“Tomorrow Was Yesterday” was the first Star Trek story David Gerrold pitched to the then-new science-fiction series in 1966. It was inspired by Robert A. Heinlein’s “Universe” and “Common Sense” (both 1941) and bears a similarity to the 1982 French graphic novel Le Transperceneige, which was made into a movie, Snowpiercer, in 2013.
Dave Eversole of Orion Press shared the following synopsis.
The Voyager, a generation ship, one whose slow sub-light speed would take it thousands of years (and several generations of inhabitants) to cross the gulfs of space, was launched hundreds of years ago with human colonists on board. The Enterprise discovers it drifting through space, being drawn inexorably toward a star and certain doom.
After all this time, the colonists have forgotten they are on a spaceship. The interior of the ship is the totality of their universe. A long-ago mutiny divided the colonists into two camps. The elite “lightmen” from the “upper” levels (the spherical ship created artificial gravity by spinning, producing centrifugal forces, thus “upper” refers to the central interior of the ship and “lower” refers to areas near the hull) are descendants of the victors in the failed mutiny. They consider themselves the “chosen ones” and live in the best part of the vessel near the control room. The downtrodden, poorer people — the “demons” — are descendants of the mutineers and scrabble out a meager existence in the lower areas. Both sides conduct periodic raids against each other.
The lightmen have charge of the control room. The demons have control of the eight nuclear power plants which power the ship. Kirk must bring the two sides together before Voyager is drawn into the gravity of the star, but each side believes the boarding party from the Enterprise are enemy spies.
The first hour of the story involves the Enterprise crew being chased, captured and interrogated by both sides.
The second part involves Kirk’s solution to the problem.
McCoy is welcomed by the demons in the lower levels because of his medical aid to their children. Kirk uses this to his advantage and tries to talk the leader in this darkened area into reactivating the lights. The lower-level people have lived in darkness for many years. The dark provides them a level of protection from the lightmen because they can’t see well enough to raid in the dark. Kirk’s plan is rebuffed.
Spock offers another suggestion. He has observed that the ship’s librarian — Specks — wears glasses. He suggests that eyewear be fabricated for the Enterprise crew and the accompanying party of raiders who wish to retake the control room from the lightmen. They will turn the ship’s lights up so bright that everyone will be temporarily blinded — except for those wearing the glasses.
It is done, and Kirk and his crew restart the power plants, storm the control room and capture it. There, they reset the ship’s course and Voyager flies past the star.
The two elderly leaders of the lightmen and demons are removed from power and younger, saner heads are put into their positions.
According to Eversole, Producer Gene L. Coon liked the idea but rejected it because he felt it was too elaborate for television.
He did encourage Gerrold to pitch more ideas, which he did. One became the famous episode “The Trouble with Tribbles”.
Gerrold also turned the outline of “Tomorrow Was Yesterday” into a motion-picture script but failed to sell it. He then adapted the story as a novel, with original characters, which was published as Yesterday’s Children in 1972. He revisited the idea again in a Star Trek novel, The Galactic Whirpool, published in 1980.
“For the World Is Hollow and I Have Touched the Sky”, written by Hendrik Vollaerts, borrows some of the elements of “Tomorrow Was Yesterday”. In the episode, a generation ship disguised as an asteroid is about to hit a Federation world. The people on board don’t realize they’re on a spaceship either.