Willing: Thank the moon for life as we know it (column)
September 15, 2017
Editor's note: Find a cited version of this column at http://www.vaildaily.com.
Question: How does a procrastinating, crowd-averse father get his family from Edwards into the path of totality for the 2017 total eclipse? Via Denver and Interstate 24? Heaven forbid. Back roads to Casper? No rooms or campsites for 50 miles in any direction.
Answer: By schlepping northward to Shoshone, Wyoming, and pitching camp in the ersatz Bill's RV Park. A mere sheep pasture until two days earlier, it was now a sheep pasture … with a Port-a-Potty.
For our efforts, we were rewarded with down-home hospitality and front-row seating for one of nature's most stunning spectacles: a total eclipse of the sun.
Now, you may think the moon is quite ordinary. From an astronomical standpoint, nothing could be further from the truth. For starters, our moon is 50 times larger than any other moon in the solar system, compared to its host planet.
Even to have a perfect eclipse is quite remarkable. As luck would have it, the sun is both 400 times larger in diameter than the moon and 400 times farther away, so that the moon can perfectly occlude the sun while allowing us to see and study its corona. Because the moon is slowly pulling away from Earth, in about half a billion years, there will be no more total eclipses. This may seem like a long time — it is, actually — but in geological terms, we're 90 percent there.
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Until quite recently, the origin of the moon was a complete mystery. The prevailing theories during my youth — capture of a floating celestial body or simultaneous formation out of the same cosmic building blocks — were eventually proved impossible. Then came the moon landings. Between 1969 and 1973, the Apollo missions returned more than 800 pounds of lunar material.
The lunar crust exhibited chemistry virtually identical to Earth's mantle, yet was strikingly different from other bodies in the solar system. Chemical analysis and computer modeling led to a startling conclusion: long ago, a celestial body about the size of Mars may have struck the infant Earth.
For the physics to work, it had to be moving relatively slowly and strike the Earth at just the right angle. Too fast, and both are vaporized. Too steep, and it is completely absorbed. Too shallow, and it bounces off like a billiard ball. Most of the object had to be assimilated into the Earth. Our moon would be formed by remnants ejected into space.
Within our solar system, Earth is uniquely conducive to life, and much of that we owe to our silvery moon. The moon's gravity exerts a stabilizing effect on the Earth's spin. Otherwise, it would teeter like a top. So long as the Earth's axis of spin is oriented to its orbit at an angle of 23 degrees, we have a stable, four-season climate in temperate regions with ice confined to the poles, where it belongs. Without that stable axis, life at all would be difficult; advanced intelligent life nearly impossible.
The planet closest to Earth in size and structure is Venus. Yet Venus is clothed in an incredibly dense atmosphere composed of carbon dioxide and sulfur dioxide. The thick atmosphere traps the sun's energy resulting in a runaway greenhouse effect and surface temperatures of almost 900 degrees. As best as we can ascertain, the primitive Earth would have been similar. Something in Earth's early history blew away most of the atmosphere, making life possible. An early collision event would have done exactly that.
Precise measurements reveal that the Earth's rotation is gradually slowing down. Rewinding the clock tells us the early Earth was spinning much faster: one complete rotation every six hours or less, perhaps much less.
At that rotation speed, the Earth's surface water would amass around the equator, completely submerging the temperate regions. Volcanoes and earthquakes would be far more frequent and severe. Advanced civilization would, again, be nearly impossible. We can thank the moon for this. Gravitational friction from the moon slowed the Earth's rotation to a very comfortable 24-hour period.
We may even have to thank the moon for the carbon that is the basis of all life. Under the conditions of the early Earth, most of the carbon should have evaporated into space or sunk to the core. A colliding object of similar composition to Earth may have replenished the mantle with enough carbon for life to exist.
Since the theory took off in the mid-1970s, the evidence for an ancient collision event has become increasingly compelling. There are details to be worked out and mysteries yet to solve, but there is no competing alternative in the astronomical community.
Based on all we have learned, human life and civilization would have been impossible without the benefits provided conferred by our lowly moon. Still, some scientists are concerned that the sole surviving explanation demands far too many "cosmic coincidences." Coincidences? Maybe — maybe not.
Steven J. Willing is an Edwards resident.
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