable this technology to be built.
Computer chip photo provided by NASA; lab research photo provided by James Gathany/CDC; International Space Station photo provided by
NASA; ibuprofen image comes from Bright_Star’s flickr page (CC BY-NC-ND 2.0); canola oil image comes from adpowers’s flickr page (CC BY
2.0); pen tip image comes from Tzatziki’s flickr page (CC BY-NC-SA 2.0).
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So scientific knowledge allows new technologies to be built, and those technologies, in
turn, impact society at many levels. For example, the advent of atomic weapons has
influenced the way that World War II ended, its aftermath, and the power plays between nations right up until today.
Rancho Seco nuclear reactor photo provided by Warren Gretz; x-ray photo provided by CDC/Libero Ajello; missile photo provided by DOE.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Science and technology on fast forward
Science and technology feed off of one another, propelling both forward. Scientific
knowledge allows us to build new technologies, which often allow us to make new
observations about the world, which, in turn, allow us to build even more scientific
knowledge, which then inspires another technology … and so on. As an example, we’ll
start with a single scientific idea and trace its applications and impact through several
different fields of science and technology, from the discovery of electrons in the 1800s
to modern forensics and DNA fingerprinting …
From cathodes to crystallography
We pick up our story in the late 1800s
with a bit of technology that no one
much understood at the time, but
which was poised to change the face
of science: the cathode ray tube (node
A in the diagram below). This was a
sealed glass tube emptied of almost all
air—but when an electric current was
passed through the tube, it no longer
A cathode ray tube from the early 1900s.
seemed empty. Rays of eerie light shot
across the tube. In 1897, physicists
would discover that these cathode rays were actually streams of electrons (B). The
discovery of the electron would, in turn, lead to the discovery of the atomic nucleus
in 1910 (C). On the technological front, the cathode ray tube would slowly evolve into
the television (which is constructed from a cathode ray tube with the electron beam
deflected in ways that produce an image on a screen) and, eventually, into many sorts
of image monitors (D and E). But that’s not all …
In 1895, the German physicist Wilhem Roentgen noticed that his cathode ray tube
seemed to be producing some other sort of ray in addition to the lights inside the
tube. These new rays were invisible but caused a screen in his laboratory to light up.
He tried to block the rays, but they passed right through paper, copper, and aluminum, but not lead. And not bone. Roentgen noticed that the rays revealed the faint
shadow of the bones in his hand! Roentgen had discovered X-rays, a form of electromagnetic radiation (F). This discovery would, of course, shortly lead to the invention
of the X-ray machine (G), which would in turn, evolve into the CT scan machine (H)—
both of which would become essential to non-invasive medical diagnoses. And the CT
scanner itself would soon be adopted by other branches of science—for neurological
research, archaeology, and paleontology, in which CT scans are used to study the interiors of fossils (I). Additionally, the discovery of X-rays would eventually lead to the
development of X-ray telescopes to detect radiation emitted by objects in deep space
(J). And these telescopes would, in turn, shed light on black holes, supernovas, and
the origins of the universe (K). But that’s not all …
The discovery of X-rays also pointed William and William Bragg (a father-son team) in
1913 and 1914 to the idea that X-rays could be used to figure out the arrangements
of atoms in a crystal (L). This works a bit like trying to figure out the size and shape
of a building based on the shadow it casts: you can work backwards from the shape
of the shadow to make a guess at the building’s dimensions. When X-rays are passed
through a crystal, some of the X-rays are bent or spread out (i.e., diffracted) by the
atoms in the crystal. You can then extrapolate backwards from the locations of the deflected X-rays to figure out the relative locations of the crystal atoms. This technique
is known as X-ray crystallography, and it has profoundly influenced the course of science by providing snapshots of molecular structures.
Perhaps most notably, Rosalind Franklin used X-ray crystallography to help uncover
the structure of the key molecule of life: DNA. In 1952, Franklin, like James Watson
Cathode ray tube photo provided by Henk Dijkstra © The Cathode Ray Tube site.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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and Francis Crick, was working on the structure of DNA—
but from a different angle. Franklin was painstakingly producing diffracted images of DNA, while Watson and Crick
were trying out different structures using tinker-toy models
of the component molecules. In fact, Franklin had already
proposed a double helical form for the molecule when, in
1953, a colleague showed Franklin’s most telling image to
Watson. That picture convinced Watson and Crick that the
molecule was a double helix and pointed to the arrangement of atoms within that helix. Over the next few weeks,
the famous pair would use their models to correctly work
out the chemical details of DNA (M).
The impact of the discovery of DNA’s structure on scientific
research, medicine, agriculture, conservation, and other
social issues has been wide-ranging—so much so, that it is
difficult to pick out which threads of influence to follow. To
choose just one, understanding the structure of DNA (along
with many other inputs) eventually allowed biologists to
develop a quick and easy method for copying very small
amounts of DNA, known as PCR—the polymerase chain
reaction (N). This technique (developed in the 1980s), in
turn, allowed the development of DNA fingerprinting technologies, which have become an important part of modern
criminal investigations (O).
