Evolution of Scientific
Reasoning
A Very Brief Study
Before there was science…
Prior to the introduction of “science” and
“scientific reasoning,” people believed that
gods
control
everything…
Thales
600 BCE
Said all nature is made
of water
Rational explanation for
physical phenomena.
Ex: Earthquakes: earth
floats on water and the
motion of the water
causes the earth to
shake!
Other Cool Things Thales Did…
• Used geometry to
measure the
pyramids, calculate
ships’ distance from
shore
• Predicted a solar
eclipse 585 BCE
• Asked “What is the
nature of matter?”
Pythagoras
500 BCE
Said our world is ruled
by numbers
Math and physics still
use his theorem. Do
you know it?
Socrates
400 BCE
First to say that no
gods are involved in
nature, just logic and
rules.
More Fun Facts about Socrates
• Believed
knowledge was the
true path to
goodness.
• Accused of
corrupting the
youth and “not
believing in the
gods of the state,”
and was sentenced
to death.
Plato
350 BCE
First to come up with
the theory that “Forms”
or ideas organize
matter so that we can
understand it.
He was Socrates‘s
student!
Aristotle
370 BCE
Studied biology, physics
and anatomy using
observation and
reasoning.
He was Plato’s student!
What You Never Knew about
Aristotle
Aristotle became a
great teacher.
One of his students was
Alexander the Great.
Alexander the Great is
Mrs. Macomber’s
great-great-greatgreat-great-great…
grandfather
So don’t make her
angry…
Now back to science…
Late Grandpa Alex
Then There Were None
• Shortly after Grandpa Alexander’s death
and the burning of the Library at
Alexandria, the world entered into the
Dark Ages
• No science was being done, no progress was
being made. In fact, science was considered
sorcery and that was no bueno.
Glimmer of Hope
• The Middle East did not enter this
science-less abyss like Europe did.
• In fact, it is the Muslim scientists that are
thought to be the founders of modern
Chemistry.
• And that’s where we find this guy…
Jabir ibn Hayyan
770 AD
First practicing alchemist
Knew that the properties
of metals could be
rearranged to make
different kinds of
metals.
Fun Facts on Jabir ibn Hayyan
• Alchemical
investigations
revolved around the
goal of producing
artificial life.
• Designed and used
20 types of nowcommon lab
equipment.
Meanwhile back at the Ranch…
-- 1348 AD: Europe suffers through the
Bubonic Plague
A few [hundred] short years later, they’ve
recovered and they’re ready to get down
to business!
Welcome Home, Science!
SCIENTIFIC REVOLUTION!!
Art, science, and math are back at the top!
Galileo Galilei
1600 AD
Father of Modern
Science
Said that all of the laws
of nature are
mathematical
The Life and Times of Galilei
Charged as a heretic by
the Church for
heliocentric (Suncentered) model of the
solar system
Constructed the
thermometer.
Isaac Newton
1700 AD
Brought back
“Hypothesis” to the
scientific process
Did some important stuff
with math and
physics, too, I think…
And So It Goes
--1937: First placebo trials take place to
introduce control groups
--1946: First computer simulation
“Adam”
2009 AD
First “Robot Scientist”
Makes hypotheses,
conducts experiments,
draws conclusions with
no human involvement.
Which Brings Us To…
SCIENTIFIC METHOD!
It’s a way to ask and answer scientific
questions by making observations and
doing experiments.
What do you want to learn?
What problem do you want to
solve?
What is already known about this
topic?
Hypothesis – an educated guess
If this, then that.
Follow a step by step procedure.
Must be repeatable.
Data: charts or graphs
Observations: write about what you
see
Conclusion: a written summary to
communicate results
Must include WHY your hypothesis
was right or wrong.
Was there a mistake or error? Does the
experiment need to be repeated?
Experiment Design
• Let’s talk variables!
• Variables are things that can change
during an experiment. There are 3 main
types…
Independent Variable
• Independent Variable: the one thing you
change in an experiment. This is what
you’re testing.
• A good experiment has ONLY one
independent variable at a time.
Uh, what?
• I watched Idiocracy and they watered their
plants with Brawndo: The Thirst Mutilator. That
failed miserably for them, but it got me
thinking…
• Question: Is there another liquid that
would make plants grow better than
water?
• Hypothesis: If orange juice is used
instead of water, then a plant will grow
taller.
OJ vs H2O, Round 1
• Experiment Design: Variables:
• I have decided to test which liquid makes
plants grow taller.
• So my independent variable, the thing I’m
testing, the thing I’m changing from plant
to plant is…..
right, the liquid.
Dependent Variable
• Dependent Variable: the change that
happens because of the independent
variable
• This is what you measure.
Back to the Juice
• If I give one plant water and one plant
orange juice, what result am I going to be
measuring?
• In my experiment, plant height is what I
measure, and this is my dependent
variable.
