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Political History What is a Libertarian Democrats Left Liberal Republican History Links |
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Is Earth Slowing Down Creationism Id Intelligent Design
First an absurd AssertionSome prominent creation scientists promote the idea that the Earth's rotational speed can show proof the earth could not possibly be 4.5 billion years old. Their argument goes along these lines. The speed with which the earth rotates on its axis is slowing. Each day, the time required for for the earth to rotate one complete turn on it axis is increasing 1.5 milliseconds. This may not seem like much. But it amounts to over six seconds per decade. Astronomers must insert leap seconds many times each decade to compensate for this slowing. If the earth's rate of deceleration has been constant throughout the life of the earth, then its rotational speed would have been very high 4.5 billion years ago. A day would be have been only a few seconds long. This high rotational speed would have long ago flattened into the shape of a pancake. 11 That clearly did not happen, so the age of the earth must be a very small fraction of 4.5 billion years. Is the Rotation really SlowingTheir basic belief is wrong: the time taken for the earth to rotate on its axis is slowing down by only about 1.5 milliseconds per century -- not per day. The Moon raises tides in the ocean. This generates friction between the sea and the earth, diminishing the earth's speed of rotation. "This effect causes a slowing of the Earth's rotational speed resulting in a lengthening of the day by about 0.0015 to 0.0020 seconds per day per century." 12 The insertion of a leap second in most years is not directly related to this deceleration. In fact, if the earth stopped decelerating and achieved a constant speed, there would still be a need to insert leap seconds in most years. The need for leap seconds is caused by our basic definition of time, which is currently derived from atomic clocks. The second has been defined to match the day as it was in the year 1900. Over a century has passed since that time. During that century, each day has lengthened by about 1.8 milliseconds. So, over a year, the difference between an atomic clock and the earth is about 365 x 0.18 = 657 milliseconds, or 0.66 seconds. Thus the need for the leap second in most years. A century from now, the accumulated error will be over a second each year, requiring two leap seconds in some years.
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