As shown by the flowchart above, scientific knowledge (like
the discovery of X-rays) and technologies (like the invention of PCR) are deeply interwoven and feed off one another. In this case, tracing the influence of a single technology,
the cathode ray tube, over the course of a century has
taken us on a journey spanning ancient fossils, supernovas,
the invention of television, the atomic nucleus, and DNA
fingerprinting. And even this complex network is incomplete. Understanding DNA’s structure, for example, led to
many more advances besides just the development of PCR.
And similarly, the invention of the CT scanner relied on
much more scientific knowledge than just an understanding of how X-ray machines work. Scientific knowledge and
technology form a maze of connections in which every idea
is connected to every other idea through a winding path.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Making strides in medicine
A century ago, a diagnosis of juvenile diabetes was an almost certain death sentence.
Children affected by diabetes rarely lived more than a few years. However, thanks to
the discovery of insulin in the early 1920s, along with subsequent scientific breakthroughs in genetic engineering that allowed insulin to be mass-produced, that statistic has completely turned around: diabetics now live long lives.
Diabetes is just one of many diseases and health concerns for which science has
helped develop treatments, preventions, or cures. Without science, we wouldn’t know
how to make an X-ray machine, how to build an artificial knee, how to prevent nutritional deficiencies, how to ward off cholera and malaria, or even, at the most basic
level, that hand-washing can prevent the spread of germs. In many thousands of
ways, science has supplied us with tools to improve human health—not the least of
which has been medications to treat diseases …
MOLDY MIRACLE DRUGS
At his lab bench in 1928, biologist Alexander Fleming found that his research
had gone bad—moldy, in fact. One of his
plates of bacterial colonies had picked up
the tiny spores of a mold floating through
the air and was now growing a fuzzy
head of white fluff. Instead of tossing the
contaminated plate, Fleming took a close
look and noticed that the white fluff was
having a surprisingly powerful effect. The
mold, of course, was Penicillium, and it
was not only slowing the bacteria—it was
actually causing them to explode! Fleming immediately began experiments and
soon showed that the mold was able to
kill many bacterial strains, including those
that cause strep throat, staph infections,
pneumonia, syphilis, and gonorrhea. And
unlike other bacterial treatments available
at the time (like mercury and arsenic),
penicillin was non-toxic, exclusively attacking bacteria and leaving the body’s
own cells alone. It would take another decade for scientists to develop the means
of producing and purifying the drug efficiently, but when they did, it was a breakthrough, arriving just in time to treat
wounded World War II soldiers.
Alexander Fleming
One species of Penicillium is used in the
production of the antibiotic penicillin, but
others are important in cheese-making.
Another, like the one pictured here, causes an
AIDS-related illness.
Before long, other compounds like penicillin were discovered, ushering in the age
of antibiotics and saving millions of lives. Unfortunately, it would not last long.
Antibiotic-resistant bacteria rapidly evolved and were first documented just four
years after penicillin became widely available. Over the last 20 years, antibiotic
resistance has become an increasingly serious problem. Now, medical doctors
are again looking towards scientific research with the hope that the lab bench will
once more provide them with a silver bullet to fight bacterial infections.
Alexander Fleming photo courtesy of the National Library of Medicine; Penicillium photo courtesy of the CDC/ Dr. Libero Ajello.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Getting personal
You may not be an expert on microbiology, geology, or climatology, but even so, scientific knowledge may factor into your everyday decision-making. Science has implications for issues we face everyday—and while science doesn’t dictate which choice
is the right one, it does give us important background knowledge to inform our decisions. Here are just a few examples of everyday decisions informed by science:
To wash or not to wash. One hundred and seventy
years ago, hand-washing wasn’t an everyday ritual—
even for doctors working in both the morgue and the
maternity ward! However, since then, biologists have
developed the germ theory of disease, and research
has shown that hand-washing prevents the spread of
infection. A 2005 study found that promoting handwashing among children in low-income areas could reduce the incidence of diseases like pneumonia by fifty
percent! Though washing one’s hands might seem like
a simple habit today, it is so commonplace only because scientific knowledge has emphasized its benefits.
Which fish? Will you have the local tilapia or the orange roughy? Taste certainly factors into this decision,
as does cost. But what about science? Conservation
biology tells us that the orange roughy’s population
has been decimated by the seafood industry. Even
more worrisome, biologists have figured out that the
fish lives to be 100 years old and doesn’t begin to reproduce until it’s 20 years old, making it difficult for
the population to recover from over-fishing. Tilapia,
on the other hand, is farmed specifically for human
consumption and is not threatened. Which will you
choose?
Dodging disaster. Everyone needs a place to call
home, but where will yours be? If you’re considering a
house in earthquake country, you might want to take
a cue from seismologists and geologists: not all soil
types are the same. Scientists have determined that
some areas within earthquake zones are unusually
dangerous and damage-prone because of the possibility of liquefaction—a phenomenon in which shaking
causes soil particles to flow past one another easily,
like a liquid. In this case, science can point you towards a more stable and safe home.
