I want to try something in the future that scares me

Later on in my future want to go explore other planets in the whole universe. But it scares me because what if go for a month or two and then I come back to earth and the time changes . I like to  recall  to a movie that is called interstellar and they go out in space to look for another planet because earth is dying . Then by the time he comes to see his daughter she older then him . This is something that will scare me because if that really happened to me my brothers would've been older than me .