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The Scientific MethodThe Scientific Method
Pushing back the frontiers of human knowledge.
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GoalsGoals
• What is science?• What is the scientific method?• Does the scientific method work?• What is not a scientific argument.• Why are you here?
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What is science?
• You see something happen, you ask why?
• You want to make something happen, you ask how?
• Science is a tool for answering why and how.
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Science as a tool
• Medicine:“I have high cholesterol, what should I do?”– Take cholesterol lowering medication.– Consult my astrologer.– Pray to the god Baal and sacrifice a goat.
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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!
• A scientific theory must do two things:– Explain what is seen.– Predict what will happen in the future.
• Implicit predictions• Explicit predictions
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The Scientific Method
1. Observe an event.2. Develop a model (or hypothesis) which
makes a prediction.3. Test the prediction.4. Observe the result.5. Revise the hypothesis.6. Repeat as needed.7. A successful hypothesis becomes a
Scientific Theory.
model
test
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Medical ScienceScientific 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? Re-run medical test. Observe results.
Scientific Theory
Lipitor reduces cholesterol.
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Everyday Science
Scientific Method Making Spaghetti Sauce
Observation Spaghetti sauce should be red.
Hypothesis (prediction)
Maybe try a tomato sauce.
Test Heat pot of tomato sauce.
Observe result Taste the sauce - bland.
Revise hypothesis? Use tomato sauce and garlic!
New test? Add garlic, taste - not so bland.
Scientific Theory The Final Recipe.
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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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Theories
• 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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Concept Question
• Which of these statements is NOT true.“A scientific theory:
a. is a hypothesis that has been proven correct.”b. can be proven false.”c. is only true as long as it is supported by the
results of new experiments.”d. predicts new phenomena and ties together a
variety of observations.”e. tells you what experiments will disprove it.”
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Concept Test
• Which of the following DO NOT satisfy the requirements of a scientific theory?
a. In the absence of an outside energy source, the amount of disorder in a system increases with time.
b. In the case of a very high mass in very small volume, there is a distance from the center inside of which no information reaches us on the outside.
c. The better a species is adapted to its environment the more likely it is to pass on the ability to survive to its descendents.
d. The conditions necessary for life to have arisen on Earth are too complex to have occurred by chance.
e. The making of leavened bread requires yeast.
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Textbook vs. Newspaper Theories
• “Textbook” Theory:– Well established (decades to centuries)
Sun centered solar systemTheory of gravity
• “Newspaper” Theory:– Tentative to strong support
String TheoryDark matter
• Often mixed together in media and minds
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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
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Concept Test
• Consider the following theory. Why does it not satisfy the requirements of a scientific theory?
“The chain of events needed for life to arise is too complicated to have happened by chance, a divine intelligence must therefore have caused life to arise (Intelligent Design).”
a. It contradicts the theory of evolution.b. It makes no prediction which can be tested.c. It assumes there is something we don’t understand.d. It assumes there is a God.e. It doesn’t rely upon any observations.
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Limits to Science
• What limits the questions science can answer?
• What types of questions can science not answer?
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Homework #2Homework #2
• Due Friday 10-Sept: Read Ty12 and Sagan article 1 (Sg1): Science and Hope from Demon Haunted World.
• Why is belief in science not just a replacement for belief in astrology or religion?
• One should be skeptical of astrology because:a. It takes power out of the hands of scientists.b. It can’t be tested.c. It has failed when tested.d. It proposes forces that are non-physical.e. It threatens our belief in a knowable universe.
