Scientific Method
Beginnings
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Aristotle (384 BCE-322 BCE or BC)
ancient Greek philosopher
VERY INFLUENTIAL
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
Scientific Method Steps
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Observe the natural world around you
- observations and inferences
State the problem.
Research and gather information
Make/Form a hypothesis.
Test the hypothesis
a. Conduct the experiment.
b. Build a model
Record/analyze data.
Make/draw a conclusion.
a. Report findings to others so they can repeat the experiment.
b. Modify hypothesis
Observe the Natural World
Around You
• Observations: We use our senses to
gather information about the world
around us. There are two types of
observations.
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.
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.
Inferences
• Inference:
• A logical interpretation of an event
that is based on observations and
prior knowledge.
• What does this mean in 9th 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)
Research and Gather
Information
• Learn as much as possible about the
background of the problem.
- Have others found information that will
help you determine the tests to do and
which tests will be helpful?
State the Problem
Why does it happen?
How does it happen?
Form/State a Hypothesis
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An educated guess
a prediction
Use “If”, “then” format
“If” is the independent variable or the
manipulated variable.
• “Then” is the dependent or responding
variable.
• Example:
We predict that if we drop a ball from a
higher height, then it will bounce higher.
Testing a Hypothesis
• Experiment, Experiment, Experiment!
• Build a Model
Key Idea
• When conducting an experiment, change
one factor and keep everything else
exactly the same.
• The one thing you change is called the
independent variable.
• All the things you keep the same are called
constants.
• A control is the standard by which the test
results can be compared. It does not
receive the independent variable!
Galileo’s Experiment
1. What was the independent variable in
Galileo’s experiment?
• The weight of the balls.
2. What was the dependent variable?
• The time it took to fall to the ground.
3. What were some constants?
• Dropped from same height.
• Dropped at same time.
• Balls had same shape/size.