User blog comment:PitaKang/Funday Monday 3: What would an interstellar civilization look like?/@comment-32656-20130501080354/@comment-4621372-20130505125251

Yes, I know. But 0.5 light speed isn't enough to feel any significant effects of relativity.

NASA cannot detect subatomic particles that wuld cause such things. This isn't currently a problem- at light speed, it will become a problem-