Mystery #2Tier 3time and motion

Why would a clock on a super-fast spaceship tick slower than one back home?

Time feels like the one thing you can always trust. A second is a second, tick after steady tick. Yet if you climbed aboard a spaceship and raced across the galaxy, your clock would quietly fall behind the ones back home. Why would simply moving fast make time itself slow down?

Two scientists beside the first caesium atomic clock at Britain's National Physical Laboratory, the kind of clock accurate enough to catch time itself running slow — Photo: National Physical Laboratory · Public domain · via Wikimedia Commons

Your guess

Why do you think a moving clock might tick more slowly than one standing still?

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