Einstein’s theory of relativity basically means the faster you go the slower everything seems. Go fast enough and the world will seem to have been set on pause while to the world you will be moving too quickly for their eyes to perceive. So long as you’re moving you would be invisible to the naked, non-accelerated eye.
The alien species of this episode has been improbably accelerated by radiation. I say improbable because they ignore a lot of basics on this one. I checked online to see if anyone else had a problem and found Melissa N. Hayes-Gehrke via Wikipedia (oh, interwebs).
The concept was interesting, but the follow-through was just upsetting. Maybe they could have excused some of their timeline issues with an impossible fluctuating acceleration, but even that would make the alien species visible to the crew.
This episode gets no poem, because someday I’m going to write a story about accelerated living that actually makes sense.