Am I better yet? You’re over your strep throat and
feeling well again, so is it time to ditch the antibiotics? Well, you could, but evolutionary biology suggests
that stopping a course of antibiotics early encourages
the evolution of antibiotic resistant bacteria, by allowing those bacteria not quite killed off by the incomplete dose of antibiotics to preferentially survive and
reproduce. Those mildly resistant bacteria could come
back to haunt you or infect someone else, and if they
do, your original antibiotic may not work against the
new strain.
The orange roughy (top) and
tilapia (bottom) available on the
same menu have very different
conservation statuses.
Damage due to liquefaction after
an earthquake in Niigata, Japan in
1964.
Streptococcus bacteria
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Petroleum preferences. You’re in the market for a
new car—but which one? There are many considerations, including mileage. A car that gets better mileage means that you’ll pay less for gas. But geology
can shed even more light on the issue. The petroleum
necessary to make gas is a limited resource. The
Earth only has so much oil and geologists estimate
that we have already tapped much of that. The more
petroleum we use, the harder it becomes to find. The
harder petroleum is to find, the more expensive each
barrel of oil becomes, and the more you’ll be paying
at the gas pump! A car that conserves gas might be
more expensive now, but could end up paying off in
the long run.
A plug-in hybrid electric vehicle that
can run off of electricity generated
by renewable sources.
Hand washing photo provided by CDC/Kelly Thomas; orange roughy photo by W. Savary from the FDA Regulatory Fish Encyclopedia; tilapia
photo by B. Tenge from the FDA Regulatory Fish Encyclopedia; liquefaction photo provided by Earthquake Engineering Research Center;
Streptococcus bacteria provided by CDC/Janice Carr; plug-in hybrid electric car photo by Mike Linenberger/NREL.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Shaping society
Just as it shapes your personal decision-making, scientific knowledge also helps inform regulatory decision-making and policy—and the results of these decisions are
everywhere. In fact, they are so ubiquitous that you probably never even stop to
think about them. Why is your quart of milk decorated with a nutrition label? Why do
schools check students’ vaccination records? Why aren’t your new kitchen tiles made
of asbestos? Why is it illegal to pour your used motor oil down a storm drain? Because
of science, of course. Science informs policies that promote our health, safety, and environmental stewardship.
Policies that you confront every day are informed by science.
Science doesn’t dictate policy, but it does give us a “how-to” manual for reaching the
outcomes that we decide we want. For example:
• Want to get rid of polio? In the 1940s and 50s,
American society got behind efforts to prevent
and treat polio by donating to the organization
called the March of Dimes. Through the March of
Dimes, that societal concern financed research on
polio vaccines. Science provided us with the vaccine that made prevention possible, and it also
gave us an understanding of polio transmission
that shaped our approach to administering the
vaccine. If we wanted to truly eradicate the disA child in India is given an oral polio
ease, only a massive vaccination effort would do
vaccine.
the trick. Today, a polio vaccination is a routine
requirement for enrolling in public school in the U.S. In 1988, a set of international health organizations launched a global eradication program based on widespread vaccination—and the battle continues. As of January 2007, polio had been
beaten back to just four countries.
• Want to get warning of natural disasters?
Though we can’t yet predict earthquakes, science
does have effective ways of predicting when and
where hurricanes might strike land. Society has
put that knowledge to good use. The National
Weather Service continually collects data about
meteorological patterns and analyzes those data
based on our scientific understanding of weather
systems. They may then issue a hurricane warning, which gives citizens time to get to safety and
allows community organizers to prepare for evacuations and emergencies.
A satellite image of Hurricane Emily
approaching Mexico.
Polio vaccination photo provided by WHO/P. Virot; hurricane image from the National Climatic Data Center.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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• Want to repair our ozone layer? The ozone
layer shields us from damaging ultraviolet rays,
but in 1985, we discovered a chink in that armor—a hole in the ozone layer over Antarctica.
If things went unchecked, science predicted dire
outcomes: possible increases in DNA damage
and skin cancer rates, along with unpredictable
changes in the global food web caused by die-off
of UV-sensitive plankton. Luckily, science was also
ready with an explanation and a potential solution. The culprit seemed to be chlorofluorocarbons (CFCs), human-made chemicals used for air conditioning and aerosol propellants, which, chemists showed,
could destroy ozone molecules. Society took science to heart, and in 1990, policy
makers from 93 countries gathered in London to sign a treaty, agreeing to phaseout CFCs by 2000.
Science doesn’t tell us that we ought to prevent disease, provide advanced warning
in case of disaster, or protect our planet. People make those decisions based on their
own values, but once a decision is made, we can use scientific knowledge to figure out
how to accomplish that goal and what its likely ramifications will be.
Scientific knowledge informs public policies and regulations that promote our health,
safety, and environmental stewardship.
Find out how scientific research can shape public policy around the globe and help
protect the environment. Explore Ozone depletion: Uncovering the hidden hazard of
hairspray.
