Wrong radiometric dates, and why they matter
Creationists have long pointed out a major problem with trusting radiometric dating methods: that they are often wrong on dates of known age, so why should we trust them on rocks of unknown age? When biblioskeptics are confronted with this severe evidence, sometimes they try to get out of it by claiming that the dating methods were illegitimate for the age of the sample. One example from the USA follows. Dr Jonathan Sarfati explains the logical fallacy of such a criticism.
I’ve just read Evolution’s Achilles’ Heels. Dr Jim Mason wrote the Chapter on Radiometric Dating. I recently read a book by Dr Jonathan Sarfati. They both cite the Mt Ngauruhoe and Mt St Helens studies to prove K-Ar radiometric dating is inaccurate. The oldest lava from these studies is from 1949. My understanding is that this technique in only accurate from 200k to 5M years. (McDougall & Harrison 1999). Thus, it seems Mason and Sarfati’s conclusions are misleading. Shouldn’t Creation Ministries address the boundaries of K-Ar dating and explain why their conclusion are still correct in view thereof?
I am a Christian, and nothing bothers me more than reading a Christian book that omits or misrepresents facts that are contrary to the Christian teaching being supported. I believe this gives the appearance that Christians are trying to dupe the public into belief. Would you please comment on their conclusions in view of the limitations of K-Ar dating. Please withhold my initials.
Thank you for writing to CMI.
I should point out that it looks part of this is copy-pasted from somewhere, hence the (McDougall & Harrison 1999) which normally indicates a fuller reference in a bibliography list, probably from Wikipedia, which has aptly been called the Abomination which Causes Misinformation. Also your understanding is not correct even from an evolutionary viewpoint—as a rule of thumb, I would expect, if evolutionary assumptions are right, that the technique should be accurate for ages around the half life or a few orders of magnitude away from it, and the half-life is s 1.248 Ga. So K-Ar dating is used for meteorites claimed to be as old as the earth, about 4.5 Ga according to uniformitarian geologists. The Wiki page errs because the reference cited is to a different method: 40Ar/39Ar dating.
But do you understand why radioactive dating methods should have such a range? If the rock’s age is many orders of magnitude less than the half life, then there should be no time for a detectable amount of daughter isotope to have been produced by radioactive decay. On the other side, if the age is many orders of magnitude times the half life, then the parent isotope should have decayed so that the remainder is below detection level.
So the logical argument is: if the assumptions are correct, then a rock younger than the lower range should not have existed long enough for enough detectable Ar-40 (daughter isotope) to have been produced by decay of K-40 (parent isotope). Thus, according to the critic, we should not expect to be able to use the method. However, we find plenty of detectable Ar-40 in rocks known to be much younger. Therefore, by the logically valid argument known as denying the consequent or modus tollens, at least one of the assumptions behind radiometric dating is false: that there was no daughter isotope in the rock to start with.
On the other side of the age range, finding detectable C-14 (parent isotope) in diamond shows that they have not existed long enough for it to have decayed, certainly much less than a million years. So if the diamond really were billions of years old, then C-14 would be an unsuitable dating method to choose. See Diamonds: a creationist’s best friend: Radiocarbon in diamonds: enemy of billions of years.
So the objection is really the fallacy of begging the question: presuming that the assumptions are right, and using that to dismiss observations that show them to be wrong.
In general, Christians have sound biblical reasons for rejecting many radiometric ‘dates’ as well as the scientific ones. Also, Christians at least have an object moral reason to avoid lying: the Creator who owns us has forbidden this. But if we are really rearranged pond scum, as atheistic evolutionists believe, then lying is just a collection of sounds produced by muscles and larynx stimulated by nerves activated by brain chemistry. But the brain chemistry of lying obeys the same laws as the brain chemistry of truth-telling. See the related articles to explain these points further.