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Relativity makes time tick at different rates. Relativity makes time tick at different rates.

Time runs at different speeds

By Peter Teoh, Science Writer

Einstein showed that time is flexible. Move fast or sit deep in gravity, and your clock ticks more slowly than one far away.

Explainer: Relativity in everyday tech

Focus: GPS satellites experience both special and general relativity. Their high speed slows their clocks, but weaker gravity speeds them up. Engineers correct for both effects so your phone can locate you accurately.

This is a form of time travel: you can move into the future by traveling fast, but you cannot go back. The effects are small at human speeds, but real and measurable.

Summary of Key Ideas:

  • Time dilation depends on speed and gravity.
  • GPS works only because relativity corrections are applied.
  • Forward time travel is possible; backward is not.

Side Notes

  • Astronauts age slightly less than people on Earth.
  • Time dilation has been measured with atomic clocks.
  • Relativistic timekeeping for space navigation.
  • Precision clocks as gravity sensors.

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