Teaching about Radiometric Dating

Students, particularly Young-Earth Creationists, may come in with misconceptions about how the age of the Earth and of various parts of the fossil record were determined.

• For example, they may assume that the whole geologic timeline is based on radiocarbon dating, which only gives reliable results for dates back to 40,000 years before present (Low, personal communication).
• Others will argue that decay rates could have changed (Wise, 1998 ), or that God could have changed them, which might result in too-old dates.
  • The former argument is flawed because many radiometric dates are broadly supported by other estimates of change, such as tree rings and varved sediments for radiocarbon (with some discrepancies, but still leaving the Earth far more than 6,000 years old).
  • The second is not a scientific argument. If supernatural forces are changing the laws of physics while we're not looking, no form of science, "creation science" or otherwise, can prove or disprove it.
• Students may also be aware that bad assumptions and contamination can result in inaccurate radiometric dates. This is very true! This doesn't change the enormous number of consistent radiometric dates for many of the important events recorded by the Earth system. However, a lesson on sources of error and techniques used to minimize and detect error in dating may be more useful to students in later life than memorizing more dates.
• If students are convinced that our understanding of radioactive decay is completely incorrect, there are certain corollaries they need to consider. For example, our nuclear power, nuclear weapons, nuclear waste, and aircraft carriers are utterly unsafe, as are many labs and hospitals. What are they going to do about that? How has our nuclear technology worked so well for so long?

Resources

• Talkorigins.org Radiometric Dating FAQ (more info) : Detailed essay (with a table of contents) explaining the basics of radiometric dating and refuting misconceptions and creationist arguments on that topic.
• Wise, 1990 : an activity to teach about radiometric dating and decay curves using melting ice.
• Miller, 1999 points out that no radioactive isotope with a half-life of less than 80 million years is found in nature in our solar system except for daughters of other radioactive isotopes and those like C¹⁴ that are being continuously formed by the environment. The table of missing nuclides (radioactive isotopes) is reproduced midway down Evidence for Evolution and an Old Earth: A Catholic Perspective , another Christian evolutionist website, which has a long section on radiometric dating.