What is very important to me is two points: A theory should be internally consistent and it should have some contact with observation. Well, I’m told by all the experts that this theory [String theory] is internally consistent, although they think up new interpretations every time I turn my back. But contact with reality? Nobody’s given me anything. I just watch. I’m somewhat unhappy that so many people are working on it. To me, as a physicist, it’s sort of sad that so many people at the same time work at something that doesn’t seem to have any contact with experiment. But that, to some extent, is due to the fact that we don’t have any great experimental puzzle to be thinking about. We have to supply the puzzles, and there aren’t that many puzzles right now.
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Telegdi, Valentine L. Interview by Sara Lippincott. Pasadena, California, March 4 and 9, 2002. Oral History Project, California Institute of Technology Archives. Retrieved January 11, 2010 from the World Wide Web: http://resolver.caltech.edu/CaltechOH:OH_Telegdi_VValentine Telegdi
» Valentine Telegdi - all quotes »
Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory.
Stephen Hawking
A logical theory may be tested by its capacity for dealing with puzzles, and it is a wholesome plan, in thinking about logic, to stock the mind with as many puzzles as possible, since these serve much the same purpose as is served by experiments in physical science.
Bertrand Russell
There can be no question that Darwin had nothing like sufficient evidence to establish his theory of evolution. ... Darwin’s model of evolution ... , being basically a theory of historical reconstruction, ... is impossible to verify by experiment or direct observation as is normal in science ... Moreover, the theory of evolution deals with a series of unique events, the origin of life, the origin of intelligence and so on. Unique events are unrepeatable and cannot be subjected to any sort of experimental investigation. ... His general theory, that all life on earth had originated and evolved by a gradual successive accumulation of fortuitous mutations, is still, as it was in Darwin’s time, a highly speculative hypothesis entirely without direct factual support and very far from that self-evident axiom some of its more aggressive advocates would have us believe. ... One might have expected that a theory of such cardinal importance, a theory that literally changed the world, would have been something more than metaphysics, something more than a myth.
Charles Darwin
A similar situation occurred in astronomy, where the Newtonian law of gravitation had been found to predict the orbits of the outer planets with great accuracy, but had failed with the orbits of Mercury and Venus. The relativity theory of gravitation had provided the necessary modification of Newton's law, and in working out the details of the new theory, Einstein had utilized the fact that Newtonian law gave the right result at great distances from the sun. Heisenberg, confronted with a similar problem, was able to avail himself of the fact that the classical mechanics gave the right result at great distances from the atomic nucleus. Here, and here alone Heisenberg's theory made contact with the world of the older physics.
James Jeans
This fact, that all charges are integral multiples of a fundamental unit, is still one of the unexplained puzzles of fundamental physics. It does not in any way contradict electromagnetic theory, but it is not predicted by it, and until we have a more fundamental theory that explains it, we shall not feel that we really understand electromagnetic phenomena thoroughly. Presumably its explanation will not come until we understand quantum theory more thoroughly than we do at present.
John C. Slater
Telegdi, Valentine
Teller, Edward
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