The weapons being used by combatants on both sides fired particle-sized rounds at relativistic speeds.

We've taken two long interstellar voyages at relativistic speeds.

Measure the length of an object, like a spacecraft, at relativistic speeds and you would measure a shorter length.

Now, when I find myself onboard a robot spacecraft traveling at relativistic speeds, I see that I must completely unfetter God.

"We might be doing something comparable to relativistic speeds."