Problem: once you reach “relativistic” speeds, time slows down. So you, on the space ship, might age only twenty years while heading towards the nearest alien planet. But in the meantime, earth may have aged 50,000 years.
Nobody you know will be around to greet you on your return...
One of the best intro themes of any cartoon - or TV show for that matter:
https://youtu.be/SIhEpjnaNlo