Christina Koch returned from a 328 mission aboard the ISS. In college we learned that she would not experience time the same as us on earth over the 328 days. How can this be true and by how much younger would she be than you or I?

Question

In my undergrad physics course we were taught the basics of relativity. It was explained to us that something moving near the speed of light can somewhat time travel when compared to a stationary observer. So, how much younger would [Astronaut Koch](https://www.google.com/amp/s/amp.usatoday.com/amp/4676940002) be than us and how does this phenomena work?

In: Physics

Answer 1

You are basically asking the same question as the Twin Paradox. If you send one away quickly in a rocket ship and after some time, the rocket turns around and comes back. The traveling twin would be younger.

[This Wikipedia article](https://en.m.wikipedia.org/wiki/Twin_paradox) does a pretty good job at explaining. Some of it is dense and not really ELI5, but it’s pretty good explanation.