Visit the Visionlearning website for a case study on how scientific research influenced
regulations and policies regarding smoking.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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What science has done for you lately
In this section, we’ve seen that science touches many aspects of our lives: from the
mundane (e.g., the plastic lid on your morning coffee) to the world-changing (e.g., the
eradication of smallpox). And while some of the impacts of science on society may not
be clear boons, many are. Without science, we would not have even basic knowledge
about promoting health, safety, and environmental stewardship. This knowledge informs both our personal and societal decision-making. Scientific knowledge also forms
the basis for technological advancement. From a simple light bulb, to a complex computer, to genetically engineered rice—they are all man-made technologies based on
basic scientific knowledge.
Here, we’ve seen how scientific knowledge affects your life everyday, often without
much notice. But this doesn’t mean that you have to accept whatever scientific information the media throw your way. In the next section, you’ll learn how to become a
critical consumer of scientific information and how an understanding of science can
change the way you look at the world …
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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A scientific approach to life: A science
toolkit
Trans-fat free! Ethanol production: an eco-nightmare? Cancer researchers discover
new hope. Major petroleum company acknowledges reality of global warming. Clinically proven to reduce the appearance of wrinkles! These aren’t exactly the headlines
you’d find in a scientific journal, but they are examples of the sorts of scientific messages that one might encounter everyday. Because science is so critical to our lives,
we are regularly targeted by media messages about science in the form of advertising
or reporting from newspapers, magazines, the internet, TV, or radio. Similarly, as discussed in Science and society, our everyday lives are affected by all sorts of sciencerelated policies—from what additives are allowed (or required) to be mixed in with
gasoline, to where homes can be built, to how milk is processed. But you don’t have
to take these media messages and science policies at face value. Understanding the
nature of science can help you uncover the real meaning of media messages about
science and evaluate the science behind policies.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Untangling media messages and public
policies
Everyday, we are bombarded with messages based on science: the nightly
news reports on the health effects of
cholesterol in eggs, a shampoo advertisement claims that it has been scientifically proven to strengthen hair, or
the newspaper reports on the senate’s
vote to restrict carbon dioxide emissions
based on their impact on global warming. Media representations of science
and science-related policy are essential
for quickly communicating scientific
messages to the broad public; however,
some important parts of the scientific
message can easily get lost or garbled in
translation. Understanding the nature of
science can make you a better-informed
consumer of those messages and policies. It can help you:
• separate science from spin
• identify misrepresentations of science, and
• find trustworthy sources for further information.
To demonstrate how this works, we’ll look at a set of questions that you can use to get
to the science behind the hype:
As an example, we’ll apply these to a hypothetical article relating to global warming
that might have appeared in a major newspaper in the early 1990s …
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Ice cores offer clues to global warming question
An international group of researchers working in Tibet have recovered new clues
about Earth’s ancient climate. These clues come in the form of ice cores taken
from the Guliya ice cap, which are believed to contain information about the components of the atmosphere over the last 200,000 years.
The scientists are beginning analysis of one of the three cores recovered by the
expedition last summer. Lonnie G. Thompson, leader of the research team, said
that this core could reveal new insights about Earth’s climate through the last
four ice ages.
A better understanding of these climate patterns will inform the so-called “global
warming” debate.
Some scientists believe that human-produced carbon dioxide is causing Earth to
warm dangerously. This view is supported by some ice core studies. However,
skeptics question this opinion, arguing that we lack evidence that the warming is
not simply a natural part of the planet’s climate fluctuations.
Ice cores contain atmospheric “fossils”—bubbles of preserved gases and dust
from different times in Earth’s history. Thompson explained that “These long-term
archives will let us look at the natural variability of the climate over long periods
….”
Another ice core taken from Antarctica has suggested that carbon dioxide levels
and temperature have increased and decreased in sync over the past 160,000
years, rising to unprecedented levels today.
However, scientists have not yet come to a conclusion regarding the main question inspired by the ice core data: Do higher carbon dioxide levels actually cause
temperature increases?
To see how the article measures up against our set of tips, read on …
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Who dunnit: Where does the information
come from?
In paperback mysteries, the answer to this question is withheld until the last page …
… but when evaluating a media message about science, it’s one of the first things to
consider:
• What is the source of this message? Is it a sensational article in
Cosmopolitan, a report from the
New York Times, a feature in a
science publication aimed at the
general public like Discover, or
an original journal article? Each
of these sources will provide you
with a different level of information—and probably, a different level
of fidelity to the original science.
So if you are reading a short summary in your local newspaper, don’t
assume that you’ve got the whole
story!
• Does that source have an agenda or goal? All media messages have goals, which
can affect the information presented. For example, scientific messages that appear in advertising (e.g., “Clinically proven to reduce wrinkles”) are aimed at selling a product and are unlikely to give the full story. Some publications are aimed
at rallying readers around particular issues, like environmental activism, antienvironmentalism, or health issues, and so may present a skewed view of the science. If you really want the whole scoop on a scientific issue, it’s best to look for
a source whose main goal is to explain the science involved. Science publications
aimed at the general public provide this sort of information. As we’ve seen in other sections of this website, scientists strive to be unbiased in their scientific work,
but occasionally the media’s interpretation of this work introduces bias.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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An original piece of scientific research may be interpreted many times over before it
reaches you. First, the researchers will write up the research for a scientific journal
article, which may then be adapted into a simplified press release, which will be read
by reporters and translated yet again into a newspaper, magazine, or internet article—
and so on. Just as in a game of telephone, errors and exaggerations can sneak in with
each adaptation.
