Factual error: The astronauts land on an asteroid said to orbit a binary star 655 million miles from Earth. This is impossible, as that distance would place them well within our solar system. In fact, they'd be inside the orbit of Saturn, where of course there aren't (nor could there be) any extraneous suns. The nearest star to our system is, in fact, trillions (not millions) of miles away. (00:02:15 - 00:04:00)
Factual error: Cook draws his sun and planets in the sand, saying that it's "my galaxy." When Norda draws hers, he calls it another galaxy. Wrong. He's drawn a solar system, not a galaxy. (A galaxy is a collection of millions of solar systems.) The terms are in no way synonymous - there's a vast difference, and a trained astronaut would definitely know that. Their little ships can't possibly cross galactic voids (that would require tens of thousands of years, even at many times the speed of light), so Cook and Norda's planets are in different star systems in the same galaxy - this one. (00:16:30)
Factual error: Author Damon Knight was happy with Rod Serling's TV adaptation of his short story - except for the change that allowed the humans to translate the Kanamit language as though it were a code. Said Knight, "Without some sort of interplanetary Rosetta Stone, deciphering an unknown language would be impossible." (00:22:10)
Factual error: The colonists' planet has twin suns and, we're told, no night. We see the suns, side-by-side in the sky. But twin suns would not create perpetual day. Night/day is caused by the rotation of the planet on its axis, regardless the number of suns. In a binary star system, the two stars orbit each other around a central point in space. The planets would orbit around that central point too. In order for there to be no night, the planet would have to pass between the two stars, a process it would not survive. The gravitational forces of two opposing suns would tear the planet apart. (00:18:35)
Factual error: As well as the obvious problem with translating an unknown language as if it was a code, there is no chance that the word "serve" would have the same double meaning in English and Kanamit. It would be like the word "dope" and its French equivalent meaning "idiot" and "illegal drugs" in both languages.
Factual error: Throughout this episode, the TV western supposedly being filmed lacks several essential elements. There are no clapboards to mark the scenes; the modern-day car is constantly in shot through the swinging doors; and the set is located inside the "real" saloon when it should be on a sound stage.
Factual error: When they looked at Mr. Herbie's case, they only saw the skeleton. Problem is the clothing was missing, where there should have been some remnants. And the vehicle started with no trouble. After a hundred years, the battery should have been dead, and the engine inoperable.
Factual error: Though this episode is set in then-present-day 1961, the fistful of prop money the bartender is holding is not contemporary. It appears to be copies of 1880s U.S. Currency, though it's been reproduced as smaller, 20th Century sized bills rather than the larger ones that were standard in the 1800s. All in all, not something his bar patrons would likely be paying the bartender with in the 1960s. (00:16:40)
Factual error: When all 5 prisoners stand on each other's shoulders with the ballerina on top, she still can't reach the edge of the cylinder. But when just the 4 men do the same thing and the major throws his rope over the edge, he is somehow far closer to the top than he should be. He ought to be the ballerina's height and then some away - but he isn't. (00:21:30)
Factual error: Corey is in solitary confinement on an asteroid. However, asteroids are neither large enough nor stable enough to hold an atmosphere. In addition, the distance from earth stated in the episode wouldn't be much further than the moon; there are no asteroids in a stable, regular orbit around the the moon or the earth, nor around the sun anywhere that close to earth.