Sunday, July 29, 2007

Changing Times

The Moon (Lunar eclipse shown left) has been gradually slowing the Earth’s rotation and gradually INCREASING the length of a day on Earth, which could eventually (very eventually) be good news for all those people who "just can't find enough hours in the day."

Some 900 million years ago, an Earth day lasted only EIGHTEEN (18) hours, and an Earth year had 481 calendar days (except there weren't any calanders...a human invention, back then), while some 900 million years from now, at the current rate of change ( appx. 2 seconds every 100,000 years), a single Earth day will be nearly 30 hours long hours and an Earth year will have just 292 days!

This happens due to what scientist call “tidal effect.”

The same side of the moon always faces Earth because the moon rotates on its axis at the same rate as it revolves around the Earth - about once a month. This is called "synchronous rotation".

Long ago, the moon's rotation rate was much faster, but it was slowed down by the tidal effect. The Earth’s gravitational pull caused a "tide" on the moon, in which the part of the moon closest to Earth tended to bulge outward. Over time, the attraction between the Earth and the moon's moving tidal bulge caused its rotation rate to slow down.

The same thing is now happening to the Earth, but much more slowly - attraction between earth tides and the moon is slowing down the Earth's rotation. The Earth’s rotation has been slowed by about 2 seconds every 100,000 years. Eventually, it will match the moon's revolution rate, and about one billion years from now we'll see the 30 hour day and one day in the far distant future one day will become equal in length to a current month. Yikes! 360 hours of daylight followed by 360 hours of darkness...that'd be tough to take.

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