Sunday, November 29, 2009


Oh! Moon with a beautiful face.
Caring thought the boundaries of space.
When I look at you, I think in my mind.
Shall I ever, oh! Ever behold thy behind.


Those who know about the far side of moon, knows what this quote is about! Far side of the moon is the side that we never get to see. Earth is facing only one side of moon. When I tell anyone about it, most of the people don’t believe me. Infact this is true! We always see one side. It was a little sad and abstract to me too when, I first read about it in Patrick Moore’s book when I was in 8th grade or around.

I have noticed that the black spots on moon are always in same fashion, many of you might have also noticed it too.

Tidal forces between Earth and Moon have slowed moon's rotation in a way that one side is always facing the Earth. Whilst the other face, which is never visible from the Earth in its entirety (only 18% is visible under some conditions).

You must be thinking if the same side of the moon is always facing earth then it is not rotating around its own axis at all.

The Moon does actually rotate on its axis; it's just that the amount of time it takes to make a complete orbit around the Earth matches the amount of time it takes to complete one rotation. In both cases, this is 27.3 days (approximately)

The gravitational forces between Earth and Moon cause the interesting effect.

Over the few billions years since its formation, the Moon has become tidally locked with the Earth. In the distant past, the Moon had different rotation and orbital speeds, and it showed all of its sides to our planet. But the gravity of the Earth tugged at the irregular shapes on the Moon, causing it to slow its rotation until it was exactly the same length as its orbit.

The Earth, on the other hand, has so much mass that the force of gravity from the Moon pulling on Earth can't overcome its rotational speed. The Moon does create the tides, though, and causes the ground to rise and fall (its negligible you can’t feel it but it is there)

The far hemisphere was first photographed by the Soviet Luna 3 probe in 1959 and was first directly observed by human eyes when the Apollo 8 mission orbited the Moon in 1968.

The far side of the Moon is shielded from radio transmissions from the Earth; it is considered a good location for placing radio telescopes for use by astronomers.

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