Tuesday, January 24, 2006

theoretical physics as a subject of science

theoretical physics sometimes is regarded as a subject of purely thinking. however this is not really true. nevertheless it is based on experiments, like any other scientific subject.

science is a method to understand nature, the key point of this method is that experiment is the only way to verify if the understanding is correct or not. any understanding by definition involves certain logic (sometimes the logic is precise, that is mathematics). so it is very correct to say

科学 (science) = 逻辑 (logic) +实证 (experiment).

take quantum mechanics as an example. there is no any conflict between above statement and the establishment of quantum mechnics. without relevant experiments, no one could even imagine out the physics of quantum mechanics, no matter how free his/her idea is. new logic and concepts have been cooperated in the new theory, of course. but the above statement never insists on that the logic should be the one in the old theory. by the way, the physicists who proposed quantum mechanics were pretty aware that their new theory has to recover the classical physics in the area where the old physics had been verified experimentally. actually, this was their main working point.

in fact, einstein established his general relativity in a similarily scientific way. the special relativity and newton's gravity physics are in conflict with each other. motivated by this problem, he went to the general relativity with an idea of the curved spacetime. what i mean here is that he didn't come to the general relativity from nothing, or from his free willing.

it might be misleading to emphazise on idea freely invention. even scientist great like einstein, who failed in his effort to find an unified theory of gravitional interaction and electromagnetic interaction. such an unification is just his willing.

it is well-known that based on the same experimental facts, scientists may propose different theories with possibly very different logic. there is no mechanical relations between experimental results and theories. scientists have enough freedom in this sense. again, it is new experiments which exclude wrong theories, pick out the (temperally) correct ones and may motivate new theories.

finally i would say that physics is always driven by experimental facts, by real problem. it would be dangerous to think that progresses are by people's willing. the current elementary particle theories (for example, supersymmetry) are focus on the gauge hierarchy problem, the newest approach in gravity physics tries to solve the conflict between the general relativity and quantum mechanics (superstring). and the most recent studies in theoretical physics are based on the challenge imposed by new measurements for the cosmological constant.

see also: http://www.rainbowplan.org/lib/dir02.txt


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