The Natural Sciences as AoK

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)

The Scientific Method

1. Observartion2. Hypothesis3. Experiment4. Law5. Theory

The Scientific Method

1. Observe and record data2. Classify relevant data3. Search for a pattern in the data4. Formulate a hypothesis5. Make a predication based on steps 1-46. Test prediction using an experiment7. 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

8. 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.

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

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

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

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

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)

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)

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)

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)

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

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?