2 The Scientific Method Pushing back the frontiers of human knowledge.

2 Goals What is science? What is the scientific method? Does the scientific method work? What does the scientific method assume? What is not a scientific argument.

2 Science as a tool Science is a tool for answering why and how. “I have high cholesterol, how can I lower it?” –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?

2 Tests and Theories Science is a tool for telling you what things work! How do you know if your theory (idea, model, explanation, hypothesis) is right? You can test it!

2 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

2 Concept Test What must a scientific theory do? a.Explain what is seen and successfully predict the results of future experiments. b.Explain the results of previous observations and tie together a wide range of ideas. c.Be based on data and unify disjointed sets of ideas. d.Predict the results of future experiments and be falsifiable. e.All of the above.

2 Daily Life Give an example from your daily life of an instance when you used the scientific method? Write down what your theory is. –Be sure your final theory satisfies the requirements of a scientific theory.

2 Everyday Science Scientific MethodMaking Spaghetti Sauce ObservationSpaghetti sauce should be red. Hypothesis (prediction)Maybe try tomato sauce. TestHeat pot of tomato sauce and taste. ResultThe sauce is bland. Revise hypothesis?Use tomato sauce and garlic! New test?Add garlic, taste - excellent. Scientific TheoryThe Final Recipe.

2 A Theory’s Power A successful theory means: –Uses your previous knowledge and experience. –Applies to the future (the prediction) –You don’t have to keep doing the test. Example: –Recipe: No more trial and error –Can move on to more sophisticated recipes. Do your daily examples satisfy this requirement?

2 Reproducibility Anyone must be able to reproduce the claims of your result. –Cookbooks (In)Famous examples: –Cold Fusion –“Wow!” SETI signal The conservative nature of Science.

2 Concept Test Which of the following is a weakness of the scientific method? a.A scientific theory is considered correct only as long as the results of new experiments continue to confirm it. b.A scientific theory that has been widely accepted can still be called into question by the results of single new experiment. c.If one researcher claims a result that can not be reproduced by another researcher, then the first researcher’s results may not be believed. d.All of the above. e.None of the above.

2 Textbook vs. Newspaper Theories “Textbook” Theory: –Well reproduced (decades to centuries) Sun centered solar system Theory of gravity “Newspaper” Theory: –Tentative to moderate support (possibly reproduced) String Theory Dark Matter Dark Energy Often mixed together in media and public minds

2 Concept Test Which of these statements is true. a.A theory becomes a Law after it has been proven correct. b.A theory is accepted if it is reproduced by enough experiments. c.A theory is a guess one then performs experiments in order to test. d.We should withhold judgments on theories until they become Laws. e.None of the above.

2 Concept Test The difference between scientific laws and theories is: a.A theory is a guess that becomes a law when it has survived repeated testing. b.Nothing. c.Since 1900 no new theories have been sufficiently proved in order to meet the criteria of being a law. d.All of the above. e.None of the above.

2 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 hypothesis 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”

2 An Important Subtlety Multiple working hypotheses.

2 Homework #2 Due Monday 8-Sept: Read Chapter 3 Bennett (B3 on web page): 1.Give an example from the chapter of someone (other than Kepler) applying the scientific method? 2.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. Remember the Topic of Confusion!