

How Far Can One Travel From Earth? - cominatchu
http://en.wikipedia.org/wiki/Special_Relativity#How_far_can_one_travel_from_the_Earth.3F

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hannibal5
assuming that space traveler had the incredible amount of energy to accelerate
long periods of time, interstellar medium would be the limiting factor. There
would be upper limit (say 90-99% of the speed of the light) and after that
particles, molecules and dust in the space would bee too energetic for the
space ship to stay intact.

