Without the moon, humans wouldn't exist. Life, if it had started at all, would be in its earliest stages of evolution. Days would last four hours, winds would blow at hurricane force and there would be a dense and toxic atmosphere resembling that of Venus. Around 50 million years after the formation of the solar system, a Mars-sized planet called Theia hit the newly formed Proto-Earth. The blast sent planetary material from the pair into orbit around earth which eventually formed the Moon. In this one-hour special, viewers learn what Earth was like before the moon creating impact, and what Earth would have been like if the moon had never existed.