And you know what happened. Within a half hour I discovered that the claim was completely bogus. Fortunately I didn’t think young-earth creationism and Christianity stand or fall together, but I worry about Christians who think they do. Eventually they’re going to discover that the arguments for a young earth are invalid and, in many cases, dishonest. It will be very difficult for them to accept the valid arguments for Christianity when the arguments for a young earth don’t stand up to scrutiny.
Anyway, the argument I investigated was based on the amount of meteoritic dust on the Moon. We can measure the amount of dust influx to the Earth, and then estimate how quickly it will accumulate; the higher the rate of influx, the faster the accumulation. We can then measure how much dust has actually accumulated on the Earth and Moon, and determine how long it would take for this amount to be reached.
In the past, young-earth proponents have maintained that the rate of meteoritic dust falling on the Earth and Moon is very high. Henry Morris, in Scientific Creationism, wrote, “The best measurements have been made by Hans Pettersson, who obtained the figure of 14 million tons per year” (his emphasis). The depth of the dust on the Moon’s surface is only a few inches. Therefore, since a lot of dust is falling on the Moon, but only a small amount has actually accumulated, it hasn’t been accumulating very long; ergo, the Moon must be very young.
However, Morris’s claim regarding the rate of influx is not true. Talk Origins has a good essay on this by Chris Stassen, which goes over the historical development of these measurements, and this argument. In the late 1950s, Pettersson went up to the top of Mauna Loa in Hawaii and, with a tool designed to measure smog levels, collected dust settling to the Earth. He measured the amount of nickel in the dust and used this to determine his calculations, since he knew the approximate level of nickel in meteoritic dust. Assuming that all of the nickel was from settling meteoritic dust, he calculated approximately 14 million tons of dust was settling to the Earth per year. Pettersson thought this value was much too high, and suggested that five million tons was a more reasonable figure.
Unfortunately, Pettersson’s assumption that all of the nickel was from settling meteoritic dust was wrong. Wind erosion and, most relevantly for Pettersson’s location, volcanic activity pushes earth-based nickel into the atmosphere where it resettles to Earth. Since Pettersson made his measurements on the top of an active volcano, most of the nickel he measured was earth-based, not from meteoritic dust. By the early 1970s, the amount of meteoritic dust influx had been directly measured by satellites, which set the influx rate to the Earth at about 23,000 tons per year. Additionally, other methods, such as the rate of micro-cratering on objects left exposed on the surface of the Moon and the chemical signatures of ocean sediments set the amount of influx (on the Earth) at between 20,000 and 40,000 tons per year.
Moreover, we can’t simply measure the depth of the dust on the surface of the Moon and translate this into the amount of meteoritic dust accumulation. Stassen argues:
[T]he lunar soil is not the only meteoritic material on the lunar surface. The “soil” is merely the portion of powdery material which is kept loose by micrometeorite impacts. Below it is the regolith, which is a mixture of rock fragments and packed powdery material. The regolith averages about five meters deep on the lunar maria and ten meters on the lunar highlands.
In addition, lunar rocks are broken down by various processes (such as micrometeorite impacts and radiation). Quite a bit of the powdered material (even the loose portion) is not meteoritic in origin.
When all of this is taken into account, the depth of meteoritic dust on the Moon’s surface translates to an approximate age of 4.5 billion years.
All of this information was available in 1974 when Henry Morris referred to Pettersson’s original measurements, an amount which Pettersson himself thought was much too high, as the “best measurements.” Obviously, this argument was rigged by selecting the most extreme measurements, and misrepresenting them as if they were the most reliable. However, and to their credit, it should be noted that although this continues to be one of their most popular and commonly cited arguments among laymen (at least in my experience), some young-earth proponents have conceded that it’s fraudulent, and many (though not all) young-earth ministries have ceased to propound it.