The Scientific Method
Pushing back the frontiers of human knowledge.
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Science as a tool
• Science is a tool for answering why and how.
• “I have high cholesterol, what should I do?”
– Take cholesterol lowering medication.
– Consult my astrologer.
– Pray to the god Baal and sacrifice a goat.
• How do you choose what to do?
• What is your criteria for the “best” solution?
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Tyson Episode 1
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Test ideas by experiment and observation.
Build on those ideas that pass the test.
Reject those ideas that fail the test.
Follow the evidence wherever it leads.
Question everything.
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The Scientific Method
1. Observe an event.
2. Develop a model (or hypothesis) which makes a
prediction.
model
3. Test the prediction.
4. Observe the result.
5. Revise the hypothesis.
test
6. Repeat as needed.
7. A successful hypothesis becomes a Scientific
Theory.
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Medical Science
Scientific Method
High Cholesterol
Observation
Patient has high cholesterol
Hypothesis
(prediction)
Certain chemicals may dissolve
cholesterol deposits.
Test
Give 100 patients these chemicals,
give 100 patients placebo.
Observe result
Same number lower their
cholesterol as placebo patients.
Revise hypothesis? Try different combo of chemicals.
New test?
Scientific Theory
Re-run medical test. Observe
results.
Lipitor reduces cholesterol.
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Recap: Theories, Guesses, Laws
• What does the word “Theory” mean to you?
“A conjecture; guess” (Webster’s Dictionary)
• Does it mean the same to a scientist?
“A model which has been born out by repeated
tests and observation.”
• Is a Theory less than a Law?
“Evolution is just a theory, it is not a fact.”
• Do Theories “grow up” to be Laws?
“Einstein’s Theory of Relativity”
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Concept Question
• Which of these statements is true.
a. A theory becomes a Law after it has been proven
correct.
b. A theory becomes a Law if it is supported by the results
of enough experiments.
c. A Law that is refuted by experimental results becomes
just a theory.
d. The movement of the Earth around the Sun and the
formation of the Universe in the Big Bang are theories.
e. We should withhold judgments on theories until they
become Laws.
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Limitations of Science
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Key to the scientific method is The Test.
Q: What can and cannot be tested?
Q: What is and is not reproducible?
A: Magic, the Divine, matters of faith cannot be
tested and are not reproducible.
• Result:
1. Science is the search for natural or material explanations to
the Universe.
2. Science is limited to those questions of which natural or
material explanations can be applied.
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Assumptions of Science
• To what questions are natural or material
explanations applicable?
– God of the Gaps
– The unknown versus the unknowable!
• Are we justified in assuming that natural or material
explanations are sufficient to describe the world?
– Personal Experience
• The Universe isn’t random.
– The same test done by you, me, yesterday and tomorrow
should all give the same result.
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Theories
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So: a theory is a highly successful hypothesis.
All hypotheses make predictions.
All theories make predictions.
All theories can be tested.
Result: Any scientific theory is subject to
change as our ability to make tests, or make
observations of a test’s results, improves with
time.
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Non-scientific Theories
• Make no predictions
• Un-testable
• Can’t be falsified
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Non-scientific Theories
• Cholesterol too high?  Aliens are clogging
your arteries with invisible probes.
• Spaghetti is bland?  You were meant to eat
bland food.
• Cholesterol too high?  Gods must be angry.
• Spaghetti is bland?  At the instant of
tasting, tongue is transported to alternate
dimension where all flavors are rendered
nullified. Happens instantaneously.
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Non-scientific Theories
Viking Orbiter (1976)
Mars Global Surveyor (1998)
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Falsification
• A real Scientific Theory tells you what
observations are necessary to falsify it.
– Not so proponents of:
• Face on Mars
• Moon Hoax
• Astrologers
• Intelligent Design
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Question of Belief
• Which of the following do you believe?
1. God created human beings and all forms of life
in their present form at some point in the past.
2. Humans have evolved from earlier forms
through a process guided by God or some other
Intelligence.
3. Humans have evolved from earlier forms of life
through a process of natural selection and
random mutation.
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Evolution & Public
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Tests and Theories
• Science is a tool for telling you what works!
• How do you know if your theory (idea,
model, hypothesis) is right?
– You can test it!
– I make a claim, you can test that too.
• A scientific theory must do two things:
– Explain what is seen.
– Predict what will happen in the future.
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Predictions
• The Theory of Evolution makes testable
predictions and thus is a successful scientific
theory.
1. True
2. False
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Predictions
• Intelligent Design says that human beings
(and life in general) is too complex to have
arisen naturally and therefore must have been
created. Does this statement make testable
predictions?
1. Yes
2. No
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