As I've seen this point made in the past, it's that travelling at a constant 1g acceleration the subjective time for an astronaut would be about 45 years in traversing the observable Universe (~14 billion light years).
That is, a comfortable and familiar acceleration gives a human-lifetime-equivalent journey (subjective time).
If you're planning a round-trip, you'll find rather more time has transpired on what used to be Earth.
That is, a comfortable and familiar acceleration gives a human-lifetime-equivalent journey (subjective time).
If you're planning a round-trip, you'll find rather more time has transpired on what used to be Earth.
<https://www.universetoday.com/129086/far-can-travel/>