GETTING IT WRONG EVERY WHICH WAY
In 2004, an international group of researchers modeled the effect of predicted
climate change over the next 50 years, and reported that this amount of change
might eventually cause 15-37% of a select group of terrestrial species to go
extinct. It was simple, straightforward science. However, much of the press
coverage that followed was both sensational and inaccurate. For example, the
Guardian ran the headline:
An unnatural disaster:
• Global warming to kill off 1m species
• Scientists shocked by results of research
• 1 in 10 animals and plants extinct by 2050
In fact, most newspaper reports got it wrong, frequently suggesting that over a
million species would go extinct by 2050—and not, as the science implied, that
over a million species would be sentenced to extinction by 2050 and would actually die off afterwards. In addition, many websites picked up the story, and as
one might expect, conservation-oriented websites tended to run more sensationalized versions of the story, and websites with an anti-environmental bent tended
to dismiss the story. In this case, it’s clear that the media source of the story
made a big difference in the information offered to readers.
Our sample article on global warming seems to have been based on an interview with
a key scientist and possibly also a press release. However, no specific scientific publication (e.g., a journal article) is cited, which makes it difficult to learn more about this
work. On the plus side, we have no particular reason to believe that a major newspaper or the author would have any agenda other than to inform readers of an interesting development in science.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Beware of false balance: Are the views
of the scientific community accurately
portrayed?
Balanced reporting is generally
considered good journalism,
and balance does have its virtues. The public should be able
to get information on all sides
of an issue—but that doesn’t
mean that all sides of the issue
deserve equal weight. Science
works by carefully examining
the evidence supporting different hypotheses and building on
those that have the most support. Journalism and policies
that falsely grant all viewpoints
the same scientific legitimacy
effectively undo one of the main aims of science: to weigh the evidence.
Our sample article on global warming, for example, balances its report like this:
Some scientists believe that human-produced carbon dioxide is causing Earth to
warm dangerously. This view is supported by some ice core studies. However, skeptics question this opinion, arguing that we lack evidence that the warming is not
simply a natural part of the planet’s climate fluctuations.
and then ends it with more uncertainty:
However, scientists have not yet come to a conclusion regarding the main question
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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inspired by the ice core data: Do higher carbon dioxide levels actually cause temperature increases?
This report maintains journalistic standards for balance, but it’s not a very accurate
depiction of the state of science at the time. Even in the early 1990s, scientists who
studied the issue had weighed the evidence and concluded that global warming could
likely be traced to humanity’s increased production of greenhouse gases, like carbon
dioxide. Yet the newspaper article seems to give equal weight to the few skeptics.
And this false balance is not unusual. A survey of articles in topnotch U.S. newspapers
published between 1988 and 2002, found that 52.6% of those that dealt with global
warming balanced the human contribution to global warming with a skeptical viewpoint. Meanwhile, the scientific evidence for the human contribution to global warming became ever more convincing. A survey of 928 scientific journal articles published
between 1993 and 2003 found that none of them disagreed with the idea that human
activities are causing global warming! Such a disconnect between the true views of
the scientific community and those represented in the popular press make it difficult
for a casual reader to get an accurate picture of the science at stake.
WHO’S THE EXPERT?
Some popular science stories
provide journalistic balance by
including the views of two scientists—one on each side of an
issue. For example, a magazine
article about the origins of life
might quote Scientist A, who
argues that we have a good understanding of the chemical reactions that led up to the origin of
life, and Scientist B, who argues
that we don’t know much about
these reactions now and that we
never will. In untangling such
conflicting messages, it pays to
investigate each scientist’s area
of expertise. Knowing that Scientist A is a biochemist who studies
the origins of life and that Scientist B is a physicist who works on
electricity and magnetism could
factor into your assessment of
the controversy. Scientific knowledge is immensely deep and varies widely across fields. No single
scientist can be an expert on everything. Also, beware of science
stories that quote Dr. XYZ without explaining Dr. XYZ’s area of expertise. Plenty
of scientists don’t have Ph.D.s, and plenty of doctors (e.g., those with Ph.D.s in
English) don’t necessarily have a strong scientific background.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Too tentative: Is the scientific
community’s confidence in the ideas
accurately portrayed?
Contrary to popular opinion, science doesn’t prove a thing …
All scientific ideas—even the most widely-accepted and best-supported, like the germ
theory of disease or basic atomic physics—are inherently provisional, meaning that
science is always willing to revise these ideas if warranted by new evidence. However, that tentativeness doesn’t mean that scientific ideas are untrustworthy … and
this is where some media reports on science can mislead, mistaking provisionality for
untrustworthiness. For example, in our sample article, the evidence for humanity’s
contribution to global warming is depicted as shaky (“Some scientists believe that
human-produced carbon dioxide is causing Earth to warm dangerously. This view is
supported by some ice core studies.”), even though evidence supporting the idea is
actually quite strong. Sure, science can’t prove that human activities lead to global
warming, but neither can it prove the existence of gravity; yet both ideas are trustworthy and strongly supported by evidence.
