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Talk:Theory of relativity (view source)
Revision as of 02:44, November 19, 2009
, 02:44, November 19, 2009→Comments on Newtonian Mechanics
:::::: The ''rest mass'' of the photon is zero. The photon is not at rest, and does respond to Newtonian gravity. If you think otherwise, then I suggest that you find some sources. [[User:RSchlafly|RSchlafly]] 12:14, 18 November 2009 (EST)
:::::: The ''rest mass'' of the photon is zero. The photon is not at rest, and does respond to Newtonian gravity. If you think otherwise, then I suggest that you find some sources. [[User:RSchlafly|RSchlafly]] 12:14, 18 November 2009 (EST)
::::::: In Newtonian mechanics, "rest mass" is the only mass there is. Newtonian mechanics ''does not predict an increase of gravitational mass with velocity.'' Thus for a photon, the "m" in "F=GMm/rr" is unavoidably zero.
::::::: In relativity, an object's kinetic energy as well as its rest mass can contribute to space-time curvature, i.e. gravitation. But that simply isn't Newtonian mechanics anymore. If you start making relativistic arguments to put a nonzero value in GMm/rr, you may end up predicting deflection of light; but it is still wrong to say that ''Newtonian mechanics'' is making this prediction.
::::::: I must stress again that both relativity and Newtonian mechanics have very well-defined laws that are well understood. In Newtonian mechanics, you simply can't have a nonzero gravitational pull on a massless object. The law of universal gravitation is painfully clear on this point.--[[User:NgSmith|NgSmith]]