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Talk:Theory of relativity (view source)
Revision as of 23:38, November 13, 2009
, 23:38, November 13, 2009→Comments on Newtonian Mechanics: new section
::: As for "absurd physical discontinuities," the supposed discontinuity listed in the article is the same for ''both'' relativity and Newtonian physics: the limit of mv as m goes to 0 and v goes to c is just 0, while the momentum of light is nonzero. But so what? A photon is not the ''limit'' of a shrinking mass, so this limit isn't supposed to equal the momentum of a photon. This is not a "discontinuity" in the laws of physics, simply a misleading mathematical argument. --[[User:NgSmith|NgSmith]]
::: As for "absurd physical discontinuities," the supposed discontinuity listed in the article is the same for ''both'' relativity and Newtonian physics: the limit of mv as m goes to 0 and v goes to c is just 0, while the momentum of light is nonzero. But so what? A photon is not the ''limit'' of a shrinking mass, so this limit isn't supposed to equal the momentum of a photon. This is not a "discontinuity" in the laws of physics, simply a misleading mathematical argument. --[[User:NgSmith|NgSmith]]
== Comments on Newtonian Mechanics ==
There are two aspects of Newtonian mechanics that are, I believe, misstated in this article.
One: several times the article claims that Newtonian mechanics predicts deflection of light by massive objects.
Newtonian physics did predict gravitational acceleration of light, ''back when light was thought to have mass, 200 years ago.'' But this "corpuscular" theory of light was abandoned long ago due to its false predictions, versus the growing evidence of light as a massless phenomenon. With massless light Newtonian mechanics does not predict any gravitational deflection at all.
It is misleading to represent that old theory, long since discredited, as "Newtonian mechanics," or to represent it as a present-day alternative to relativity. Newtonian mechanics does not model light as corpuscles, and does not claim that light is accelerated by gravity.
Two: the article makes fudge-factor statements like, "it is debatable how much deflection Newtonian mechanics should predict." No, it is not debatable at all: both Newtonian mechanics and relativity have well-defined, concrete laws that you can find in any physics textbook. There is no mystery or lingering uncertainty about what they say, and we know precisely what these laws predict about the path of a mass passing another mass.
It seems like the article is defending an incorrect prediction by arguing that the predicted value is still up for debate. But this is wrong; we know what the predicted value was, and should honestly accept that it does not match observation.--[[User:NgSmith|NgSmith]]