Time passes slightly slower at your feet than at your head.

Time feels like the background that everything else happens inside. Relativity says it is not that simple. NIST has measured gravitational time dilation over everyday height differences, including clocks separated by about a foot. Stronger gravity makes clocks tick slightly slower, and your feet are fractionally deeper in Earth's gravitational field than your head. The difference across a human body is absurdly tiny, but it is real in the physics sense. This is the rare fact where the universe is technically weird at the scale of standing still.

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