Feature Birth of the Moon   Was our Moon once part of Earth?     The Moon has been circling the Earth for more than four billion years. But where did it come from? Some scientists thought that it was captured by the Earth when it came too close. Others thought that it was once part of the Earth.   Today, most scientists believe it is the 'Earth's child'. It was born when a wandering planet crashed into the young Earth. Huge amounts of material were thrown into space, eventually coming together to form the Moon. This 'big splash' theory would explain why the Moon’s rocks are very similar to those on the Earth.     Unlike the Earth, the Moon seems to be dead inside. Today, there are no volcanic eruptions and any Moonquakes are very small. At its centre is a small, solid iron core. There is no magnetic field, so explorers could not use compasses on the Moon.       Last update: 6 December 2004 - The Moon  •  Moon eclipses (http://www.esa.int/esaKIDSen/SEMQNAWJD1E_OurUniverse_0.html)  •  Moon phases (http://www.esa.int/esaKIDSen/SEMNQ6WJD1E_OurUniverse_0.html)