Time dilation
Time dilation is the difference in elapsed time as measured by two clocks, either because of a relative velocity as predicted by special relativity, or a difference in gravitational potential. When an object moves very fast, time passes more slowly for that object than for someone at rest. The faster it travels, the greater the effect. Time dilation matters because it is routinely accounted for in particle physics and is of practical concern in satellite navigation systems such as GPS and Galileo. Although minimal at everyday speeds—an astronaut aboard the International Space Station ages about 5 milliseconds less than someone on Earth over 6 months—these predictions have been repeatedly confirmed by experiment.
Sources
- en.wikipedia.org: “Time dilation is the difference in elapsed time as measured by two clocks, either because of a relative velocity, a consequence of special relativity, or a difference in gravitational potential between their locations due to gravitational time dilation.”
- en.wikipedia.org: “These predictions of the theory of relativity have been repeatedly confirmed by experiment, and they are of practical concern, for instance in the operation of satellite navigation systems such as GPS and Galileo.”
- en.wikipedia.org: “After 6 months on the International Space Station (ISS), orbiting Earth at a speed of about 7,700 m/s, an astronaut will age about 5 milliseconds less than a person on Earth.”