Factual error: The Earth and the Moon are not in the same phase. The Earth is gibbous, while the Moon is crescent. In the real world, they should be in almost exactly the same phase from every angle of view. (00:01:50)
Factual error: Shortly after Sam finishes speaking to his teenage daughter, he begins to sob. It then shows his moon car and the entire earth in the background. Sam is on the far ("dark") side of the moon, which never faces Earth.
Revealing mistake: In the scenes where Sam 1 and Sam 2 are in touch, the double is completely wrong. Wrong hair, wrong profile and wrong hind end.