Bad Astronomy: Misconceptions and Misuses Revealed, from ...

192 ARTIFICIAL INTELLIGENCE
But, again, the creationists are wrong. DeYoung assumed that
you could simply extrapolate the Moon’s current recession rate
backwards in time all the way to when it was formed. As usual in
the universe, things are more complicated than that. The current
rate is actually much higher than usual. The rate depends on how
well the Moon interacts gravitationally with the Earth.
The Earth and the Moon interact like a complicated mechanical
watch, full of gears; if one slows down, they are all affected. So
it is with the Earth and the Moon. The Moon’s gravity moves water
around on the Earth, causing the tides. This water rubs against the
ocean floor, generating friction. That friction takes energy away
from the Earth, slowing its rotation, and gives it to the Moon in
the form of orbital energy. When the orbital energy of an object is
increased, it moves into a higher orbit, so the Moon moves away
from the Earth. The increased distance also means the Moon’s
orbital speed slows.
At this point in history, the Moon’s orbit and the Earth’s rotation
collude to generate a lot of friction with the sea floor, especially
near the shorelines of the continents. An unusually large
amount of energy is being taken out of the Moon’s orbit, causing
it to recede faster than it normally would. In a sense, the Moon’s
gravity has a better grip on the Earth now than it did in the past,
and is better at losing its own orbital energy.
What this means is that you cannot say that the current rate of
4 centimeter per year is a good average. In the past, the rate was
actually slower than this, making the Moon older. DeYoung’s estimate
of an upper limit to the Earth’s age actually turns out in reality
to be a lower limit, and in fact is perfectly in concordance with
an age of the Earth and the Moon of 4.5 billion years.
PPP
Beyond our Earth, the creationists see our very system of planets
itself as an indication of the Earth’s relative youth.
Astronomers have a pretty good idea about how and when the
solar system formed. There have been many theories over the centuries,
but repeated observations have indicated that the solar system
formed about 4.5 billion years ago (which dovetails nicely with
the age of the Earth/Moon system as well). Initially, the solar sys-