Why does the speed of light have a speed limit? >tfw photons

TL;DR asking "why" is philosophy not science

"Why" is a pretty hard question OP. Far as I've seen in my education, we don't have a good explanation why our current model seems to be the way things are. Maybe things aren't actually this way and we're dumb. But we only know more or less how things work, not why they do.

>>7795643
Not Op. How does light have a speed limit? If photons have no mass and they travel freely in a vacuum, what is limiting how quickly light moves from one place to the next.

Inb4 google it, "science".

Can we discuss this or is it below a /sci/ence goy?

>>7795614
>Why does the speed of light have a speed limit?

tl;dr: if our universe is causal and local, we should expect a maximum speed at which events can cause other events.

Let's play God and imagine we're designing a new universe. The universe is some space, occupied by things, and stuff happens in it, to be very, very vague. What fundamental guiding principles should we use to build our new universe?

If you don't want everything to be totally chaotic, one guiding principle that you could have is causality: when two things A and B happen in our universe, they could either be unrelated, or related by causation: either A caused B or B caused A [1], and the laws of physics that you're going to design would tell you how this causation occurs.

Now, imagine two observers moving through your new universe, observing events A and B. Suppose observer 1 determines that A caused B: should observer 2 agree with this observation? You could say 'no', of course, and make up some rules to make this work out [2], but the alternative is cleaner, and also true of the real universe: all observers agree that A caused B, no matter what. This gives you an ordering of events in the universe, which in the real universe is measured by time.

If we have causality in our new universe, the next natural question is to ask how events become causally connected. Can an event happening at any point in the universe, affect every other point? Can the time between two events that are causally connected be arbitrarily short? Again, you could say 'yes', but this would be slightly unsettling: something happening right now in the Andromeda galaxy, for example, could kill us instantly.

If on the other hand, you say 'no', then you've introduced another guiding principle into the design of the new universe: locality. Something that happens at some point in space and time affects its immediate surroundings in space and time only, and does not immediately affect the whole universe at once.

>>7795738
Given causality and locality, perhaps the next most natural question is to ask how local is 'local', if A is an event and B is some other place, we can imagine a "sphere of causation", and ask how soon can A cause something at B. This is arbitrary, and if you set it to infinity, then you go back to the non-local universe in the previous paragraph, which as we said is slightly uncomfortable and isn't consistent with the real universe. So you've got to set some kind of maximum speed at which one event can cause another event. In our universe, this is precisely the speed of light.

Let's look at the consequences of such a choice: first, should all observers agree on this maximum speed? Well, yeah, otherwise there wouldn't be a maximum. So there you go: if you want a causal, local universe, you should expect a maximum speed at which events can cause other events. Does this have to be the speed of light? I suppose not: but built into the equations of electromagnetism, as verified by many, many experiments, is a speed that all observers seem to agree on, which is precisely the speed at which light propagates. That should give you a really, really good hint that this is the same maximum speed that you're looking for in our universe (of course, physicists took a little detour before coming to this realization!).

To sum up, if you want a universe in which you can causally connect events, and a universe in which causes result only in local effects, then we should expect some kind of speed limit at which effects from a cause can propagate. This maximum should be observer-independent (otherwise it wouldn't be a maximum). The speed of light is precisely such an observer-independent speed, and so we expect that it is precisely that speed limit. Every equation in modern physics has these assumptions at its core, and so far everything seems to be working relatively well, so we're pretty sure it's right!

>>7795725
The universe is dictated by the speed of c, or causality. Not necessarily the speed of light, light just happens to have no mass and so will travel at the maximum speed, which is c

>>7795794
Thanks, that's what I gathered from the other two posts. I feel like the speed of light as a phrase should be reworded to something like the speed of causality. "Light" seems like a misnomer and often times leads to confusion.

[Any event happening in one part of the universe cannot effect any thing in another part of the universe more quickly than an observed maximum speed of causality] does not seem like a difficult concept.

But maybe I'm making it too complicated.

>>7795848

yes, c is the speed of causality. that, however, will not make us change the name of it from "the speed of light." that's just what we call it, like the countless numbers of other misnomers in our language, science-related or not.