So you’re saying if they head back they’ll technically go back in time?
I don’t know if that’s how it will happen, because assuming we can go FTL, we’ll basically be making “shortcuts” in space. Mean we won’t be traveling in a straight line. Either we’ll bend space to move faster or we’ll create wormholes
No not back in time but time dilation.
When you travel at constant acceleration of 1g your speed will constantly increase. Faster you go more time dilation you will experience and you will hit near speed of light (not speed of light).
This means time will slow down for you and the ship.
For example...
You left Earth in 2023 at the age of 20...for Andromeda Galaxy at constant acceleration of 1G.
Time will slow down so much for you and your ship that you will cross entire Milkyway in 12 years and Reach Andromeda in 28 years.
However, millions of years will pass on the Earth.
So, if you come back to the Earth then you will age by 28 (for one way trip) + 28 (return trip) - 56 years . So your age will be 76 years..
However, at Earth, millions of years will pass(future) - nothing will remain same. Humans perhaps won't even exist
Relativity is wack lol
I can share you the video which explains this