The Science of Game of Thrones is explained by the concepts of paralleled universes and divergent timelines. Soon after the end of the Pleistocene Epoch in the parallel universe that is the Game of Thrones universe, a comet impacted with the Moon. The impact subsequently led to a meteor shower of large pieces of the Moon bombarding the surface of the Earth. The meteor shower drastically altered the geography of the planet. Although the comet impact did not completely shatter the Moon, it did destroy enough of the Earth's satellite to significantly decrease its size.