The Special Theory of Relativity: Feynman's Physics Explained
Nature has a strange rule: the speed of light is the same for all observers, no matter how fast they move. This simple fact has enormous consequences. If light's speed is absolute, then space and time cannot be. An observer rushing past you sees your clocks run slow and your meter sticks shrink in the direction of motion. Space and time are not a fixed background; they are a single 'space-time' whose measurements depend on motion — different perspectives of one reality, just as width and depth are different views of a solid.
The big idea
Because light's speed is fixed, space and time must stretch and shrink.
Think about it
If you flew past Earth at near light-speed, you'd see our clocks run slow — and we'd see yours run slow. How can both be true?
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