The earth's rotation is slowing at a rate of about 0.005 seconds per
year per year. This extrapolates to the earth having a fourteen-hour
day 4.6 billion years ago, which is entirely possible.
The rate at which the earth is slowing today is higher than average
because the present rate of spin is in resonance with the
back-and-forth movement of the oceans.
Fossil rugose corals preserve daily and yearly growth patterns and show
that the day was about 22 hours long 370 million years ago, in
rough agreement with the 22.7 hours predicted from a constant rate of
slowing (Scrutton 1964; Wells 1963).
