The Natural Sciences as AoK

1. The Natural Sciences as AoK

2. What is Natural Science? • “Science may be described as the art of systematic oversimplification.” --Karl Popper (1902-1994) • “Science is a way of thinking more than it is a body of knowledge.” --Carl Sagan (1934-1996)

3. The Scientific Method • Observartion • Hypothesis • Experiment • Law • Theory

4. The Scientific Method • Observe and record data • Classify relevant data • Search for a pattern in the data • Formulate a hypothesis • Make a predication based on steps 1-4 • Test prediction using an experiment • If experiment confirms hypothesis = discovery of a scientific law • Controllability: vary only 1 factor at a time to help isolate cause of phenomenon being investigated • Measurability: relevant variables must be measurable, which allows precisions & objectivity • Repeatability: others must be able to repeat experiment & confirm results • Develop a theory, which explains & unifies various laws based on an underlying principle: a good theory explains why laws are the way they are & provides focus for further research* * Lagemaat, Richard van de, Theory of Knowlesde: for the IB Diploma, Cambridge: Cambridge University Press, 2009, p.226.

5. The Scientific Method : An Example Observation: • Observation of the nighttime sky over the centuries became better, leading to a more complicated picture of heavenly bodies • Ptolemy’s geocentric model of the universe become less orderly and more messy, needing more & more new explanations to make sense of the model

6. The Scientific Method : An Example Hypothesis • Nicolaus Copernicus (1473-1543) proposes a heliocentric model of the universe with the sun at the center & the Earth revolving around the sun • Simpler & more elegant explanation

7. The Scientific Method : An Example Prediction • In Ptolemaic model, Venus always same size • In Copernican model, Venus’ size should vary depending on its distance from the Earth • 1609: Galileo (1564-1642) uses his telescope to observe that Venus’ size does vary depending on its relative position from Earth just as Copernicus had predicted

8. The Scientific Method : An Example Law • Johann Kepler (1571-1630) used the above observations & discoveries in his study of the heavenly bodies • Kepler developed his laws of planetary motion, which included his assertion than planets revolve around the Sun in ellipses

9. The Scientific Method : An Example Theory • Isaac Newton (1642-1727) devised the theory of gravity • Theory of Gravity: there is a force of attraction between objects, directly proportional to their masses & inversely proportional to the square of the distance between objects (2x distance: ¼ gravitational attraction) • Broader theory of gravity explained why apples fall (probably apocryphal story), people have weight, movement of the tides & led to discovery of Uranus (1781) & Neptune (1846)

10. The Scientific Method : Consider • Scientific progress needs a background of careful observation (Kepler need Tycho Brahe, 1546-1601) • Technology can strengthen powers of observation (telescope & microscope) • Imagination has an important role in scientific discoveries (Copernicus saw what so many others had not seen*) • Mathematics plays a key function; it gives expression & precision (Newton’s laws) *Aristarchus (3rd century BCE Greek astronomer proposed a heliocentric universe)

11. The Scientific Method : Problems Observation • Relevance: humans always begin with an idea(s) of what is or is not relevant to a problem • Selective nature of perception: possible to overlook or not anticipate something that turns out to be relevant (# people in a room during an experiment) • Expectations can influence observations • Expert seeing: practice & experience to look in microscope or read an ultrasound • Observer effect: an of observation can affect what is observed (thermometer)

12. The Scientific Method : Problems Hypothesis • Confirmation bias: accept evidence that confirms biases & reject evidence that does not • Charles Darwin (1809-1882): “’I followed a golden rule, namely that whenever a new observation or thought came across me, which was opposed to my general results, I make a memorandum of it without fail at once; for I had found by experience that such facts and thoughts were far more apt to escape from the memory than favorable ones.” (Lagermaat, p. 230)

13. The Scientific Method : Problems Hypothesis • Background assumptions: humans make assumptions that may prove to be incorrect (notion that stars were close to the Earth) • Different hypotheses can be consistent with a set of data • Principle of Simplicity: in the presence of two or more competing theories that make the same predictions… the simpler theory is to be preferred

14. The Scientific Method : Problems Law • Problem of Induction: move from observed to unobserved (all swans are white or all metals expand when heated) • Practical Problems: how many observations are needed? • Theoretical Problems: • science is based on empricism (no claims beyond the observed) • grounding in observation gives authority to science not found in pseudo-science • do we refuse to make claims that go beyond what has been observed? • how do new laws & discoveries get made • allow right of scientists to reason from particular to general • abandon claim that science is strictly emprical?