How Science Works • Philosophers • Religious Evangelists • Politicians • Salespeople • Scientists • Crackpots • All sound very sure of their beliefs. • Why should we believe one sort of “knowledge” over any other?
What is science? • A method by which to understand nature. • A quest for understanding nature. • A quantitative understanding of physical reality
What is science? A method by which to understand nature. A quest for understanding nature. A quantitative understanding of physical reality
The Scientific Method: Observation, Reason, Experiment Experimentally Testable Quantitative Predictions Observed facts
The Scientific Method: Ask Nature • The scientific method is a three-step process • Observe the phenomenon that you are studying in as many ways as possible. In some cases, the only thing you can do is observe nature. Astronomers are usually in this situation, because they cannot get their hands on the objects that they study. Or you may be able to design and carry out experiments that clarify how nature behaves. • Look for regularities. Form a hypothesis about what is happening. For example, the hypothesis may be a candidate physical law. The aim is that the hypothesis be more general than the specific examples of nature's behavior that it was designed to explain. • Test the hypothesis. Use it to make predictions & make experiments to test the predictions. • If the hypothesis fails even one test, then you have proved that it is wrong. Fixing it may require just a small change or it may require a completely different approach. • If it passes the test, our confidence in it is increased. It is in principle impossible to prove the hypothesis completely: we can never try all possible experiments, and so we can never be sure that we tested the hypothesis at its weakest point. But if it passes enough tests, we may get so confident in it that for all practical purposes we treat it as proved.
. The Scientific Method Observation Question Hypothesis Prediction Test does not support hypothesis: revise or discard hypothesis Test supports hypothesis: make additional predictions and test. Test: experiment or additional observations
How is science actually done: The peer-review process A scientist’s work must be scrutinized by other independent experts in the field before it is published.
Theory versus Law versus Hypothesis The hierarchy: Scientific Theory Law 1 Law 2 Hypothesis 6 Hypothesis 1 Hypothesis 4 Hypothesis 2 Hypothesis 8 Hypothesis 3 Hypothesis 5 Hypothesis 7 Hypothesis 9
Scientific Theory Scientific Theories are: well supported by evidence. what scientists are most certain about. Criteria:Theory must be falsifiable. • Theories allow for predictions which can be tested. Either verified or falsified by experiment or observation. Can a theory ever become fact or is it only a theory? What about: The atomic theory of matter The heliocentric theory of the Solar System The Big Bang theory The theory of biological evolution String or M theory
A case study: Gravitational Theory Newton’s universal LAW of gravitation • Newton’s Theory of Gravitation: • Objects with mass exert a force on one another. • Unified motion of objects on earth with motion of celestial objects • Predicted the existence of Neptune Problems: Mercury’s orbit showed slight perturbations that could not be accounted for under Newton's theory.
Einstein overturned Newton’s theory of gravitation with: The Theory of General Relativity • Accounted for perturbations in Mercury’s orbit • Predicted that mass bends light – verified by Sir Arthur Eddington in 1919
Note: General Relativity did not completely overturn all Newton’s ideas. We still use Newton’s law of gravity as an excellent approximation: It accurately describes and predicts all motion on earth and is used by NASA for space probe calculations. It is an excellent approximation, but Einstein’s theory is a better approximation. The theory that eventually replaces Einstein’s theory will be an even better one.
All scientific theories are open to scrutiny. • A scientific theory MUST be discarded if there is contradicting evidence. • All scientific data is subject to uncertainties. Warning: Manufacturing uncertainties. Often, people magnify the uncertainties inherent in science for financial or political gain. Example: the tobacco industry’s denial of cigarettes’ link to cancer
Three Important CharacteristicsRichard Feynman • The Test of Science is its Ability to Predict • Scientific Results Must be Repeatable • The Language of Science is Mathematics
The Language of Science is Mathematics • The natural language in which to state a theory is mathematics. • Of course, underlying principles may have to be stated in words. Other “languages” may be useful, too, like geometrical concepts and pictures. • But you have to be able to get numbers out of a theory, or you can’t test it. And nobody is likely to build a rocket that will get you successfully to the Moon unless a lot of physics and a lot of engineering are carried out quantitatively correctly.
Ways to Recognize Pseudoscience • Not quantitative • Not predictive • Not falsifiable • The phenomena that gave rise to the theory are unreliable. E. g., demonstrations of telepathy. • You cannot repeat the observations that gave rise to the theory. E. g., “Little green men in a flying saucer picked me up and took me to Venus, but I’m special: they won’t appear for you.” Or: only the originator of the theory is allowed to have control of the environment when the experiment is done. • The theory makes no contact with other well established science. • Unprofessional lack of rigor is, at the very least, suspicious. Examples: lack of statistical rigor, lack of “control samples” that are expected not to show the effect. Also: secretiveness, vagueness, … • Demonstrable inconsistencies or failures are indisputable disproofs (but they are nevertheless often ignored!)
Science gathers knowledge of the world and attempts to condense it into testable laws and principles by a wide-ranging set of methods. The features that distinguish it from pseudoscience are, 1) repeatability: the same phenomenon is sought again, preferably by independent investigation, and the interpretation given it confirmed or discarded by means of analysis and experimentation. 2) economy: scientists attempt to abstract the information into the form that is simplest and most esthetically pleasing while yielding the largest amount of information . 3) mensuration: if something can be properly measured, using universally accepted scales, generalizations about it will be rendered less ambiguous. 4) heuristic: the best science stimulates further discovery, often in unpredictable new directions, whose content confirms or modifies the parent formulation. • E. O. Wilson