Earth's Slowing Rotation

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The rotational speed of the earth (about 1,040.421 mph) is gradually slowing down on account of the gravitational drag forces of the sun and moon along with other factors. If the earth were really billions of years old, as claimed, it should already be in tidal lock with the sun.

Lord Kelvin (the 19th-century physicist who introduced the Kelvin temperature scale) used this slowing rotation as a reason why the earth could not be very old. He calculated that had the earth existed for 7.2 billion years, its rotational speed would have been twice the present speed. This would have produced a difference of 86 kilometers between the equatorial and polar radii of the earth. The actual equatorial radius is 6,378.135 km, and its polar radius 6,356.75 km, a difference of 21 km, not 861.

The decline in rotation rate is now known to be greater than previously thought. If the earth had existed for 5 billion years, then the difference between polar and equatorial radii would still have been significantly greater (64 km) than it actually is. Furthermore, the continents would have been distributed in the tropical regions, and the world's oceans would have collected in the temperate and polar regions. This is a distribution that Kelvin also would have predicted, and he cited the lack of such a finding as a falsification of a great age of the earth2. Thus by either Lord Kelvin's original calculation or a more modern one, the earth cannot be more than a few thousand years old3.(4)

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