Last Variable
• Controlled Variable: Everything that you
want to remain constant and unchanged.
• Remember good experiments only test
one thing at a time. Everything else is a
“control.”
My Poor Plants
• So while I’m juicing up my plants, here are
some thing I’ll make sure to keep the
same between plants:
•
•
•
•
•
•
The same kind of plant
The same kind of soil
The same location
The same amount of light and heat
The same volume of liquid
I’ll “water” them at the same time.
What else can you add??
Your Turn!
• I’m going to give your group a question.
• Come up with a hypothesis.
• Define independent and dependent
variables.
• Come up with at least 10 controlled
variables for your experiment.
Last Little Bit
• There are 2 main ways that independent
and dependent variables are related to
each other.
– Directly Proportional
– Inversely Proportional
When We Graph This Stuff
Directly Proportional
• As the independent variable increases, the
dependent variable increases.
What are some other examples of things
that are directly proportional??
Inversely Proportional
• As the independent variable increases, the
dependent variable decreases.
What are some other examples of things
that are inversely proportional??
Review
• Here are some questions about Scientific
Method and scientific reasoning pilled from
EOC Review.
• So on May 4th, you will see things like
this…
What I change =
independent
Always 50g =
control
• A student sets up an experiment to investigate
the effect of temperature on the volume of 50g
of gas inside a balloon. Which statement
correctly describes the design of the
What I’m testing =
experiment?
dependent
a. The temperature is an experimental control, and the
volume is the independent variable.
b. The volume is an experimental control and the
temperature is the dependent variable.
c. The mass of the gas is an experimental control, and
the temperature is the independent variable.
d. The temperature is an experimental control, and the
mass of the gas is the dependent variable.
•
Scientist Henri Becquerel observed that
some minerals, such as potassium uranyl
sulfate, could release energy when placed on
a photographic plate wrapped in black paper.
Becquerel concluded that the potassium
uranyl sulfate absorbed energy from the sun
and then released energy to expose the
photographic plate. Later Becquerel
proposed an alternate explanation for the
same experiment: the uranium in potassium
uranyl sulfate released energy without energy
being absorbed from external sources.
• Which statement best explains why
Becquerel’s later explanation was more
likely to be accurate?
a. Becquerel was considered the best scientific thinker
of his time. Even the best ones are wrong sometimes.
b. Becquerel’s peers reasoned that his explanation
was scientifically sound.Doesn’t matter what other people think.
c. Experiments showed that a sample of uranium could
expose a photographic plate even if it was kept in
the dark.
d. Scientists were unable to determine the mechanism
by which uranium could absorb and release solar
energy. That can’t prove or disprove anything…
• Two measuring tools are shown.
• Which is the most appropriate for
measuring 30.0mL of a sodium chloride
solution?
a. The beaker because it is more stable and the
liquid is less likely to spill. That’s why we’re careful in lab.
b. The beaker because it is calibrated to hold
large amounts of liquid. Doesn’t matter how much it will hold.
c. The graduated cylinder because it is calibrated
to measure the liquid more precisely.
We need it to be CORRECT!!
d. The graduated cylinder because it will be nearly
Doesn’t matter how much it will hold.
filled with liquid.
•
A company wanted to begin
manufacturing and promoting floor
cleaner that it claimed would clean
floors better than previous products.
The company sent its product to two
independent research groups, which
determined the floor cleaner did clean
floors better than previous products.
How did the research company come
to a bias-free conclusion?
a. Each test was repeated multiple times until the
desired results were obtained. BAD science!!
b. Both research groups came to the same
conclusion when reviewing the company’s
claim. Knowing what it should be affects how hard you try to be “right.”
c. Both research groups used standard protocols
made available for the tests. What you’re supposed to do…
d. Technicians at each research group did not
know which products they were testing and
comparing. Can’t cheat if you don’t know which one you have!!
• Scientists built a prototype of an electric
device that may help predict human
reactions to new medicines. Which next
step should the scientists take to determine
whether the device will be useful?
a. Test the device
Yes, let’s make sure it works
b. Modify the device
Should see how it works first…
c. Reevaluate the design of the device
Should see how it works first…
d. Build the real device for application
Should make sure it works first…
• Air pollution from automobile exhaust is
minimized by using electric cars powered by
lead-acid batteries. What will be the negative
effect of using lead-acid batteries?
a. Toxic metal in the batteries will enter the
environment. Toxic is bad. Very bad.
b. Sulfuric acid in the batteries will generate
electricity. Electricity is good…
c. Oxygen and hydrogen will be produced by the
batteries. Not bad for the environment…
d. Dense and malleable metal will be used in the
batteries. So is gold, and no one complains about that…
The End
• Next time we’re going to discuss data!
– Charts, graphs, observations, etc.
• “Lab” Wed/Thurs. The only one ever
where you can wear shorts!