There’s an interesting article in August’s Cosmos magazine proposing that Earth’s moon was formed not by a collision between Earth and another large body, but by a runaway nuclear reaction in the D”-layer around the Earth’s core.

The suggestion is that radioactive uranium and thorium sunk down early in the Earth’s history to in the D”-layer, were concentrated there and formed a natural nuclear reactor. This reactor, with nothing to moderate it (like the boron rods used in man made reactors) or to cool the resultant heat (water is generally used in reactors) raised the surrounding temperatures by up to 8000 degrees, forming a giant hot bubble that ruptured the Earth’s surface flinging material into orbit.

A portion of the orbiting material would then have gravitationally aggregated into today’s Moon. The researchers believe that their hypothesis explains some of the anomalies with the mineral and isotopic composition of the Moon better than the existing collision theory. It’s pretty hot stuff!

P.S. I just realised that I am still talking about births and babies – just on a planetary scale!