Radiometric Dating is Accurate

Per the definition of "accurate," Con must demonstrate that it is not true that 95% of the dates derived by radiometric dating are within 10% of the true date. Con has only provided evidence that argon dating has some undefined error in some cases, and that a few cases of carbon dating are in error. He offers some unrefereed papers by avowed creation scientists that there are broader problems, but even in those claims, there is nothing that questions the overall statistical accuracy. The arguments are akin to claiming that a wristwatch cannot be used to measure time, because sometimes the battery fails or the display is misread. Errors do happen, but they are well within the claimed error bounds and they are limited by cross-checking. With a wristwatch you check with a different clock, with radiometric dating the checks are with different dating methods and different isotope pairs. Con claims that we cannot know with certainty what the composition of an original sample was. Absolute certainty is not required. Assumptions are made based upon observations. The reliability of the assumptions is ultimately tested by crosschecking to independent dating methods. Radiometric dating is known to be accurate not because it is assumed to accurate, but rather by cross-checking and proving it is accurate. Con is correct that rock samples selected for argon dating cannot have been exposed to air. That is true not only for recent volcanic flows, but with old rocks have fissures allowing air intrusions. One technique is to rely on feldspars formed only at very high temperatures. . http://geology.about.com... The error due to air exposure always makes the sample appear younger than it really is. Different grains of rock from the same location may have different exposures to the air due to the pattern of fissures, so a cross-check is to test several samples to ensure a reliable result. [my ref 1 in R1] There will be consistency among the old dates if the method is applicable. In the opening round, I made the caveat that the methods are only accurate when properly applied. There are also a dozen isotope pairs that cross-check argon dating. The reliability of the dating is further enhanced by cross-checking in the same sample. Con cites A. A. Snelling as to the general unreliability of argon dating. The article cited is in a religious journal, not in a peer-reviewed scientific journal. Snelling is a legitimate scientist who also publishes in peer-reviewed journals. However, he writes in the scientific literature he accepts the accuracy of the standard scientific dating methods. When he writes for his religious audience he denies them. . http://www.noanswersingenesis.org.au... If he had data that would withstand scientific scrutiny, he would publish it in scientific journals. Clearly he does not. Con points out the problem with carbon dating of coal and diamonds. The problem is well known. Coal contains radioactive thorium, and the thorium creates C14 in situ. . http://www.talkorigins.org... As a known limitation, it is not particularly troublesome. It is comparable to knowing that a wristwatch won't work properly in high magnetic fields; once one is aware of that, it is readily avoided. Con claims that there is some general problem with the accuracy of carbon dating for dates after 400 BC. Con quotes Whitelaw, a creationist published by a religious press, not by a peer-reviewed scientific journal. Whitelaw supposes that there was no C14 in the atmosphere more than 5000 years ago, so when he scales all the dates according to his theory they are all within 50,000 years. . http://www.talkorigins.org... Aside from the theory having no scientific foundation, it is contradicted by all the dating methods that cross-reference carbon dating. One must suppose that trees grew exponentially slower in the past, and so forth, to produce exactly the same errors as the error he supposes. Con cites Bowman, a scientist who vigorous supports the accuracy of carbon dating. The British Museum lab doing carbon dating made some errors during the period from 1980-1984. Bowman discovered and corrected the errors. There was no general problem with radiocarbon dating. In the book by Bowman cited by Con, Bowman writes of errors less than 50 years as relatively easy to achieve, and less than 20 years possible with great care. . http://books.google.com... That was written in 1990. Throughout, Con has refused to confront the central proof that radiometric dating is accurate. That proof is that the dates arrived by radiometry are verified by dendrochronology (tree rings), varve chronology (sediment layers), ice cores, coral banding, speleotherms (cave formations), fission track dating, and electron spin resonance dating. The dates are also verified by independent measurements from other isotope pairs. In R1 I presented the challenge to him, "Anyone questioning the accuracy of radiometric methods is obliged to explain why the cross-checks to sediments, coral growth, tree rings, and other isotope pairs all have the same errors. Why would an error in radiometric dating correspond to errors in the other methods so that they all track? In fact, they track because radiometric data is accurate. " Con ignored the challenge. Suppose we suspect that Cousin Lenny's watch is in error. How do we verify it? We check it against other clocks. If the other clocks say it is 3 o'clock and Lenny says it is 3:15, we suspect Lenny has a problem. It is theoretically possible that all the other clocks are wrong and have exactly the same error, but it would take a whole lot of explaining as to how that could be the case. A proper case against radiometric dating ought to begin with a comparison to something believed to be more accurate, and a showing that radiometric dating is not within 10% of that more accurate clock in 95% of the cases examined. Con's problem is that all the reasonable scientific comparisons verify that radiometric dating has the accuracy claimed. All Con has done is cite a few limitations on some of the specific methods. It's true that argon dating cannot be used on samples exposed to air. It's true that carbon dating doesn't work on coal that is loaded with radioactive thorium. Scientists are trained to discover such problems and to avoid them. There are analogous problems with applying virtually any measurement technique. We can list pitfalls with using clocks or micrometers or scales or anything else that measures. That is not at issue. The question is what accuracy is achieved despite all the potential problems. The data show that the accuracy is typically 3%, and with modern technology is approaching 1%.