Some policies make the same misinterpretation of provisionality in science. For example, in 2002, the U.S. government called for more studies to resolve “numerous
uncertainties [that] remain about global warming’s cause and effect” before taking
action. It is true that numerous uncertainties about global warming existed in 2002
and exist today. Uncertainty and tentativeness are inherent aspects of the nature of
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
9
science. However, even in 2002, climatologists had a strong and well-supported understanding of key features of global warming.
HEED THE HYPE
On the opposite end of the scale, some media reports blow the implications of scientific
findings out of proportion, failing to mention
caveats and additional research yet to be
done. For example, every few years, gene
therapy makes a spotlighted appearance in
the news—and for good reason. Gene therapy
holds the promise of correcting genetic diseases at their source by replacing broken
genes with working versions, but this is still
largely just a promise. A 1993 newspaper
article, for example, predicted that “Human
DNA will be a major heart ‘drug’ of the near
future with gene therapy a common treatment procedure,” though such treatment was
still unavailable as of 2007. Such sensationalized reports ignore the logistical difficulties
of getting new genes to the cells that need
them. So while the nightly news may herald widespread gene therapy as “just
around the corner,” a deeper investigation into the science behind the hype would
paint a different picture. Almost 30 years after the first rumblings about the possibility of gene therapy, the technique is still in experimental stages.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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What controversy: Is a controversy misrepresented or blown out of proportion?
Here’s a headline unlikely to
run in any paper: Senate getting along: No fights or arguments for days! That’s because
good news is generally no news.
Clashes, on the other hand, are
exciting and often important.
So it’s not surprising then that
media reports on science often
focus on controversy. However,
when a scientific idea is portrayed as controversial in the
popular media or in a policy,
that conflict might be one of a
few different types, which stem
from different sources:
• Fundamental scientific controversy—scientists disagreeing about a central hypothesis
or theory. If you imagine scientific knowledge
as a web of interconnected ideas, theories
and hypotheses are at the center of the web
and are connected to many, many other
ideas—so a controversy over one of these
principal ideas has the potential to shake up
the state of scientific knowledge. For example, physicists are currently in disagreement
over the basic validity of string theory, the set
of key ideas that have been billed as the next big leap forward in theoretical physics. This is a fundamental scientific controversy.
• Secondary scientific controversy—scientists disagreeing about a less central aspect
of a scientific idea. For example, evolutionary biologists have different views on the
importance of punctuated equilibrium (a pattern of evolutionary change, characterized by
rapid evolution interrupted by many years of
constancy). This controversy focuses on an
important aspect of the mode and rate of evolutionary change, but a change in scientists’
acceptance of punctuated equilibrium would
not shake evolutionary biology to its core. Scientists on both sides of the punctuated equilibrium issue accept the same basic tenets of evolutionary theory.
• Conflict over ethicality of methods—disagreement within the scientific community or
society at large over the appropriateness of
a method used for scientific research. For example, many people have concerns over the
ethicality of stem cell research that relies on
human embryonic stem cells. These cells are
gathered from fertilized eggs a few days old,
which are donated by couples undergoing in
vitro fertilization and who cannot use those
eggs. Such concerns do not represent conflict
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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over scientific knowledge, but over what constitutes ethical means for building
that knowledge.
• Conflict over applications—conflict over
the application of scientific knowledge. For
example, activists sometimes clash over the
issue of nuclear energy plants and whether
or not they are a safe and environmentally
sound means of producing energy. Although
there are honest scientific controversies on
issues relating to nuclear reactions, this is
not one of them. This is not a conflict over a
scientific idea, but over how such ideas should
be applied.
• Conflict between scientific idea and non-scientific viewpoint. For example,
scientific evidence supports the view that the Earth is about 4.5 billion years old;
however, some groups reject this view in favor of a young Earth, created just a
few thousand years ago. This is a conflict over scientific knowledge, but not one
within the scientific community.
True scientific controversy (the first two sorts listed above) is healthy and involves disagreements over how data should be interpreted, over which ideas are best supported
by the available evidence, and over which ideas are worth investigating further. This
sort of catalyst sparks careful examination of the data and additional research and so
can help science move forward. However, other sorts of controversy can impact science in different ways. Conflicts between scientific ideas and non-scientific viewpoints,
for example, can hinder science if the controversy shuts down research in contested
areas.
