How we do science? The scientific method. A duck s head. The problem is that it is pretty clear that there is not a single method that scientists use.

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1 How we do science? The scientific method A duck s head The problem is that it is pretty clear that there is not a single method that scientists use.

2 How we do science Scientific ways of knowing (Induction vs Deduction) A rabbit s head

3 Scientific Ways of Knowing Induction (or inductive logic) Proceeding from examples to general rules or principles Induction leads to empirical approaches of understanding Deduction (or deductive logic) Using rules to understand examples Deduction leads to theoretical approaches to understanding

4 Deductive Logic Premise 1: Every mammal has a heart. Premise 2: Every horse is a mammal Conclusion: Every horse has a heart.

5 Inductive logic Premise: Every horse that has ever been observed has a heart. Conclusion: Every horse has a heart.

6 Deduction & Induction Deduction Given Model/Concept Expected Data Induction Inferred Model/Concept <- Actual Data

7 Scientific Ways of Knowing Raphael s School of Athens

Scientific Ways of Knowing Plato Pointing upward, indicating that knowledge comes from pure thought, emphasizing theoretical models and a deductive approach.

8 Scientific Ways of Knowing Plato Pointing upward, indicating that knowledge comes from pure thought, emphasizing theoretical models and a deductive approach. Aristotle Pointing down, indicating that knowledge comes from the world, emphasizing empirical data and an inductive approach Science s intellectual underpinnings are philosophy.

9 Scientific Ways of Knowing Induction -> Approach is observing (Empiricists) 1. Natural Observation observation of natural system without manipulation 2. Experimentation observation of natural system wit manipulation Deduction -> Approach is modeling (Theoreticians) 1. Theoretical modeling quantitative models designed to make predictions of geometry or behavior of natural systems

10 Empirical Approach Empirical approaches require that data is collected from the natural world. Consequently, scientists are very careful about observations (something that everyone will agree on) versus inferences/interpretation (something based both on observations and an individual s perspective).

12 Make five observations about this cartoon.

13 Make five inferences based on your observations of this cartoon.

14 How do we know the Earth is round? Observation List five observations Inference/Interpretation Provide an inference that corresponds to each observation

Scientific Ways of Knowing Induction -> Approach is observing (Empiricists) 1. Natural Observation observation of natural system without manipulation 2.

15 Scientific Ways of Knowing Induction -> Approach is observing (Empiricists) 1. Natural Observation observation of natural system without manipulation 2. Experimentation observation of natural system wit manipulation Deduction -> Approach is modeling (Theoreticians) 1. Theoretical modeling quantitative models designed to make predictions of geometry or behavior of natural systems You can see a lot just by observing. Yogi Berra

16 Ptolmey used natural observation to propose Geocentrism: The Earth is at the center of the solar system, and the planets and the sun rotate around the Earth Ptolmey ( C.E.), aka Claudius Ptolemaeus Lived and worked in Alexandria, Egypt For the record, Aristotle proposed this earlier.

17 Copernicus used natural observation to propose Heliocentrism: The sun is at the center of the solar system, and the planets and the Earth rotate around the Sun Nicolaus Copernicus ( CE) De revolutionibus orbium coelestium libri vi Six Books Concerning the Revolutions of the Heavenly Orbs (1543 CE)

18 Geocentrism and Heliocentrism are both theories Scientific theory Systematic sets of concepts that provide explanations for observing patterns in nature. Theories provide frameworks for relating data & guiding future research. Theories change as new data become available. Scientific hypotheses a tentative explanation that accounts for a set of facts and can be tested by further investigation. The colloquial use of theory is very different from a scientific theory : A everyday theory is a scientific hypothesis.

19 Geocentrism! Heliocentrism! Who was right? Let s look at the evidence!

20 Evidence = Relevant data & Interpretation

21 What are the relevant observations that can be used as evidence for geocentrism or heliocentrism? 1) The sun rises and sets every day (each 24 hours)

22 2) The moon goes from fully illuminated to dark to fully illuminated every ~29 days.

23 3) Sun, Moon, and planets all move in a single plane in space, called the ecliptic

24 The sun and some planets on the ecliptic (red dashed line)

25 4) The Sun does not always cover the same stars in the sky. In fact, we can divide the sky into 12 more-or-less equal parts that lie along the ecliptic. These are the signs of the zodiacs. It takes the sun ~365 days to make it through all the signs of the zodiac.

