Why does the moon always face us?

Question

It is just one of those freaks of nature that the rotation of the moon corresponds to its orbit so that it always faces the Earth? It this the same with the moons of the other planets in the solar system?

Answer 1

It just happens, that at this period in time, it's rotation period, ie day, works out that it does appear to face us. Once it almost certainly did not.

Answer 2

it doesn't spin, but I don't know why. I don't know about other moons either, I'm sorry I answered this now.

Answer 3

It's no coincidence, and no freak of nature.

It is because one side of it is more dense, meaning the earth's gravity has more effect on that side.

After millions of years, this slight bias to that side has caused the moon's orbit around the earth to be in sync with its rotation about its axis.

Edit: Why do some questions attract a huge number of thumbs down on all the answers?

Answer 4

What is more amazing all the dark 'Seas' face the earth. If the moon was the other way round it would be much brighter

Answer 5

The invading alian space port is on the other side.

Answer 6

The reason is simply the gravity of Earth - it distorts the moon into a slight egg shape, just like the moon is causing tides on Earth.

This distortion made the moons rotation slow down and become equal to the length of one orbit around Earth, because of Earths gravity being slightly higher at the side pointing towards Earth, than at the opposing side.

Imagine a wheel with a tiny weight on one side. You can give it a strong push and make it spin fast - but finally, it will slow down and the weight will point towards the ground. Nothing else happened with the moon.

It happens everywhere in the solar system, so the mechanism got a special term for describing it: Tidal lock.

Answer 7

darlin'...from every point of view it would face us... I guess...

Answer 8

The Moon rotates about it's axis at the same time as it rotates around the Earth - thus, it's same face is always pointed towards us.

You'll understand what I mean when you watch this next video-clip - it shows the Moon orbiting the Earth but rotating at exactly the same speed as it orbits - thus only ever showing one face to the Earth.

http://www.youtube.com/watch?v=rp7FQXSrm...

More info about the Moon orbiting the Earth which orbits the Sun etc. . . .

http://www.youtube.com/watch?v=2aFGNGEcD...

Moon buggy ride with NASA

http://www.superxm.com/2007/08/amazing-m...

NASA Luna landing July 20th 1969

http://www.youtube.com/watch?v=k_OD2V6fM...

Answer 9

No, our moon is the only one which the same side faces it's host planet all the time.  That's because when the solar system first formed and the earth was still a ball of molten lava, the moon was part of the earth.  We were hit by a giant ball of rock that broke off part of the earth, which formed the moon.  Rocks brought back from the Apollo missions clearly showed the moon was once part of the earth. That's the only way the same side could face us all the time.

Answer 10

because he likes to talk to earh

Answer 11

You're right, the Moon has what's called a synchronous rotation, which means it takes as long to rotate on its axis as it does to make one orbit; and therefore always keeps the same hemisphere pointed at the Earth.

It is not exactly synchronous though, due to something called longitudinal libration. When the Moon is at its perigee (closest orbital point to Earth), its rotation is slower than its orbital motion, and this allows us to see up to eight degrees of longitude of its eastern (right) far side. Conversely, when the Moon reaches its apogee (farthest orbital point from Earth), its rotation is faster than its orbital motion and this reveals eight degrees of longitude of its western (left) far side.

All moons in the solar system have a synchronous orbit, except for Saturn's moon Hyperion, which rotates chaotically because of the gravitational influence of Titan.

Answer 12

Most major moons in the solar system have synchronous rotation due to tidal locking

Answer 13

Some confused answers there.  Did you know the moon (Luna) and Earth rotate around a virtual point some 1,000 miles into the Earth?  And that Luna spins on it's own axis, rotates around us, and we rotate around the sun, Sol.  Even Isaac Newton said that thinking about the Moon's motion gave him a headache.  Yet just last week, it occured to me... The fact it only shows one side to us, is too contrived.  It is unnatural coincidence, by several orders of magnitude, that is should appear stationary to us!  Alien civilisations, aeons older than us, use the 'dark-side' as a base, and can approach the Earth in the blind-spot behind it.  They come for our water and minerals.  That's my theory, anyway.  Now dis-prove it.

Answer 14

Someone just answered this question very well regarding our own moon.  As regards other moons, I don't know of any other planet in our solar system that has this unique feature.

Answer 15

The moon has a tidal bulge in its surface, about 30 miles high I believe, on the side facing Earth. Many billions of years ago, the Moon was not tidally locked - so the tidal bulge did not quite face the Earth (because of inertia) and Earth's gravity had a small but non-zero effect of slowing down the rotation. Incidentally, this effect is currently working the other way around; the Earth's rotation is slowly slowing down. However, the effect of the Moon on the Earth is much less than vice versa, so this hasn't been completed yet. The same effect means that the Moon is also going away from Earth very slowly.

As far as the moons of the other planets are concerned; most of those are tidally locked as well. The only exceptions are the moons of the giant planets that are a long way out. For example, Jupiter has four known moons (last time I checked) that orbit well over 10 million miles away and they are probably not tide-locked. The four Galilean moons (Io, Europa, Ganymede and Callisto) of Jupiter and most of the moons, notably Titan, of Saturn are tide locked.

An interesting case is Neptune's moon Triton. The same effect as described above is happening there; however, for unknown reasons Triton is orbiting in the opposite direction to its rotation (also opposite to the orbits of all the Solar system's moons and to the planetary orbits) and so Triton is gradually spiralling inwards and probably speeding up its rotation as well. This means that at some time (thought to be hundreds of millions of years into the future) Triton will break up and form a rather large ring for Neptune.