Why do astronauts age slower in space?

Time

Why do astronauts age slower in space?

Imagine you're on Earth and a friend travels to Mars at high speed. You both celebrate birthdays; you age normally, but your friend ages less.

Time stretches when you move fast. Your friend on Mars feels time slower because they're zooming through space.

Example

If you traveled to Mars at 99% the speed of light for what feels like 5 years, only 1 year would pass for you on Earth.

Remember this

Moving fast makes time slow down for you (time dilation).

Text adapted from Wikipedia, licensed under CC BY-SA 4.0.

Related concepts

Introduction to general relativity

Ever wondered why clocks on fast-moving planes tick slightly slower?

Twin paradox

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Global Positioning System

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Special relativity

Albert Einstein's special relativity paper introduced time dilation

Time dilation

Clocks run slower in stronger gravitational fields

Relativity of simultaneity

Simultaneity depends on the observer's motion

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