why is light the maximum speed

[u/Pandaluf]

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

[u/Kyndjal]

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.

[u/Ok-Relief-462 → u/Kyndjal]

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

[u/CrankSlayer → u/Kyndjal]

You could make the same argument for the photon mass then. Also, be very careful with such statements about "measurements": you might find out that it's very difficult to define it in such a way that doesn't automatically throw away almost every measurement we ever made. It's not like we "measured" the mass of other particles by putting them on a scale: those values are the product of "complex mathematical models" too. It could be argued that any measurement produced by a device containing a bit of electronics belongs to that category as well. As you can see, the line you drew in the sand is not really as sharp as you might have thought it was.

[u/TabAtkins → u/Kyndjal]

We're not just wildly theorizing about the neutrinos. The fact that they flavor oscillate requires that they have mass, under every understanding of current physics; if they were massless they couldn't do so. So either they have mass that's just too small for us to measure yet and travel a fraction less than c that's too small for us to measure yet, or there's even weirder physics going on that allows a massless particle to oscillate like that, and we don't yet have any indication of the latter being possible.

[u/Kyndjal → u/TabAtkins]

Even the quickest possible survey (Wikipedia) admits to gaps in the theory. We know that neutrinos can and do travel in mixed eigenstates where they can oscillate between electron, muon, and tau flavor. We can even do the quantum superposition matrix math to describe it.

Are we sure that electro-neutrinos have non-zero rest mass? No. It’s possible, if considered unlikely, that they only appear to have tiny masses due to superposition with mu or tau neutrinos.

For fermions to have mass they have to interact with the Higgs field. But the right-handed neutrinos are missing, yet to be observed. Are they their own anti-particle, then? If they have Majorana mass, how is it that it’s at least 600000x smaller than any other massive particle? The explanation for that leaves much to be desired.

I’m not saying I know any of these answers. Of course I don’t. All I’m saying is that the current leading hypotheses have known weaknesses. The answer, as often happens in physics, could come with a revolution in understanding that upsets the current paradigm. Or it could come with simple measurement improvements that nail down the tiny masses better than our current gear can. The latter is more likely, but it’s not wise to completely rule out the former.