Argument 5
Young-earth "proof" #5: The Moon is receding a few inches each year. Less than a million years ago the Moon would have been so close that the tides would have drowned everyone twice a day. Less than 2 or 3 million years ago the Moon would have been inside the Roche limit (and thus destroyed). (Dr. Hilpman v. Dr. Hovind, June 15, 1992; the Royal Hall of the University of Missouri)
5. Once again, Dr. Hovind's figures just boggle the mind! Let us assume, for the sake of argument, that the Moon is receding at 6 inches per year. If we go back a million years, then the Moon was 6 million inches closer to the earth. That comes to about 95 miles! Since the Moon is about 240,000 miles away, that doesn't amount to diddly-squat! Indeed, since the Moon doesn't orbit in a perfect circle it varies more than that on its own.
A more accurate estimate, based on the present rate of lunar recession, puts the Moon within the Roche limit around 1 or 2 billion years ago. That is the argument most creationists use. (Since Dr. Hovind's notes match the figures he quoted in his debate with Dr. Hilpman, I assume that those figures are not a simple oversight.)
As I understand it, the tides act as a brake which slows down the earth's rotation. The earth's lost energy can't simply disappear, and it goes into speeding up the Moon. As it speeds up, the Moon moves to a higher orbit. Thus, the energy of the Earth-Moon system is conserved.
The effectiveness of the tidal brake on the earth's rotation strongly
depends on the configuration of the oceans. Thus, we should inquire as
to whether the current arrangement is an average value or not.
The present rate of tidal dissipation is anomalously high because the tidal force is close to a resonance in the response function of the oceans; a more realistic calculation shows that dissipation must have been much smaller in the past and that 4.5 billion years ago the moon was well outside the Roche limit, at a distance of at least thirty-eight earth radii (Hansen 1982; see also Finch 1982). (Brush, 1983, p.78)Thus, our moon was probably never closer than 151,000 miles. A modern astronomy text gives an estimate of 250,000 kilometers (155,000 miles), which agrees very closely with Brush's figure (Chaisson and McMillan, 1993, p.173). Thus, the "problem" disappears!
It may surprise you to learn that Darwin's son, George Darwin, a respected scientist in his time, did some serious calculations along this line. In the nineteenth century that was a reasonable scientific conjecture. Today, in the light of what we know, it's an exercise in futility. For more insight into the problem, see Dalrymple (1991, pp.51- 52).