Furthermore, mistaking one form of controversy for another could easily lead one
astray about the science at stake. For example, our sample article on global warming refers to “the so-called ‘global warming’ debate,” but what is the nature of this
debate? As reflected by the reports from the Intergovernmental Panel on Climate
Change, the global scientific community is largely in agreement that global warming is occurring and that human activities are to blame—so this so-called debate is
not a fundamental scientific controversy. However, there are many smaller details of
climate change (how fast it is occurring, how best to model it, etc.) that are actively
being researched and discussed—so the debate is an example of a secondary scientific
controversy.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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COUNTERFEITING CONTROVERSY
The social controversy about
evolution has played out in
many ways, like this textbook
warning label, which was
ruled unconstitutional.
Evolution provides an example of a conflict between
a scientific idea and a nonscientific viewpoint. Biologists
overwhelmingly agree that
life has diversified through
evolutionary processes over
billions of years. Because
of this scientific consensus,
there is no fundamental scientific controversy over evolution. However, as with
any area of scientific research, secondary scientific controversies (in this case,
over the pace of evolutionary change, the frequency of different modes of speciation, etc.) continually arise as research progresses and scientists test new ideas
against evidence. Unfortunately, groups against teaching evolution in schools
sometimes take advantage of these secondary controversies, trumping them up
as fundamental controversies and falsely presenting them as indicators of a “theory in crisis.” Even more unfortunately, this misrepresentation has contributed to
a social controversy over what ideas should be taught in our science classrooms,
with the anti-evolutionists arguing for the inclusion of what they term alternative
viewpoints. This social debate has long since departed from the science at stake.
There is no scientifically viable alternative that can stand up to the overwhelming
evidence supporting evolutionary theory.
The four tips we’ve seen so far have all dealt with misrepresentations or exaggerations of science. To check out tips for evaluating the science itself, read on …
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Getting to the source: Where can I get
more information?
Sometimes an article in your
local newspaper just isn’t
enough. Maybe you’ve opened
your morning paper to a report
on herbal treatments for cold
symptoms. With your stuffy
nose and scratchy throat, the
idea sounds appealing—but you
need more information about
side effects, drug interactions,
and the supporting evidence.
Or perhaps you’ve heard about
policy changes that would encourage people to buy cars that
can run on ethanol instead of
regular gasoline, but before you jump on the bandwagon you want to know the scientific basis for this switch. A popular science article or an article in your local paper
may not give you enough information to make a judgment and may even selectively
discuss evidence, ignoring some lines entirely—but with a little extra research, you
can do better than your local paper. Where should you go to learn more about the science underlying these issues? For topics of current research, the books available at
your library may be out of date and many details are likely squirreled away in journal
articles that could be difficult to access and interpret. In this situation, the internet is
a great resource, but not all internet sites are created equal and not all of them offer
unbiased explanations of the science at stake.
Here are a few considerations for finding additional sources of scientific information
online:
• Find sources with scientific expertise. Try to find websites produced by a
research institute, a governmental body,
a respected educational institution, or
a major scientific association (e.g., the
American Psychological Association).
These sorts of organizations are all key
parts of the scientific community and have
an interest in accurately explaining scientific issues. For example, the Centers for
Disease Control, the American Association
for the Advancement of Science, the U.S.
Geological Survey, the U.S. Fish and Wildlife Service, or Nature magazine are all
trustworthy choices. On the other hand, Badger Creek Elementary and Tipsfromtodd.com probably don’t have access to up-to-date scientific information and may
not feel any responsibility to provide fair and accurate information.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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• Avoid ulterior motives. Try to
avoid websites from groups that
might stand to gain by biasing the
information presented, like some
lobbying or advocacy groups. It’s
particularly important (and easy)
to avoid websites that are trying to
sell something. For example, Buyherbal.com is unlikely to give unbiased evidence of the effectiveness
of the herb Echinacea. Instead you
might try the National Institutes
of Health website, since that organization has no stake in the issue
other than helping people stay informed and healthy.
Can you spot the conflict of interest?
• Keep it current. Science is ongoing and is continually updating and expanding
our knowledge of the universe. Scientists publish many hundreds of papers each
year on areas of active scientific research. For example, in 2006 alone, more than
15,000 scientific articles on the topic of breast cancer were published. Because
of the rapid pace at which our scientific knowledge advances, websites can easily
become out-of-date if not actively maintained. So a website last updated in 2002
is unlikely to give you a useful understanding of the costs and benefits of using
ethanol as fuel. Instead, look for a more current website.
• Check for citations. As described in Scientific culture, scientific publications
generally give credit to related research by providing a list of citations—and that
means that citations can help you gauge a website’s scientific validity. A website that provides a comprehensive list of citations from scientific journal articles
is more likely to provide an accurate portrayal of the science involved than one
with suspicious, scanty, or nonexistent references. As an added bonus, by studying those references, you can double-check the website’s information or dig even
deeper into the issue.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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As an example of how one might get more information on a science-related issue, let’s
return to our sample article on global warming, which briefly describes scientist Lonnie Thompson’s ice core studies. Where could one find more details on ice cores and
how they can inform global warming research? First, you might check out an interview with the scientist from National Geographic. This 2004 article is written for the
general public (and includes no citations) but is from a trustworthy source and offers
the direct perspective of a scientist involved with the work. And if that’s not enough,
you might turn to NASA’s in-depth tutorial on paleoclimatology, which meets all of our
guidelines: it’s from a trustworthy source without ulterior motives (NASA), was posted
relatively recently (2005), and includes citations from the scientific literature.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Convince me: How strong is the evidence?
