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The speed of light is a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.

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My answer incorporates features of the earlier answers, but tries to clearly disentangle the implied uses of "speed" in space and in spacetime [when a phrase like 'slower in the dimension of time' is …
answered Mar 29 '17 by robphy
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In this passage by Rosser, $u=c\sin\theta$ is the spatial velocity, where $\theta$ is a parameter used in a "Loedel diagram" (see Wikipedia entry and Paul Gruner's Elementary geometric representation …
answered Jun 12 by robphy
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(This answer elaborates on the comment from @Armando .) Consider this spacetime diagram on rotated graph paper. Alice uses Minkowski-right triangle OPQ, with right-angle P and legs parallel to her …
answered Apr 13 '17 by robphy
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as the speed of a particle approaches c, its mass tends to infinity. While statements like this appear frequently in the literature (pop-sci and textbooks), it needs more modern terms and a more …
answered Feb 24 by robphy
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An enlightening (but possibly advanced) method to prove the constancy of the speed of light from the Lorentz boost transformation is to find the eigenvectors of the Lorentz boost. Two of the eigenvect …
answered May 23 '17 by robphy
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Maybe this reading of your question gets to what you are really asking. It's not really about the "speed of light" [electromagnetic radiation], but about the maximum signal speed. The eigenvectors o …
answered Mar 23 '18 by robphy
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By analogy with the fine-structure constant (which is dimensionless): $\alpha=\displaystyle\frac{1}{4\pi\epsilon_0}\frac{e^2}{\hbar c},$ one can form a dimensionless quantity: $\displaystyle G \frac{m …
answered May 26 by robphy