What is Selenology?

Selenology is the study of the Moon.






What is the Earth Moon System?

The Erath Moon System represents the system comprising the Earth and the Moon held eighty-one times the mass of the Moon and is at a distance of 384,400 km.

Let us, for example, consider a 1 kg ball and an 81 kg ball connected by a bar. The bar can be balanced at a point nearer the 81 kg ball, so the bar remains horizontal. The pint at which the bar is balanced is called the “Centre of Mass” of the system representing the two balls and the bar.

In the case of the Earth Moon System, the two balls are replaced by the Earth and the Moon and the bar is replaced by the invisible force of gravity which holds them together. The Earth Moon System will remain in equilibrium at the centre of gravity or centre of mass of the system, which will obviously be nearer to the Earth than to the Moon.


What is the gravity on the Moon’s surface?

It is about one sixth of the gravity on the Earth’s surface.

What is the relative mass of Earth with respect to the Moon?

The Earth has 81 times the mass of the Moon.