Question: "How does radiometric dating fit with the view of a young earth?"

Answer: Radiometric dating does not fit with the “young-earth” view. Radiometric dating is a method that scientists use to determine the age of various specimens, mainly inorganic matter (rocks, etc.), though there is one radiometric dating technique, radiocarbon dating, which is used to date organic specimens.

How do these dating techniques work? Basically, scientists take advantage of a natural process by which unstable radioactive “parent” isotopes decay into stable “daughter” isotopes spontaneously over time. Uranium-238 (U238), for example, is an unstable radioactive isotope that decays into Lead-206 (Pb206) naturally over time (it goes through 13 unstable intermediate stages before it finally stabilizes into Pb206). In this case, U238 is the “parent,” and Pb206 is the “daughter.”

Scientists begin by measuring how long it takes for a parent isotope to decay into a daughter isotope. In this particular case, it takes 4,460,000,000 years for half of a sample of U238 to decay into Pb206. It takes another 4,460,000,000 years for half of the remaining sample to decay into Pb206 and then another 4,460,000,000 years for half of what’s then left to decay, and so on. The time it takes for half of a sample to decay is called a “half-life.”

By measuring radioactive half-lives, by measuring how much parent and daughter are present in any given specimen, and by making certain key assumptions, scientists believe they are able to accurately determine the age of a specimen. The measurements involved can be quite accurate. The questions are, what are the underlying key assumptions, and how reliable are they?

The three key underlying assumptions in radiometric dating are 1) the rate of decay of parent into daughter has remained constant throughout the unobservable past; 2) the specimen being examined hasn’t been contaminated in any way (that is, no parent or daughter has been added or taken away at any point during the unobservable past); and 3) we can determine how much parent and daughter were present at the beginning of the decay process—not all of the Pb206 present today necessarily came from decaying U238; Pb206 may have been part of the original constitution of the specimen. If any of these assumptions are wrong, the method cannot accurately determine the age of a specimen.

The second and third assumptions behind this technique have always been a bit troublesome. This is especially true of the third assumption, which involves the original constitution of a particular specimen. The first assumption was thought to be a safe bet, since scientists were not able to vary the decay rates much in a lab. Recently, however, new research has revealed that the decay rates may have been drastically different in the unobservable past. This, in truth, opens room for doubt concerning the entire method.

Despite those potential sources of error, radiometric dating is widely used by geologists, paleontologists, and archaeologists. These scientists are aware of the potential drawbacks but also find that radiometric dating is repeatable and consistent, even across radiometric methods. In other words, “it works” for the purposes for which those scientists need it to “work.” It should be noted that this drive for practical results, itself, is not connected to any philosophical view of the age of the earth or evolution or religion. That this system might be grossly in error is a possibility these scholars consider, but only as a remote possibility.

Radiometric dating, like any other technique, is not infallible. Nor is it beyond the need for more research and improvement. As with any human effort, it should be used to enhance our knowledge but not relied on as a perfect test of any truth.