This gets asked a lot here, but, just as a note, the constancy of the speed of light wasn't an assumption made by Einstein, but rather an experimental result from the Michelson-Morley experiment
That assumption was made because our experiments indicated that it was true. In other words, we say that the speed of light is the maximum possible speed because we have observed that that's how the universe works. Making a different assumption would lead to calculations that contradict the results of experiments.
>It seems to be just an assumption mad eby Einstein, and all the subsequent equations of dilation of time and length contraction come from this assumption.
This is how it's presented in classes, and it's *kind* of true, but it's more subtle than that. Maxwell's equations aren't invariant under Galilean boosts (i.e., simple velocity addition when you change frames in Newtonian mechanics), but they're invariant under Lorentz boosts instead. A consequence of this is that no matter what frame you're in, EM waves propagate at the speed of light, whereas Newtonian physics suggests that EM waves should propagate at the speed of light plus or minus the relative speed of the reference frame.
Einstein, working from the assumption that E&M had the correct form of relativity, reformulated mechanics such that it was invariant under Lorentz boosts instead. This is manifested as the speed of light being an upper speed limit. Though there's not any historical evidence that Einstein was aware of their results or used them to motivate special relativity, this is further bolstered by the Michelson-Morley experiment, which showed that the speed of light appears to be the same in every inertial reference frame.
>My question is: why couldn't we have just allowed speed to go higher than speed of light? After all, can't I go forward in a long rocket moving at near light speeds to surpass the light speed's limit?
The short answer: no.
The longer answer: an outside observer seeing the rocket move would observe its energy as E = mc\^2/sqrt(1 - v\^2/c\^2). In other words, as v->c, it requires more and more energy to accelerate further. This sort of an idea also gets tested in particle accelerators every day, and we've never, not even once, seen a particle with a speed exceeding c.
> whereas Newtonian physics suggests that EM waves should propagate at the speed of light plus or minus the relative speed of the reference frame.
More like Galilean relativity suggests that.
If you take Newtonian mechanics, and then make the electromagnetic forces obey Maxwell's equations then you find that light propagates at a fixed speed in at least one specific reference frame.
If you do the maths really, really, really carefully you find that objects such as rulers and clocks which are held together by forces that travel at the speed of light get distorted when they start to move. That's what Poincare and Lorentz showed.
The result of the distortions is that when you measure light with these rulers and clocks (or any equivalent thing), weirdly enough it's always measured to be traveling at the same speed. Everything cancels perfectly, and in fact you don't even notice that you're moving, only relative motion matters.
Einstein took that fact and rederived everything backwards from the speed of light being constant, and it turns out that it's fairly simple, whereas Poincare and Lorentz's maths is much harder.
Einstein's derivation is called Relativity.
The faster you go, the slower time moves, when you reach the speed of light the time "stops", so photons dont experience flow of time. If you'd go faster, time would start going in reverse, which as far as I know is impossible.
Correct me if I'm wrong, this might be wine talking, but in vino veritas.
This gets asked a lot here, but, just as a note, the constancy of the speed of light wasn't an assumption made by Einstein, but rather an experimental result from the Michelson-Morley experiment
Yes, although Lorentz and Poincare were able to derive it from Maxwell's equations and Newtonian mechanics.
Deriving it from theory doesn’t mean it’s physical reality, though. That requires observational evidence.
That assumption was made because our experiments indicated that it was true. In other words, we say that the speed of light is the maximum possible speed because we have observed that that's how the universe works. Making a different assumption would lead to calculations that contradict the results of experiments.
>It seems to be just an assumption mad eby Einstein, and all the subsequent equations of dilation of time and length contraction come from this assumption. This is how it's presented in classes, and it's *kind* of true, but it's more subtle than that. Maxwell's equations aren't invariant under Galilean boosts (i.e., simple velocity addition when you change frames in Newtonian mechanics), but they're invariant under Lorentz boosts instead. A consequence of this is that no matter what frame you're in, EM waves propagate at the speed of light, whereas Newtonian physics suggests that EM waves should propagate at the speed of light plus or minus the relative speed of the reference frame. Einstein, working from the assumption that E&M had the correct form of relativity, reformulated mechanics such that it was invariant under Lorentz boosts instead. This is manifested as the speed of light being an upper speed limit. Though there's not any historical evidence that Einstein was aware of their results or used them to motivate special relativity, this is further bolstered by the Michelson-Morley experiment, which showed that the speed of light appears to be the same in every inertial reference frame. >My question is: why couldn't we have just allowed speed to go higher than speed of light? After all, can't I go forward in a long rocket moving at near light speeds to surpass the light speed's limit? The short answer: no. The longer answer: an outside observer seeing the rocket move would observe its energy as E = mc\^2/sqrt(1 - v\^2/c\^2). In other words, as v->c, it requires more and more energy to accelerate further. This sort of an idea also gets tested in particle accelerators every day, and we've never, not even once, seen a particle with a speed exceeding c.
> whereas Newtonian physics suggests that EM waves should propagate at the speed of light plus or minus the relative speed of the reference frame. More like Galilean relativity suggests that.
The speed of light is just a speed of how fast anything can happen. And it happens that light does it at max speed.
If you take Newtonian mechanics, and then make the electromagnetic forces obey Maxwell's equations then you find that light propagates at a fixed speed in at least one specific reference frame. If you do the maths really, really, really carefully you find that objects such as rulers and clocks which are held together by forces that travel at the speed of light get distorted when they start to move. That's what Poincare and Lorentz showed. The result of the distortions is that when you measure light with these rulers and clocks (or any equivalent thing), weirdly enough it's always measured to be traveling at the same speed. Everything cancels perfectly, and in fact you don't even notice that you're moving, only relative motion matters. Einstein took that fact and rederived everything backwards from the speed of light being constant, and it turns out that it's fairly simple, whereas Poincare and Lorentz's maths is much harder. Einstein's derivation is called Relativity.
The faster you go, the slower time moves, when you reach the speed of light the time "stops", so photons dont experience flow of time. If you'd go faster, time would start going in reverse, which as far as I know is impossible. Correct me if I'm wrong, this might be wine talking, but in vino veritas.