Say in an unaccelerated frame "S" a "isolated body A" moves with constancy of velocity , can we predict mathematically that any other such body B will move with same velocity in that frame....

My another question is that can one predict mathatically that "A will the same behaviour in any other unaccelerated frame say T"....

OR if they have to be accepted as postulates.

  • $\begingroup$ Does "because it describes what we observe fairly well" count as an answer? $\endgroup$
    – Kyle Kanos
    Nov 26, 2015 at 17:19
  • $\begingroup$ @Kyle Kanos 7 what is significant is that is it really thr way you are saying , had we really made that assumptions and since exp. had congurent results we just said that they are true indeed...Please respond if u know it. $\endgroup$ Nov 27, 2015 at 1:14
  • $\begingroup$ Please don't use all caps to emphasize something. On the internet, it comes off as shouting. $\endgroup$
    – HDE 226868
    Nov 27, 2015 at 14:50
  • $\begingroup$ I will take care of this $\endgroup$ Nov 28, 2015 at 10:52

1 Answer 1


Physics is an observational science. It measures and observes the way nature behaves, and ever since Newton, models these measurements and observations with mathematics.

Mathematics is a discipline where one starts with axioms uses logic and arrives to theorems and expressions that can be proven using the axioms and other theorems. One ends a proof in mathematics with QED ( quod erat demostrandum, i.e. which should be demonstrated). Proofs belong to mathematics.

Physics in addition to the mathematical axioms that control the mathematical formulas used, has postulates, or laws, that make a one to one correspondence with physical measurements and observations. The postulates/laws are a distillate of innumerable observations and measurements. They can never be proven, they are assumed. In contrast to a mathematical system, the models of physics are validated, i.e. follow the mathematical predictions usually for certain regions of variables. Newtonian laws are not useful for high energies where special relativity or general relatitivy postulates had to be devised to explain observations.

A physics theory can be falsified , but not proven.

Your question depends on the validity of Newton's laws of motion, and the Galilean transformations. These work exceptionally well in everyday life, so there they are validated and all consequences of the mathematical models are expected to hold. They are falsified for elementary particles and high energies and for high gravitational masses where other postulates were posited so that observations could be fitted with a mathematical model.


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