Scientific Method
Beginnings
• Aristotle (384 BCE-322 BCE or BC)
• ancient Greek philosopher
Aristotle
• Aristotle, more than any other thinker, determined
the orientation and the content of Western
intellectual history. He was the author of a
philosophical and scientific system that through
the centuries became the support and vehicle for
both medieval Christian and Islamic scholastic
thought: until the end of the 17th century, Western
culture was Aristotelian. And, even after the
intellectual revolutions of centuries to follow,
Aristotelian concepts and ideas remained
embedded in Western thinking.
• In other words, Aristotle was so
famous that his work influenced
thinking in the Western world from
his time to the present.
• This was fine when he was right. But
he was so influential that his
mistakes were never noticed.
• Aristotle and his contemporaries
believed that all problems could be
solved by thinking about them.
• Sometimes this worked, other times
it did not.
• For example, Aristotle thought that
heavy objects would fall faster than
lighter ones.
• Now that does seem reasonable at
first. And this is how “science” was
done in ancient times.
• But what did Aristotle not do?
• He never tested his ideas!
• The world would have to wait almost
2000 years for that to happen.
Galileo Galilei
•1564-1642 AD or CE
•Lived in what is today
Italy
•Is considered to be
the first true scientist.
•Why????
•Because he actually did
the experiment.
• Aristotle said that heavy objects fall
faster than lighter ones.
• So Galileo asked, “How much faster?”
• So he sent students up to the top of
a building and had them drop a heavy
ball and a lighter one off at the same
time. He had other students waiting
below to measure the difference in
time between the two hitting the
ground.
• Today of course we know what happened.
Much to everyone’s surprise both balls hit
the ground at about the same time!
• This shows that it is much preferred to
test your ideas rather than merely think
about them.
• One test is worth a thousand expert
opinions. Bill Nye
Key Idea
• When conducting an experiment,
change one factor and keep
everything else exactly the same.
• The one thing you change is called the
variable.
• All the things you keep the same are
called controls.
Galileo’s Experiment
• What was the variable in Galileo’s
experiment?
• The weight of the balls.
• What were some controls?
• Dropped from same height.
• Dropped at same time.
• Balls had same shape/size.
Review
Variable: the
one thing you
change in an
experiment.
Manipulated
variable: you
change this
yourself.
Independent
variable: on its
own.
Data: the
information you
get when you
test the
variable.
Responding
variable:
responds to the
change you
made.
Dependant
variable:
depends on the
change you
made.
Controls: the
parts of the
experiment that
stay the same.
Controlling
variables
Controlling
variables
Scientific Method Steps
•
•
•
•
•
•
State the problem.
Make a hypothesis.
Conduct the experiment.
Record/analyze data.
Make a conclusion.
Report findings to others so they can
repeat the experiment.
Hypothesis
•
•
•
•
An educated guess
a prediction
Use “If”, “then” format
We predict that if we drop a ball
from a higher height, then it will
bounce higher.
• “If” is the manipulated variable.
• “Then” is the responding variable.
Observations
• Observations: We use our senses to
gather information about the world
around us. There are two types of
observations.
Qualitative
• Qualitative observation: (quality)
Usually made with our senses.
• Color, shape, feel, taste, sound.
• Olivia is wearing a blue sweater.
• The lab tabletop is smooth.
• The dog’s fur is shiny.
Quantitative
• Quantitative observation: (quantity)
How many. Will always have a number.
• Based on exact measurement.
• The room is 8 meters across.
• Sarah is 141-cm tall.
• Sam weighs 450
Newtons.
Inferences
• Inference:
• A logical interpretation of an event
that is based on observations and
prior knowledge.
• What does this mean in 6th grade
terms?
Making Inferences
• You are at the counter in the office to get a
bus pass signed. You see a student leave the
principal’s office crying and upset. We could
make an inference as to why the student is
upset.
• Could be in trouble (ISS, OSS, expelled)
• Family problems at home (sick, accident)
• Student not feeling well
• Student has poor grades (failing, retention)
Theory
• Has a very different meaning in
science than in everyday life.
• “The detective has a theory about
who robbed the bank.” This is a
guess.
• When scientists use the word theory
it is not used as a guess.
Theory defined
• An explanation based on many
observations during repeated
experiments that is valid only if it is
consistent with observations, makes
predictions that can be tested, and is
the simplest explanation.
• A logical, time tested explanation for
events that occur in nature.
• So the theory of gravity, theory of
electricity, the germ theory of disease,
and the theory of evolution are tested,
accepted explanations for events that
occur in nature.
• Theories can really never be completely
proven, only disproven. When new evidence
comes along, we must modify our theory or
at times even get rid of it and start over
again.
• Ptolemy’s earth centered theory of
the solar system is an example of
what can happen when new evidence
comes along. When Copernicus
showed that putting the Sun in the
center made it much easier to predict
the planets motions, the old earth
centered theory was discarded and a
new one developed.
Graphing
• Graphs are a useful tool in science.
• The visual characteristics of a graph make
trends in data easy to see.
• One of the most valuable uses for graphs is
to "predict" data that is not measured on the
graph.
Graphing Steps
•
•
•
•
Identify the Variables
Determine the range
Determine the scale
Number and label each
axis
• Plot the points
• Draw the graph
• Give your graph a title
Identify the Variables
– Independent Variable (the thing you changed)
 Goes on the X axis (horizontal)
 Should be on the left side of a data
table.
– Dependent Variable (changes with the independent variable)
 Goes on the Y axis (vertical)
 Should be on the right side of a data
table.
Range
– Subtract the lowest data value from the
highest data value.
– Do each variable separately.
Scale
– Determine a scale,
(the numerical value for each square),
that best fits the range of each variable.
– Spread the graph to use MOST of the
available space.
Label Axis's
• You need to tell everyone reading your
graph what the graph means.
• Be sure to include units.
Plotting
• Plot each data value on the graph with a dot.
You can put the data number by the dot, if it
does not clutter your graph.
Drawing
– Draw a curve or a line that best
fits the data points.
– Most graphs of experimental data
are not drawn as "connect-thedots".
Title
• Your title should clearly tell what the graph
is about.
• If your graph has more than one set of data,
provide a "key" to identify the different
lines
• While your high school teachers might not
like it, I do like putting your name in the
title of the graph.
• Rachel and Max’s Sunspot Graph
Interpolation
• Interpolate:
predicting data
between two measured
points on the graph.
Extrapolation
• Extrapolate:
extending the graph,
along the same slope,
above or below
measured data.
Operational Definition
• A very clear and very precise
explanation of the items
being measured.
•
A method to ensure that
anyone making the
measurement will get the
same answer.
• Basically you are deciding
how each variable is being
measured.
How will we measure?
• In the Bouncing Ball Lab
we are measuring how
high the ball bounces
when dropped.
• But where do we measure
to?
• The bottom. Top, or
middle of the ball?
• It makes a difference.
Our Definition
• We will all measure
from the floor to the
bottom of the ball.
• This way we will get
consistent results.