Dogma on the Rocks
A recent article in the View section featured comments by Bill Hoesch, a graduate geology student at the Institute for Creation Research, which teaches that the Bible is right and Darwin wrong. Hoesch, 32, who hold’s a bachelor’s degree in geology from the University of Colorado, told our interviewer: “I can’t prove that the Earth is 6,000 years old, but (evolutionists) can’t prove it’s 4.5 billion years old.”
Oh?
The evidence for the age of the Earth is based on the known rates at which radioactive elements decay into other elements. The age of a rock can be determined by comparing the amounts of starting products and ending products that it contains.
The oldest known rocks on the planet come from the western coast of Greenland. By using the rate at which rubidium-87 becomes strontium-87, the Greenland rocks have been dated at almost 3.8 billion years old. That means that at least 3.8 billion years ago, the Earth had rocks.
But the Earth was an undifferentiated molten mass before its cooling allowed rocks to form. Radioactive dating can’t go back that far, but the age of the Earth can be estimated indirectly in three ways:
First--The age of meteorites has been determined based on the rate at which uranium becomes lead and rubidium becomes strontium. By these measurements, meteorites were formed 4.6 billion years ago. If meteorites are remnants of the material that formed the planets, the Earth would be 4.6 billion years old.
Second--The dating of rocks from the moon, based on the rate at which potassium becomes argon, puts them at 4.6 billion years old. The surface of the moon solidified early in its history, so its rocks are a good indication of its age. If the Earth and the moon were formed at the same time, the Earth would be 4.6 billion years old.
Third--Some isotopes of lead are formed by the decay of uranium, and some are not. The amount of time that has elapsed since the formation of the Earth can be estimated by comparing the relative abundances of the isotopes of lead on Earth with those in meteors containing no uranium. By this method, the Earth is 4.6 billion years old.
Each of the estimates involves assumptions that may be challenged, but the fact that all three methods of estimating the age of the Earth lead to the same answer adds a certain weight to it.
“It is hard to avoid the conclusion that our planet was formed 4.6 billion years ago,” James Trefil concludes in his forthcoming book, “Meditations at 10,000 Feet” (Scribner’s), from which this discussion of the age of the Earth is taken. Even if the estimate is not exactly right, the Earth is much closer to 4.6 billion years old than it is to 6,000 years old.
Creationists may believe anything they want, and they may teach it to each other if they choose. But these beliefs are held in spite of the evidence, not because of it. And it is patently untrue to assert that neither estimate of the age of the Earth has been proved.
