“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.”
Source: A Brief History of Time (1988), Ch. 1
Context: 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.
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Stephen Hawking 122
British theoretical physicist, cosmologist, and author 1942–2018Related quotes
"Matter" in Man's Right to Knowledge, 2nd series (1954), p. 10; also in Writings on Physics and Philosophy (1994) edited by Charles Paul P. Enz and Karl von Meyenn
Context: In the new pattern of thought we do not assume any longer the detached observer, occurring in the idealizations of this classical type of theory, but an observer who by his indeterminable effects creates a new situation, theoretically described as a new state of the observed system. In this way every observation is a singling out of a particular factual result, here and now, from the theoretical possibilities, therefore making obvious the discontinuous aspect of physical phenomena.
Nevertheless, there remains still in the new kind of theory an objective reality, inasmuch as these theories deny any possibility for the observer to influence the result of a measurement, once the experimental arrangement is chosen. Therefore particular qualities of an individual observer do not enter into the conceptual framework of the theory.
Context: Of course, we must avoid postulating a new element for each new phenomenon. But an equally serious mistake is to admit into the theory only those elements which can now be observed. For the purpose of a theory is not only to correlate the results of observations that we already know how to make, but also to suggest the need for new kinds of observations and to predict their results. In fact, the better a theory is able to suggest the need for new kinds of observations and to predict their results correctly, the more confidence we have that this theory is likely to be good representation of the actual properties of matter and not simply an empirical system especially chosen in such a way as to correlate a group of already known facts.
The System of the World (1800)
Introduction, A New Gravity Theory, p. xi
Reinventing Gravity (2008)
p, 125
What Mad Pursuit (1988)
If its predictions appear obvious to experimentalists, why would they need a theory?
What Mad Pursuit (1988)
New Pathways in Science: Messenger Lectures 1934 (1947), p. 211.
Ce n'est point l'observation mais la théorie qui m'a conduit à ce résultat que l'expérience a ensuite confirmé.
explaining how he was led to discover the law characterizing interference fringes, in [Œuvres complètes d'Augustin Fresnel, Imprimerie impériale, 1866, http://books.google.com/books?id=3QgAAAAAMAAJ, 61]