26 360 panorama of the Zodiac Zodiac from 500s (Israel)

27 Group work In groups, using the handouts, figure out how the first four pieces of evidence could be use to explain EITHER geocentrism or heliocentrism.

28 One last relevant observation 5) Some planets (Mars, Jupiter, Saturn) all appear to have retrograde motion. That means, they move general forward (east to west), but occasionally move backward (west to east) for short periods of time. One picture, per night, of Mars. The movement is judged by the background stars.

Rather, planets are attached to smaller spheres (epicycles)

29 Ptolemy s solution: The epicycles Planets are not attached directly to the concentric spheres themselves. Rather, planets are attached to smaller spheres (epicycles) which themselves are attached to the big, crystalline concentric spheres (deferents).

30 Copernicus solution It is an optical illusion for planets that are further from the sun than we are.

31 Actually, retrograde motion is a necessary consequence of the orbits, a type of optical illusion, if you will.

32 Two Scientific Theories Both the theories of Ptolemy and Copernicus actually fit the available evidence- what are you going to do? Hey, who cares who is right, at least we are in color!

33 What makes a good scientific theory? A good scientific theory: 1) Has logical consistency - parts of it don t contradict other parts 2) Agrees with the data 3) Suggests verifiable causes that explain and predict 4) Advanced comparisons (simplicity, tradeoff of generality and specificity, distinction between non-fatal difficulties and fatal difficulties)

34 Occam's Razor Named after the English philosopher, William of Occam (1300s). Two or more models accurately explain the observations? No Problem!!! Best model is the simplest one fewest assumptions/modification needed to fit the observations. I m the original KISS guy - Keep it simple, stupid a.k.a the Principle of Parsimony (died in the Black Death)

35 Ptolemy vs. Copernicus So, what theory is most acceptable? Occam says Copernicus Won t really know until Galileo We have a winner!

36 The resolution was provided by Galileo, using new technology. Galileo Galilei ( ) I m not feeling very comfortable in this highly starched shirt.

$(refractor,$

37 Ye olde telescope (refractor, for you astronomical weanies)

38 New technology allowed two new observations 1) The moons of Jupiter 2) The phases of Venus

39 The Ptolemaic system and the Copernican system made different predictions abound the shadows on Venus. Geocentrism Heliocentrism

40 Back to Heliocentrism New technology (telescope) allowed Galileo to make observations that are consistent with Heliocentrism and not with an Geocentrism. Result is the Heliocentrism is adopted by scientific community. Vindicated! (but happily very dead)

41 The list of the whole narrative: 1) Aristotle proposes theory (Geocentrism) 2) Ptolemy finds data (retrograde motion) that doesn't fit with theory 3) Ptolemy has two choices. a: propose new theory or b: modify old theory to fit new data (which he decides to do) 4) Copernicus comes up with new theory (Heliocentrism) using exactly the same data as Ptolemy. 5) Using Occam s razor (the best solution is the simplest), Copernicus model is superior. The idea is resisted because of social concerns, pre-conceived assumptions, and lack of understanding of physics. Yet, the model is used because of its predictive power, but not adopted as reality. 6) New technology (telescope) allows Galileo to make observation (phases of Venus, Moons of Jupiter) that are consistent with Heliocentrism and not with an Earth-centered Universe. 7) Heliocentrism is adopted by scientists.

42 The scientific method State the problem Gather information about the problem Form a hypothesis Perform an experiment to test the hypothesis Record and analyze your data State a conclusion

43 Copernicus

44 Galileo

45 What are the points of this example:

46 Did Copernicus know how big a deal this was? Yes. Knew about planetary motion by He did not, however, publish his book De revolutionibus until 1543, the year he died (and thus avoided problems). My momma raised no fool.

47 Others were less lucky (and more outspoken) than Copernicus. Galileo Galilei ( ) I m not feeling even less comfortable in this highly starched shirt.

Galileo was subject to the Inquisition, because heliocentrism was a heresy. He was put under house arrest until his death in 1642.

48 Galileo was subject to the Inquisition, because heliocentrism was a heresy. He was put under house arrest until his death in But, and this is big but, it is there that he did arguable most important work and developed a whole other way of knowing : Experimentation More next time! Forget experimentation, I ll sell my telescope on ebay and make a quick buck.

Observing the Solar System 20-1

Observing the Solar System 20-1 Ancient Observations The ancient Greeks observed the sky and noticed that the moon, sun, and stars seemed to move in a circle around the Earth. It seemed that the Earth