The Slowing of the Earth's Rotation Rate Means the Earth Must be Young
The argument goes like this, "The Earth's rate of rotation is slowly but measurably declining. Based on this, if the earth were created 4.5 billion years ago, it would be spinning too fast and would have cooled into the shape of a giant bulge at the equator"
Young earth creationists use all kinds of wild numbers for the slowing of the earth rotation period, up to 1 second/year. Let's look at the actual numbers and do the calculation. Presently, the earth’s rotation is slowing down 0.005 seconds per year per year.1 This rate of 0.005 seconds per year per year would, if rolled back 4.55 billion years, yield a 14-hour day.2 Most scientists believe that the earth's rotation rate was originally an 8-hour day. Since the moon was much closer to the earth at its creation, its tidal effects would have been much stronger, slowing the earth more then than now. Likewise, the tidal effects of the earth (which are much stronger that that of the moon because of its larger mass) have slowed the moon's rotation period to 29.5 days. A rotation rate of 8 hours would not cause a huge bulge at the Earth's equator. Even if the rate were much higher, any bulge formed at that time would have disappeared within the last 4.5 billion years due to tectonic activity.
Errors: Invalid assumptions, faulty data
References 
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Thwaites, William and Frank Awbrey. 1982. "As the World Turns: Can Creationists Keep Time?" Creation/Evolution, Issue IX (Summer 1982), pp.18-22 National Center for Science Education, P.O. Box 9477, Berkeley, CA
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0.005 sec/year x 4,500,000,000 year = 22,500,000 sec/year additional at
creation of earth.
Additional days = 22,500,000 sec/year x 1 day/24 hour x 1 hour/60 min x 1 min/60 sec = 260 additional days/year
Earth's Revolution rate = 365.25 day/year x 24 hours/day = 8766 hours/year
Length of day at creation = (8766 hours/year)/(365 + 260 day/year) = 14.02 hours/day
Last updated March 31, 2008
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