Tuesday, August 25, 2009
"The Day the Moon Was Gone": The Universe, History Channel
Tuesday August 25 the History Channel aired “The Universe” episode “The Day the Moon Was Gone.”
As NatGeo’s “Alien Planets” covered, the Moon was created about 4-1/2 billion years ago by a collision with a smaller planet originally at the Lagrange point in Earth’s orbit.
The Moon gradually retreated to its present distance of 234000 miles, and it still retreats slowly.
The Moon has a stabilizing effect on the Earth’s tilt and precession, much the way a high-wire walker uses a pole. The Moon slows down the Earth’s rotation, making the climate more stable. The Moon stabilizes the magnetic field and encourages plate tectonics on Earth, all of which favored a more slowly changing climate that eventually allowed complex life to form. Without the Moon, tides would be much stronger and so would hurricanes. Sea level would be much higher, and the amount of land surface might be much less.
Around other stars, Earth-like planets without a large Moon may be common, and they may be completely covered by ocean. Mars lost its magnetic field and much of its atmosphere and the chance for plate tectonics (and probably its water) because it does not have a large moon.
Attribution link for NASA picture of moon craters http://en.wikipedia.org/wiki/File:Moon-craters.jpg