January 25, 2012

The Majestic Moon from Mexico


The Majestic Moon from Mexico

I just love the moon. The fact that no matter where you are on earth, you can look up and see it is somewhat comforting. Only at very high latitudes are there times when the moon is not in the sky on any given day, and even there, the moon is up around half the days of every month.

Our moon is the only place that our species has been, other than the earth. 12 people have walked on the moon, all between July 1969 and December 1972. In total, 24 people have been around the far side of the moon, all with the Apollo program.

Some refer to the far side of the moon as the dark side. That is not in fact the case. It is merely the side that is always facing away from us. Some people think the reason why we only see the one side of the moon is because it does not rotate. That is not true. It does in fact rotate, it is just that the length of time it takes to complete one rotation is exactly the same amount of time it takes to complete one orbit: just over 27 days.

This was not always the case. At one point the moon spun much more rapidly, but due to the tidal forces of the earth, its rotation gradually slowed. Tides on earth make sense, the water is pulled by the gravity of the moon to form a bulge, or wave that circles the planet as it rotates. The same thing happened on the moon, except there is no water on the moon, so it was rock that was changing shape. 

This takes an enormous amount of energy to do, so after millions or billions of years, the tidal forces stabilized it the way it is now. The same thing is in fact happening to the earth. Eventually the earth will take the same amount of time to rotate as the moon takes to make an orbit. That would make the moon always appear in the same place in the sky, only visible to half the planet.

This has happened to the dwarf planet Pluto and one of its moons, Charon. It is a bit weird to think about. We shouldn't have to worry , as this will all take a few billion years. I took this photo in 2008 from Mexico.

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