Classical mythology presented the Moon as the sibling of the Sun. But scientists, having performed an analysis of lunar rocks, are increasingly of the view that our closest neighbour in space is a cousin of the Earth. They believe that a massive chunk of our planet became separated about 4.5 billion years ago and ended up orbiting us – although how this happened scientists are still unsure.
But if the Moon and the Earth were once united, perhaps this will change how we regard our nearest natural satellite.
Mankind has projected all kinds of things on to the Moon over the centuries. Westerners have seen a man in it. In the East, they see a woman. Some think it is made of cheese; others that it is home to a giant rabbit.
Some tribes have associated the Moon with fertility. According to fables, it gives us werewolves. Moons can be blue, or "bad". They have a dark side, too. But if the Moon turns out to be simply a big, displaced chunk of the Earth, will we be able to continue to let our imaginations run wild in the same way?
And what about walking on the Moon? In 1969, the first step of the American astronaut Neil Armstrong was hailed as a giant leap for mankind. But when our species is next up there, perhaps it will feel like going home.