Is it true that a person in space doesn’t get as old as if he was on the earth? — ASB, Chiapas, Mexico
The effects you are referring to are extremely subtle, so no one will ever notice them in an astronaut. But with ultraprecise clocks, it’s not hard to see strange effects altering the passage of time in space. There are actually two competing effects that alter the passage of time on a spaceship—one that slows the passage of time as a consequence of special relativity and the other that speeds the passage of time as a consequence of general relativity.
The time slowing effect is acceleration—a person or clock that takes a fast trip around the earth and then returns to the starting point will experience slightly less time than a person or clock that remained at the starting point. This effect is a consequence of acceleration and the changing relationships between space and time that come with different velocities.
The time speeding effect is gravitational redshift—a person or clock that is farther from the earth’s center experiences slightly more time than a person or clock that remains at the earth’s surface. This effect is a consequence of the decreased potential energy that comes with being deeper in the earth’s gravitational potential well.