system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40k] Are other galaxies affected by the 40k races? Is there maybe a galaxy nearby that exists in relative peace? Would be possible to reach it using imperium technology?
gpt
Total 40k novice here aside from a few YouTube videos and video games I've played.  Imperium technology can not reliably travel that far away from known space and most likely would get lost in the warp rather than travel between galaxies.  The tyranids came into the galaxy from completely different angles and directions. This means either the galaxy is surrounded by tyranids or they travel much faster outside the galaxy than any known race.  The other evidence of the milky way being isolated is no known superior race like the old ones or their foes seemed to be interested in leaving the galaxy even when facing extinction.  Maybe there's something keeping the various races tied to the milky way like a barrier similar to star wars or Star Trek lore that makes travel dangerous if not impossible.  Maybe the tyranids are all the life outside of our galaxy if they weren't created by the old ones.