The most accepted modern theory of the existence of the moon states that a giant body struck the Earth and this subsequently created the Moon. A new paper published yesterday however by Sarah Stewart and Matija Cuk argues against this theory.
The scientists claim that their theory better explains why the Earth and the Moon have a similar composition and chemistry. The Earth was spinning much faster at the time the Moon was formed, and a day would only have lasted two to three hours.
Their explanation published on a Harvard Website explains that with the Earth spinning so fast, a giant impact could have launched enough of the Earth's material to form the moon.
They say: “Therefore, the original giant impact model has a major problem: it can match the mass of the Moon and the rotation rates of the Earth and Moon, but not the chemistry of the Moon. Today, tides between the Earth and Moon slow Earth’s rotation and push the Moon’s orbit further away, but the total angular momentum (see glossary) is conserved. Going back in time, the early Earth had a day of only 5 hours when the Moon formed. With a post-impact spin period of about 5 hours, a giant impact could not loft enough Earth material into orbit to make the Moon match the chemistry of the Earth.
Ćuk and Stewart show that if Earth’s initial angular momentum were higher, corresponding to an Earth day between 2 and 3 hours, a giant impact can eject enough Earth material into orbit to make a Moon with the same isotopic fingerprint. A day of only 2 hours is near the point when the Earth would begin to fly apart from rotational forces. When the Earth is spinning near this rotation limit, it is much easier to launch Earth material into orbit during a giant impact.”
Their new theory states that the Earth reached its current rate of movement through a gravitational interaction between its orbit around the Sun and the Moon's orbit around the Earth.
If you want to study their theory then head over to this page, it is interesting reading.
Kitguru says: Will it ever be proved exactly how the Moon was formed?