arXiv:astro-ph/0509268astro-ph
The Long-Term Future of Space Travel
Early discovery. Linked by one identifiable commenter. This paper is outside the main ranking; a mention is not an endorsement.
Abstract
The fact that we apparently live in an accelerating universe places limitations on where humans might visit. If the current energy density of the universe is dominated by a cosmological constant, a rocket could reach a galaxy observed today at a redshift of 1.7 on a one-way journey or merely 0.65 on a round trip. Unfortunately these maximal trips are impractical as they require an infinite proper time to traverse. However, calculating the rocket trajectory in detail shows that a rocketeer could nearly reach such galaxies within a lifetime (a long lifetime admittedly -- about 100 years). For less negative values of $w$ the maximal redshift increases becoming infinite for $w\geq -1/3$.
There is actually a whole sequence of such limits: the visibility limit (where light emitted in the distant past reaches us now) is furthest out, then comes the reachability limit (where light emitted by us now can still be observed), then the round trip limit where we can send…
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