Mass spectrometers are expensive and rare machines. Only a handful of them are available around the world. So geologists do not do the radiometric dating themselves. When a team needs a date on an important layer at a site, they send their samples to a laboratory, and they await the values. Usually, a single layer is radiometrically dated, and the other layers are given dates in reference to it--higher layers are assigned a younger value, and lower layers are assigned an older value. To eliminate much of the guess work, index fossils are used--a species in a known time period can be used to narrow the exact date of a layer. This is not circular reasoning, since it all begins with radiometric dating. If the mass spectrometer returns a value for a sample from the trilobite layer that actually matches the theoretical age of the dinosaurs, then there is a big problem.
In 1993, a survey was done to collect the age values of samples from various layers thought to represent the K-T boundary. The K-T boundary is a thin geological layer found all over the world that marks the border between the Cretacious Period and the Tertiary Period, or the age of the dinosaurs and the subsequent rise of birds and mammals. It is typified by high concentrations of iridium, shocked quartz, and tektites--clues that the mass extinction was caused by a large asteroid impact. The survey collected those values, and it was reported by G. Brent Dalrymple in his article, "Radiometric Dating Does Work!", of the anti-creationist NCSE website (I do not have immediate access to the original article: Dalrymple et al; Argon/Argon9 age spectra and total-fusion ages of tektites from Cretaceous-Tertiary boundary sedimentary rocks in the Beloc Formation, Haiti). He produced a table containing those ages (and standard deviations) seen here:
A mixture of different dating methods, samples and sites were apparently used--four different decay pairs (Argon-40:Argon-39, Rubidium:Strontium, Uranium:Lead, and Potassium:Argon), three different materials (tektites, biotite/sanidine, zircon/sanidine), from five different sites (Haiti, Mexico, Montana, and two sites in Canada).
I input the values into Excel and calculated the mean and standard deviation of the 25-count array (neglecting the initial standard deviations). I found a mean of 64.7 Ma (million years ago) with a standard deviation of 0.5 Ma. What does this say? It means that a randomly-chosen sample has a 68.3% chance of falling within the range of 64.2 Ma and 65.2 Ma. Not bad. Just for fun, I found that 2 of the 25 initial values were outliers (greater than 2*standard deviation away from the mean). Not bad. 2 outliers were also found when I took 25 readings on a level rod with a leveling instrument in a land surveying lab last quarter.
The mutual corroboration of this set of values is strong evidence for their legitimacy. The corroborations are a counterstrike against the various criticisms that are blithely thrown against it from creationists--that it is selectively reported, that it makes mistakes, that it is inaccurate, and so on. What really seals the deal is that the strength of the evidence is unintentionally confirmed by the Institute of Creation Research, the Creation Research Society and Answers in Genesis. They proposed the following (Carl Wieland, AiG):
Because of the testimony of God's Word, billions of years of radioactivity could not have occurred, so there must have been a speeded-up decay sometime in the past. Never mind that there is no cogent reason why this would have occurred, not in science, not in the Bible, not in theology, not in philosophy--but they have data that needs explaining, and as always they have a miracle-mechanism that can do just that. It may be hard to understand how twisted this seems from my perspective. Thinking about the bare substance of the claim, it seems almost as though the leading young-Earth creationists are fulfilling the dire predictions of their enemies, that their dogmas and methods of argument undermine all sound philosophy of knowledge-building science. To illustrate, the most irritating and offensive caricature of creationism (and seemingly the most politically powerful) is the Flying Spaghetti Monster. The thing that set off all the Internet buffoonery, Bobby Henderson's letter to the Kansas school board, contained this satirical jab:
Since, from the eyewitness testimony of GodÃ¢â‚¬â„¢s Word, the billions of years that such vast amounts of radioactive processes would normally suggest had not taken place, it was clear that the assumption of a constant slow decay process was wrong. There must have been speeded-up decay, perhaps in a huge burst associated with Creation Week and/or a separate burst at the time of the Flood.
There is now powerful independent confirmatory evidence that at least one episode of drastically accelerated decay has indeed been the case, building on the work of Dr Robert Gentry on helium retention in zircons.
At the time I read this, I thought it was very over the top. Creationists don't really believe that God changes the results of scientific measurements, do they? But, in light of the proposition upheld by a consortium of creationists, that God for a very unknown reason at an unknown time caused radioactive decay rates to speed up, how radical is this caricature really? I want to give creationists the benefit of the doubt. I want to believe that they are not their enemy's caricature, that they can recognize inane nonsense when it is handed to them by their leadership. But now how can I continue to sustain that belief?
We tend to be very secretive, as many people claim our beliefs are not substantiated by observable evidence. What these people donÃ¢â‚¬â„¢t understand is that He built the world to make us think the earth is older than it really is. For example, a scientist may perform a carbon-dating process on an artifact. He finds that approximately 75% of the Carbon-14 has decayed by electron emission to Nitrogen-14, and infers that this artifact is approximately 10,000 years old, as the half-life of Carbon-14 appears to be 5,730 years. But what our scientist does not realize is that every time he makes a measurement, the Flying Spaghetti Monster is there changing the results with His Noodly Appendage. We have numerous texts that describe in detail how this can be possible and the reasons why He does this. He is of course invisible and can pass through normal matter with ease.