Speed limit
Why nothing can go faster than the speed of light? (Light traveling in a vacuum, that is).
The thing is, it has little to do with speed, and even less with light. It has all to do with the fact that space and time are not separate entities. What the hell do I mean?
Let me start with an (apocryphal) story. In the old days, Egyptians used to measure distances in palms, but not any distance, only horizontal distances. For vertical distances, they used cubits. A room could be 45 palms wide and 10 cubits tall. With this measures they could normally do all their work, measure the areas of a pyramid in square palms and its height in cubits, etc.
But at some point they noticed a strange property of cubits and palms. If you have a stick standing more or less vertically, and that is, say, 1 cubit tall, then its shadow as seen from above was at most 6.973 palms long. Even more, when the same stick was laid horizontally, it measured exactly 6.973 palms. And more surprisingly, that happened for a stick of any size.
What was happening there? They noticed how vertical distances seemed to have a relationship with horizontal ones, and that a “universal constant” arised: c = 6.973 palms/cubit. If you took any object of a certain height, you could be sure that its perpendicular shadow would never be larger than c times its height.
That “horizontal-vertical universal limit”, and the constant c associated to it, of course has nothing to do with the kind of objects, or the any limit in the nature of distances. It has to do with the fact that they are measuring two things (horizontal and vertical distances), with their respective different units (palms and cubits), that are essentially the same.
I hope Egyptians will forgive me for such an invented example...
Now, what's the matter with the speed of light? It's exactly the same thing, except instead of talking about “horizontal distances” and “vertical distances” we are talking about “distances” (or “space” if you prefer) and “time”. Even if we intuitively think they are very different, they are the same in a way. And the fact that we use two different units for them (meters and seconds) makes a “universal constant” arise, c = 299792458 m/s. This constant has nothing to do with there being a speed limit more than the fact that speed itself (distance/time) is a unitless quantity, as we are dividing quantities that are of the same kind, but we insist in assigning different units to them. It has nothing to do with the objects moving in space, it has to do with space and time themselves.
And that, by the way, is also why physicist often like to talk about “spacetime” instead of “space and time”.
As for light, as it has zero rest mass, it necessarily moves at the “speed limit”, as any other object with zero rest mass, a consequence of what Einstein found out in his theory of relativity. Or, talking like our helpful Egyptians, light and any other massless particle are always a horizontal stick.
I don't think I've ever seen it explained like that, but that's how it works as far as I know, and I was willing to share it with anyone that would be interested in it. So there it goes!