Wednesday, February 07, 2007

The Moon's fate

This article talks about the possible demise of both the Earth and the Moon in a very distant future, some 5 billion years from now, when the Sun will have run out of fuel and will swell up into a red giant, encompassing most or all the rocky planets before exploding or imploding.

It's a very interesting article, and the theories of what will happen are fascinating, but I was mostly amazed by this:
The Moon is now moving away from Earth and by then will be in an orbit that's about 40 percent larger than today.
[...]
Today, the Moon is on average 239,000 miles (385,000 kilometers) away.
[...]
The Moon is being pushed away from Earth by 1.6 inches (4 centimeters) per year and our planet's rotation is slowing.
[...]
The drag caused by the Sun's extended atmosphere will cause the Moon's orbit to decay. The Moon will swing ever closer to Earth until it reaches a point 11,470 miles (18,470 kilometers) above our planet, a point termed the Roche limit.

'Reaching the Roche limit means that the gravity holding it [the Moon] together is weaker than the tidal forces acting to pull it apart,' Willson said.

The Moon will be torn to pieces and every crater, mountain, valley, footprint and flag will be scattered to form a spectacular 23,000-mile-diameter (37,000-kilometer) Saturn-like ring of debris above Earth's equator.
Extraordinary.

Imagine how much bigger the Moon will look to those still alive when our satellite is over 20 times closer to the planet. Immense. There would probably be no more "night" at all, since the sun's light reflected off the Moon's surface would be so strong, night would look like day.

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