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> We Only Ever See One Side Of The Moon
Steve101
Posted: Feb 6 2012, 01:47 PM


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Anyone know if there is a reason for why we always see the same side of the moon?

I did think that all planets etc rotate on their own axis, but it continues to bother me that the moon rotates at exactly the right speed so that the same side faces Earth. It seem so improbable that I wonder if there is something that makes it do that. For example the shape of the moon and the gravitational pull of the earth or something. Or maybe its not exactly the same and in 100,000 years it will show a different side?
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synthsin75
Posted: Feb 6 2012, 05:00 PM


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Robittybob1
Posted: Feb 6 2012, 07:00 PM


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QUOTE (Steve101 @ Feb 6 2012, 01:47 PM)
Anyone know if there is a reason for why we always see the same side of the moon?

I did think that all planets etc rotate on their own axis, but it continues to bother me that the moon rotates at exactly the right speed so that the same side faces Earth. It seem so improbable that I wonder if there is something that makes it do that. For example the shape of the moon and the gravitational pull of the earth or something. Or maybe its not exactly the same and in 100,000 years it will show a different side?

Here's how I see it happening.

When the Moon was first captured by the Earth's atmosphere the Moon would have been rotating faster than the Earth. Tidal effects on the Moons mantle converted the kinetic energy of rotation to just heat, the core of the Moon heated and partially melted and separated. As the rotation slowed the molten core began solidifying in the off-center position and hence has become tidally locked.
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candy183
Posted: Feb 8 2012, 02:55 AM


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Tidal effects on the Moons mantle converted the kinetic energy of rotation to just heat, the core of the Moon heated and partially melted and separated.
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fishspawned
Posted: Feb 8 2012, 03:49 AM


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QUOTE
http://en.wikipedia.org/wiki/Tidal_locking



this is amazing, i'm shocked i never heard of this before. more so in that it makes perfect sense.
thank you.

This post has been edited by fishspawned on Feb 8 2012, 03:50 AM
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Robittybob1
Posted: Feb 8 2012, 04:11 AM


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QUOTE (fishspawned @ Feb 8 2012, 03:49 AM)


this is amazing, i'm shocked i never heard of this before. more so in that it makes perfect sense.
thank you.

In the link it says
QUOTE

Orbital changes
If rotational frequency is larger than orbital frequency, a small torque counteracting the rotation arises, eventually locking the frequencies (situation depicted in green)The angular momentum of the whole A-B system is conserved in this process, so that when B slows down and loses rotational angular momentum, its orbital angular momentum is boosted by a similar amount (there are also some smaller effects on A's rotation). This results in a raising of B's orbit about A in tandem with its rotational slowdown. For the other case where B starts off rotating too slowly, tidal locking both speeds up its rotation, and lowers its orbit.


From other reading the momentum is only partially conserved. A fair amount of the energy and momentum is lost as heat. Without the loss of Kinetic Energy the moon would just keep on rotating.
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El_Machinae
Posted: Feb 19 2012, 07:42 PM


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I love it when people notice something weird, go try to find out why, and then discover the answer.

Curiosity and science are awesome.


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