system
Given the following post, respond as if you're commenting on Reddit:
human
Can people age differently on other planets because of gravity/relativity and come back to earth younger than their siblings?

In some movies, people go to other planets and for numerous reasons, they age differently than people on earth. Some say a few actual hours on these planets can actually be years on earth. I understand the concept that time is calculated differently on other planets but can anyone go to another planet and come back to earth physically younger?
gpt
Yes, but not significantly.

Gravitational time dilation is indeed a *real* effect. It's not caused by timekeeping or convention. Time really does run slower if you're in a strong gravitational field.

*However*, the effect is almost always so small that it's impossible to measure without extremely sensitive equipment. The different in gravity between planets is too small for the age difference to be noticeable.

It only really becomes significant if you're right on top of a black hole. This is a pretty hostile environment, but theoretically you could put a space station there if the black hole is spinning fast enough. It's technically possible for a planet to be there too, but it's probably not very likely. You could hang out on top of a black hole for a while and come home a *lot* younger.

Of course, to get to the black hole and back, you'd probably want to fly in a really fast space-ship, which means you also get time dilation from speed anyway.