Mystery #1Tier 3light speed limit

Why is there a top speed in the universe that nothing can ever beat?

Cars have top speeds. So do runners and planes. But the universe itself has one final speed that nothing, no matter how powerful its engines, can ever beat: the speed of light. Why should there be a limit that even a spaceship with endless fuel could never cross?

A laser beam shooting up from a telescope dome straight into the glowing heart of the Milky Way, travelling at the one speed nothing can beat — Photo: ESO/Yuri Beletsky · CC BY 4.0 · via Wikimedia Commons

Your guess

What do you think stops anything from going faster and faster without end?

There's no single magic word to type, have a go in your own words, then reveal the answer to see how close you got.

Make a guess to unlock the hints and the answer.