Millions of years after mankind raised various species and sent them to the stars, one of the
species returns and believes that humans have fallen into a primitive existence. And the time
travel? Partway through the story, there’s a power source that goes to the end of time and
cycles back to the beginning of time. In addition, Fred Galvin pointed out to me that even
though it takes the aliens six years to travel to Earth, when they return to their home
planet, only one year has passed, apparently a complete undoing by Seun of Rhth of the alien
invasion.
The story also appeared in Healy and McComas’s seminal anthology, Adventures
in Time and Space, and it was made into a one-act play in 1943 by Wayne Gordon.
In the first revolution it made, the first day it was built, it circled to the ultimate
end of time and the universe, and back to the day it was built.
1 English variant