In a vacuum, the speed of light is at a mind-bending 300,000 kilometres per second. That’s not just very fast, it’s as fast as it is physically possible for anything to move.
The insight that light speed is a fundamental limit on motion is one of the keys to Einstein’s theories of relativity, but why is it so?
In this video from Fermilab, particle physicist Don Lincoln explains why the speed of light is as quick as it gets.
Related reading: Why can’t anything travel faster than light
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