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How the Moon was Born
| Article
# : |
11543 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
10 / 1986 |
3,700 Words |
| Author
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Patrick Huyghe
Patrick Huyghe is a science journalist and producer currently
working for Innovation, a science series, on WNET, the public
television affiliate for the New York metropolitan area. |
Long, long ago, a nearby planet shadowed the Earth in its revolutions around the Sun. Perhaps a kind of celestial ballet ensued with this Mars-sized companion, their orbits crossing in reckless celebration of the then-recent birth of the solar system some 4.5 billion years ago. But within a few million years the engagement ended: it seems that the inner solar system just wasn't big enough for everybody. This extra planet created instabilities in the solar neighborhood, and before long the paths of Earth and its ancient partner met in a spectacular collision.
More like billiards than ballet, the mystery planet struck the still largely molten Earth at a speed greater than 20,000 miles an hour. The impact created tremendous temperatures and pressures, and vaporized large portions of the surface of both the Earth and the other planet. Some of the foreign matter, both solid and gaseous, mixed with the Earth as it reformed. The rest of the material was discharged into space, where it formed a thick belt of glowing matter around the Earth. It all happened in less than an hour, but hundreds of years later, this orbiting matter clumped together and formed our Moon. At a distance six times closer than it is today, that huge bright disc was a very formidable presence in the Earth's ancient sky.
This is not a scenario from the latest Hollywood blockbuster movie. George Lucas is not the producer. It is a theory that has gained favor and credibility among scientists, thanks, in part, to a number of recent computer simulations. "I would say there is now a consensus," says Alan Boss, a physicist in the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. "So far we have found no fatal flaws in the hypothesis."
Fantastic notions about the Moon and its origin are not new. The Babylonians, the great astronomers of antiquity, believed that the Earth was the child of the Moon, which they worshiped as the queen of the night. Thousands of years later, evolutionist Charles Darwin's grandson, George, proposed that it had happened just the other way around. He speculated in 1880 that the early Earth was largely fluid and spun so rapidly that eventually a part of it bulged outward and broke off. In the decades that followed, other theories arose, and by the 1960s scientists hoped that the U.S. Apollo manned Moon landings finally would put to rest the question of the Moon's origin. To find the answer became one of the Apollo program's primary scientific goals.
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