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> >I read a few weeks ago that the earth was slowing down. I would like
> >to know whether there is an experiment I could do to show what is happening
> >for my physical science class.
Hi Paul,
I don't know if anybody else has answered your question, but I'll give it
a try. The Earth's rotation (spinning) is slowing down because of the
moon's gravity. The moon causes tides in Earth's oceans, because the moon
is pulling the water toward it. (The moon pulls the ground toward it, too,
but the ground cannot move, while water can.) The sloshing of the water
causes friction, which will slow the Earth's spinning down. This will
continue to happen until the Earth's rotational period and the moon's
orbital period are the same - in other words, a day and a month will have
the same length! This process is very slow, however - a few seconds a
century. Scientists have found evidence that, in the distant past, there
were over 400 days a year - caused by a day being only 23 hours long
instead of 24. (I don't understand HOW the paleontologists can figure
this out, though.)
As far as an experiment, I don't know that there is an easy experiment to
do. The problem is that tides are very hard to produce in the laboratory.
Friction is easy enough - slowly lowering a spinning tire wheel onto a
table top will slow the spinning of the wheel.
For more on tides, see the following web site:
http://csep10.phys.utk.edu/astr161/lect/time/tides.html
Sincerely,
Kurtis Williams
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