Corrected entry: Just before his death, Dr. Morbius tells Cmdr. Adams that they must be 100 million miles away in 24 hours to be safe. By my calculations, they'd have to travel at 4,166,666 MPH to get that far away in the time allowed. Kinda makes light speed seem like child's play.
Corrected entry: When the id monster is melting the protective door and parts of the molten door starts to fall to the floor, you can see a person through the resulting holes who is moving around and presumably pushing parts of the door to make them fall through. This happens about 5-10 minutes from the end of the film.