User blog comment:PitaKang/Funday Monday 3: What would an interstellar civilization look like?/@comment-32656-20130501080354/@comment-4621372-20130504131844

Is, actually. Think of it this way; if you run into a speck of paint blown about due to wind, you won't notice.

At far greater speeds, up in orbit, a speck of paint can put a crack in a window.

Now imagine that speck of paint (or, eh, hydrogen) moving at light speed. All that would be left if it hit you would be, maybe, a smear. The space ship walls or a magnetic field can protect you only a certain amount.