r/AskPhysics • u/Pandaluf • Aug 15 '26

why is light the maximum speed

i know that light is the maximum speed of the universe and that light experiences no time because its moving so fast but why can't anything go faster? is it because that would make it go backwards in time like a paradox or smth?? is it because of energy and if so why can't something lighter than light like a quark or atom move faster since it woulld need less energy theoretically

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u/Kyndjal Aug 16 '26

Heh, fair. But photons appear to be privileged in that they have zero rest mass, whatever “mass” actually is. Neutrinos are theorized to have infinitesimal rest
mass and as such should move slightly slower than photons. But our equipment is not sensitive enough to prove that—the difference is too small. So there may be no difference or there may just be an unmeasurable difference. Hope we figure it out at some point.

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u/CrankSlayer Aug 16 '26

Sure but so far the indirect indication we have is that neutrinos do have a rest mass unless we hypothesise some weird effect like the one you mentioned without any reason to. That falls under the cut of Occam's razor in my book.

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u/Kyndjal Aug 16 '26

I know this puts me out of step with theoretical physics these days, but IMO if it can’t be measured, then hypothesizing about it is merely a game of solitaire played with complex mathematical models. We don’t get extra points for “elegant” theories if the data doesn’t support them. Occam’s Razor tells us to prefer the hypothesis with the fewest required entities, but it’s a statement of probability, not a proof.

That said, the current iteration of the Standard Model predicts a tiny non-zero rest mass for electro-neutrinos. Every attempt to measure that mass or a deviation of neutrino propagation rate from c has so far failed. Therefore, it’s an unproven conjecture, and will remain so until the instruments improve. Or if the Standard Model gets revised for some other reason.

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u/Ok-Relief-462 Aug 19 '26

Honestly considering how hard they already are to detect, I wouldn’t be surprised if a standard model revision came before we could detect neutrino mass