When evaluating a scientific idea, scientists carefully consider the relevant evidence …
… and you can too. You’ve read an article in the newspaper, done a little more research, uncovered several lines of evidence, and now it’s time to weigh those data for
yourself. Here are some questions to ask as you consider the evidence:
• Does the evidence suggest correlation or
causation? In other words, do the data
suggest that two factors (e.g., high blood
pressure and heart attack rates) are correlated with one another or that changes
in one actually cause changes in the
other?
• Is the evidence based on a large sample
of observations (e.g., 10,000 patients with
high blood pressure) or just a few isolated
incidents?
• Does the evidence back up all the claims
made in the article (e.g., about the cause
of heart attacks, a new blood pressure
drug, and preventative strategies) or just
a few of them?
• Are the claims in the article supported by
multiple lines of evidence (e.g., from clinical trials, epidemiological studies, and
animal studies)?
• Does the scientific community find the evidence convincing?
For example, our sample article on global warming mentions one relevant line of evidence—ice cores—but provides few details. A little additional research reveals that
ice cores contain bubbles of air captured from Earth’s atmosphere many hundreds of
thousands of years ago. Those air bubbles contain isotopes of oxygen that provide
an indication of past temperatures. These samples suggest that, historically, global
temperatures have risen and fallen in step with carbon dioxide levels. And further research into global warming uncovers other lines of evidence—for example: modern
atmospheric records indicate that human activities have been increasing the concentrations of carbon dioxide and other greenhouse gases in the atmosphere, modern climate records indicate that the climate is currently warming, and models of the Earth’s
atmosphere provide a picture of why increased carbon dioxide levels might lead to
higher temperatures. The scientific community finds this evidence convincing.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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FOLLOW THE MONEY
When examining the evidence behind a scientific issue, it’s worth paying attention
to the funding source for that research. Is it a group with no particular stake in
the outcome (like the National Science Foundation), or is it a group with a more
personal interest in the issue? Mars Incorporated, for example, funds research on
the benefits of chocolate, and tobacco companies have funded research on the
health effects of smoking. If research is funded by an interested party, it makes
sense to examine that study carefully. Do its findings fit with those of other studies? Does the study seem to be fairly designed? Scientists strive to design fair
tests and assess the evidence without bias, but because scientists are human
too, biases sometimes sneak in and can take time to be corrected. For example,
several studies have found that research funded by pharmaceutical companies is
more likely to produce results favoring the company’s product than is research
with other funding sources.
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org
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Summing up the science toolkit
Here, we’ve seen that a little consideration can go a
long way towards assessing the scientific messages
that come your way everyday—whether it’s the hearthealthy logo on your cereal box or a news report of a
government decision on coastal conservation. You can
get to the science beneath the spin by applying what
you know about how science works: how scientific
ideas are evaluated and publicized, the inherent provisionality of scientific ideas, the nature of scientific
controversy, and how science is funded. Science itself
is simply a way of learning about the natural world,
but because that knowledge is powerful and affects
many aspects of our lives, identifying misinterpretations and misrepresentations of science is a key part
of a scientific outlook on life.
But that’s not all that a scientific view of the world
will buy you. Some aspects of the process of science
can be put to use in your everyday life. For example,
you can use scientific reasoning, evidence, and ideas
to solve everyday problems—like figuring out what’s
wrong with your car by testing one hypothesis about
the problem at a time, just as a scientist might set up
an experiment. More generally, a scientific view of the
world can help you retain and increase your curiosity
about and appreciation of the natural world. A view of
the Himalayas is certainly breathtaking, but it is even
more powerful when viewed with an understanding of
the natural processes that the mountain range represents—40 million years of colliding plates pushing up
peaks and exposing them to the slow work of erosion.
The night sky is pretty, but it is fascinating when one
understands the distance of the stars and the ancient
events that their light represents. And a hummingbird
is beautiful, but it is awe-inspiring when one considers
the lightning rate of the chemical reactions within its
cells that power its fast-beating heart. Science asks
the deepest of all questions about the natural world
around us: how did the universe get to be the way it
is today, and what will it be like tomorrow? This is an
incredible mystery—but one which science gives us
the tools to understand and appreciate.
A scientific view of the world has
many practical benefits and can also
help you to better appreciate the
natural world.
Fire weather map provided by National Oceanic and Atmospheric Administration’s National Weather Service; nutrition facts
image provided by U.S. Department of Health and Human Services; medicine bottles provided by Courtesy Dewitt Stetten,
Jr., Museum of Medical Research, National Institutes of Health; hummingbird photo provided by Dr. Lloyd Glenn Ingles ©
California Academy of Sciences; Himalayas photo provided by NASA; star photos provided by NASA/ ESA/Antonella Nota
(STScI/ESA).
© 2013 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California • www.understandingscience.org