I was recently asked about the creationist “proof” of a young earth that the moon is too close to the earth. Specifically I was asked to comment on the arguments of Dr. Richard Kent, a UK creationist. On his evolution- debunking site he claims:

Observation demonstrates that the Moon is getting farther from the Earth by two inches every year. This indicates that the Moon used to be closer. This causes very serious problems to the Evolutionists, because the proximity of the Moon to planet Earth controls the height of the tides.

Kent's arguments are bad, even for a creationist. It made me wonder if UK creationists are not as experienced or sophisticated as their American counterparts. Kent argues that 4 billion years ago the tides would have been so large that life would not have been possible. However, life was restricted to the ocean until about 500 million years ago – it is not clear by large tides would have been a problem for bacteria living in the ocean. In fact, the high tides were perhaps a boon to ocean life as they scoured the land and deposited minerals into the oceans.

Kent also has this gem:

- The magnetic forces of attraction between the Moon and the Earth become very slightly weaker every year, so that, in general, tides become slightly lower on average.

I love it when cranks get basic scientific facts wrong, because it so clearly exposes their intellectual laziness and scientific illiteracy. The tides are caused by the gravitational forces between the earth and moon, not magnetic forces.

But actually I wonder if Kent is one step ahead of his American counterparts, because Kent is not claiming that 4 billion years ago the moon would have been inside the earth or within the Roche limit (which many creationists falsely claim), but perhaps has tried to rescue this failed argument with his point about the tides being too high. That may be giving him too much credit.

The Institute for Creation Research (ICR) gives the more standard earth-moon argument for why the earth cannot be 4.5 billion years old. They write:

The present speed of recession of the moon is known. If one multiplies this recession speed by the presumed evolutionary age, the moon would be much farther away from the earth than it is, even if it had started from the earth. It could not have been receding for anything like the age demanded by the doctrine of evolution. There is as yet no tenable alternative explanation that will yield an evolutionary age of 4 billion years or more for the moon. Here is as simple a proof as science can provide that the moon is not as old as claimed.

Creationists love the evolution knock-out punches – the one argument or line of evidence that all by itself proves evolution is impossible. Of course, if their argument were true it would present a huge, perhaps fatal, problem for evolution. Interestingly they often simultaneously claim that evolution is not falsifiable – and then they try to falsify it. Evolution is falsifiable, and if any of these killer creationist arguments were true, evolution (or at least certain aspects of it) would be falsified. Alas, they are all silly and/or outdated arguments.

That the ICR and countless other creationist sites are still using the earth-moon distance argument to falsify evolution is also very telling. The argument has been destroyed years ago (during the 1980s and in great detail by the 1990s), but the facts do not seem to get in the way of a good creationist argument. The creationist strategy is clear – find some anomaly that scientists have not yet fully explained and then claim that the anomaly proves evolution is false, or the big bang did not occur, or the sun or moon or earth cannot be billions of years old. Anomalies, however, are not good proofs – they just reveal the fact that our knowledge is incomplete. Scientists treat anomalies as opportunities to deepen our understanding, to great success. Creationists see anomalies as propaganda opportunities, and never let go, even when the anomaly is later explained.

In this case the distance of the moon was a genuine anomaly. The basic facts are this – the moon is moving away from the earth due to the transfer of angular momentum from the earth to the moon as a result of the tidal interaction between the two. At present the moon is moving away by about 2.5 cm per year (there is some debate as to this exact figure that I do not want to get into here). The ICR and other creationists assume (usually without expressly stating that assumption) that the 2.5cm per year figure is constant, and can be extrapolated simply into the past. This turns out to be a false assumption.

The exact manner in which the earth transfers momentum to the moon as a result of the tidal interaction is actually fairly complex. It is affected by the surface features on the earth. Depending upon how you model the earth the calculation can be dramatically different. Initial figures, in fact, produced an age of the earth-moon system that was far too great. But then later revisions came out with an upper limit of 1-2 billion years – short of the needed 4.5 billion years. Creationists latched onto this historical state of the evolution of our understanding of the tidal forces on the earth moon system, because it served their purpose, and then they stopped updating their arguments as the science progressed.

The turning point came with the discovery of plate tectonics – the continents on the earth were not always where they are now. In fact for much of the history of the earth all the land mass was joined in one supercontinent or another. This dramatically affects the calculations for momentum transfer. Modern calculations, with better models of the earth and the earth-moon interaction, now agree with a 4.5 billion year old earth. Anomaly solved. Talk origins has a thorough discussion of the history of this calculation.

This information is now freely available, for more than a decade. The creationist argument was always thin, little more than anomaly hunting and denial. But now it is also outdated. The fact that they do not acknowledge the actual science and they stick to their simplistic and wrong models tells us everything we need to know about the scientific and intellectual integrity of creationism.