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Could radiometric results be cherry-picked?

This post is more than 6 years old.

Posted at 09:00 on 28 August 2017

Radiometric dating deniers like to portray results far in excess of six thousand years as just "rationalisations" or "just-so stories."

Take, for example, this article on creation.com, which claims that "long-age geologists" just disregard (or "reinterpret") any data that doesn't fit their preconceived notions. The author, Tas Walker, correctly points out that radiometric dating doesn't always give the results we'd expect, and that when this happens, scientists come up with an alternative, explanation for the results. He gives some examples of such explanations: heating events since the rocks cooled; xenocrysts; contamination; inherited ages; and so on.

But then he says this:

No matter what the radiometric date turned out to be, our geologist would always be able to ‘interpret’ it. He would simply change his assumptions about the history of the rock to explain the result in a plausible way. G. Wasserburg, who received the 1986 Crafoord Prize in Geosciences, said, ‘There are no bad chronometers, only bad interpretations of them!’ In fact, there is a whole range of standard explanations that geologists use to ‘interpret’ radiometric dating results.

This caricature is very misleading. As we have seen, geologists do not just look for a plausible sounding interpretation based on changing assumptions; they have to rigorously demonstrate which interpretations are consistent with the data and which ones are not. In fact, they can often discover a whole lot of other useful information about the rock strata than just their age — information such as their thermal history, for example. They most certainly are not just a case of making up excuses, or of choosing whichever interpretation you like in order to get the results that you want, and it is quite frankly dishonest to portray them as if they were.

What about unpublished results?

In any case, this caricature does not explain why up to 95% of results do not require any such "rationalisation" or "changing assumptions." To accommodate this high degree of concordance, radiometric deniers instead sometimes claim that discordant results tend to be thrown out, or filed away in a drawer somewhere. But could this be happening often enough to undermine the credibility of radiometric dating?

If it is, the amount of data that they must be withholding is colossal. This article gives some calculations that show that merely to get meaningful isochron plots from random data (remember, isochron dating requires all the points to lie on a straight line) you would have to be throwing away several hundred results for every one that you accept. It gives a couple of examples of single isochrons from the scientific literature that would have cost as much as $1.7 million if they really had been the result of cherry-picking random numbers.

But let's suppose that all isochron plots are all due to mixing, and do as a result give meaningless "ages." If this is the case, you would still have to be throwing away perhaps as many as a hundred results for every one that you accept in order to achieve 95% concordance.

Radiometric dating is expensive. Geochron Laboratories quotes $750 for each point on a Rb-Sr isochron graph, and $800 per point for Sm-Nd. An isochron graph requires at least three points, and in some cases can consist of a dozen or more. Since researchers frequently use more than one dating method, the cost of dating a single sample can easily exceed $10,000. It's fair to say that it costs as much as a small family car.

This means that if scientists really are cherry-picking data in this way, they must be spending a million dollars or more per published result on what amounts to wholescale scientific fraud. As we've already seen, the number of radiometric results in the literature runs into the hundreds of thousands, with tens of thousands of new results being added every year. The amount of money being squandered must run deep into the tens if not hundreds of billions of dollars worldwide.

Where, then, are the accountants and auditors complaining about this colossal waste of money? Where are the scientists working in other fields, competing with it for funding, creating a stink because they have lost out on research grants because of it? Where are the documents blowing the gaff on it on Wikileaks? And where are the US Senators — some of whom are YECs themselves — calling for the obvious fix to the problem of requiring all radiometric studies to be pre-registered?

Ultimately, the claim that "long age geologists" don't accept results unless they match their preconceived notions is nothing more than a conspiracy theory — and a bad one at that. It may sound plausible when you first hear it, but it only takes some simple arithmetic to see it descend into absurdity. It simply doesn't make sense.