Main Question or Discussion Point
Why does light or anything have a finite speed? In E=mc2, it gives the constant of the speed of light but I don't understand why light has a maximum speed. Is there something that slows down light?
Yes, electromagnetic waves travel at different speeds in different media. This arises naturally from electromagnetic theory. Another (quantum) way of looking at light, however, is as photons -- particles that have wavelike properties*. Now, photons *always* travel at c, and the explanation for why light is slowed down in materials is that although each individual photon travels at c, photons are constantly being destroyed and recreated during their interactions with matter. So, the overall progress of the light through the medium is slowed down.I thought that light travels different speeds depending on what medium that it is in.
No, they don't travel at c because "something" in a vacuum is preventing them from moving any faster. They travel at c because that is a fundamental property of electromagnetic waves (as prescribed by the theory). Electromagnetic waves travel at c in a vacuum. Or, if you want to look at it from the photon picture, photons are massless particles, and special relativity restricts massless particles from moving at any speed other than c (they can neither move slower nor faster).Is it possible light goes a set speed because a vacuum is just another medium with things that slow light down?
Yes and no. Yes, that is just the speed at which light travels. No, it is not "random" in the sense of being arbitrary. It is predicted by theory and holds up in experiment.or is it just a random speed that light or whatever energy moves at?