Moon might have formed in five hours

They say Rome wasn’t built in a day, but the Moon might have taken just five hours to form from the debris of a collision between Earth and a Mars-sized space rock. Simulations have tended to focus on the size of proto-Earth and ‘Theia’, the body that evidence suggests once struck our home planet. If Earth and Theia were both hot and smooshy, the chunks that eventually formed the Moon would have stayed largely intact — making it form more quickly — than if the two smashees were cool.