Word: moone
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Dates: during 1960-1969
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Strange Discrepancy. That far, the theory is disarmingly simple. But astronomers can calculate the new orbit of such a recent captive, and the moon does not move along the expected path. Instead of curving along an eccentric ellipse far out into space and then close to earth again, the moon moves along a mildly deformed circle. Such a course would be explainable for a satellite that was moving in the opposite direction from the earth's rotation at the time it was captured. But the moon now revolves in the same direction, and to prove his theory correct...
...When the moon was first captured. Dr. Alfven believes, it did indeed curve through space in the opposite direction from the earth's rotation. And, as expected of such a satellite, it drew gradually closer to the earth. Its orbit became circular. About 2.5 billion years ago, the earth-moon system passed through a violent crisis. The approaching moon exerted more and more gravitational pull on the earth's oceans. Tides miles high swept around the globe in a few hours. At last the moon reached Roche's limit,* the closest that a satellite can come...
Buoyant Granite. When the giant meteors stopped falling, and the atmosphere cooled off, the diminished moon, having lost about half its mass, was once more just outside Roche's limit. It was now revolving in the same direction as the earth, and as a result it withdrew slowly to its present distance (240,000 miles...
...theory, Alfven points out that the earth's continents are made of comparatively light granitic rock that floats on the heavy basalt underlying the oceans. The basalt, he says, may be the original earth. But the buoyant granite of the continents has about the same density as the moon and nearly equals the moon's present mass. He suspects that it is moon-stuff that dived to earth through the fiery atmosphere 2.5 billion years...
...Discovered by French Mathematician Edouard Roche in 1850. For the present earth-moon system. Roche's limit is about 9,700 miles from the earth's center. The limit applies to bodies held together principally by gravitation, not to man-made satellites...