Radiometric Dating is Accurate

Radiometric dating is the method for establishing the age of objects by measuring the levels of radioisotopes in the sample. http://en.wikipedia.org... One example is carbon dating. Carbon 14 is created by cosmic rays in the upper atmosphere. It decays to nitrogen 14 with a half life of 5730 years. C14 is continually being created and decaying, leading to an equilibrium state in the atmosphere. When the carbon dioxide, containing C14 as well as stable C12 and C13, is taken in by plants it is no longer exposed to the intense cosmic ray bombardment in the upper atmosphere, so the carbon 14 isotope decays without being replenished. Measuring the ratio of C14 to C12 and C13 therefore dates the organic matter for periods back to about eight half-lives of the isotope, 45,000 years. After a long enough time the minority isotope is in an amount too small to be measured. There are about two dozen decay pairs used for dating. Uranium 235 decay to lead has a half-life of 713 million years, so it is well suited to dating the universe. other isotope pairs cover intermediate time periods between the spans for carbon 14 and uranium. Some radiometric dating methods depend upon knowing the initial amount of the isotope subject to decay. For example, the C14 concentration in the atmosphere depends upon cosmic ray intensity. To take this into account, a calibration curve is developed using other dating methods to establish the C14 levels over time. Other methods do not require knowing the initial quantities. For example, potassium decays into two different isotopes of argon having different half-lives. Argon/argon dating works using only the ratio of the concentration of the argon isotopes. It does not use the original amount of potassium. For the purposes of this debate, "accurate" means that 95% of the dating errors are within 10% of the measured date, within the time span for which the isotope pair is utilized. Since carbon dating depends upon variable cosmic ray intensity, a calibration curve is assumed to be applied to account for that. The actual accuracy of radiometric dating is about 2%, but there is no point in splitting hairs for this debate as to whether it is 2% or 3%. An error of 90% would, for example, still disprove Young Earth Creationism. There are three reasons why radiometric data is known to be accurate: 1. It depends upon radioactive decay, which is known to be extremely stable, not influenced my chemical processes, and which can be measured quite accurately. Thus the physical principle of the method is well established. 2. The dates obtained by radiometric dating are verified by independent methods, including dendrochronology (tree rings), varve chronology (sediment layers), ice cores, coral banding, speleotherms (cave formations), fission track dating, and electron spin resonance dating. The multiple checks verify that the rate of isotope decay does not change over time, and it verifies the accuracies of the methods. For dating back to about 35,000 years, sediment layers are precise. http://en.wikipedia.org... Sediments include different types of pollen depending upon the season. Consequently, individual years can be identified by season, so there is no possibility of layers being confused. Sediment columns giving an unbroken history for more than 25,000 years have been identified in about 30 locations around the world. Coral growth patterns are also seasonal and provide a long independent date history. The coral record verifies that radiometric methods are accurate. The data is presented in [1] below. 3. The dates obtained by different radiometric isotope pairs cross-check each other. For the purposes of assessing accuracy, each of the methods is assumed to be applied in accordance with the established methods and technology. By analogy, a stop watch will not keep accurate time if it is not wound, if it is not in good repair, or if the operator forgets to press the button. Methods are precise insofar as they are properly used. A good explanation of all of the dating methods used for samples up to about 200,000 years old, together with their accuracies and references to the scientific literature is contained in [1] Walker, Mike, "Quaternary Dating Methods," John Wiley & Sons, 2005 http://www.amazon.com... 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. An expert scientist summarizes: "The first radiometric dates, generated about 1920, showed that the Earth was hundreds of millions, or billions, of years old. Since then, geologists have made many tens of thousands of radiometric age determinations, and they have refined the earlier estimates. A key point is that it is no longer necessary simply to accept one chemical determination of a rock's age. Age estimates can be cross-tested by using different isotope pairs. Results from different techniques, often measured in rival labs, continually confirm each other. Every few years, new geologic time scales are published, providing the latest dates for major time lines. Older dates may change by a few million years up and down, but younger dates are stable. For example, it has been known since the 1960s that the famous Cretaceous-Tertiary boundary, the line marking the end of the dinosaurs, was 65 million years old. Repeated recalibrations and retests, using ever more sophisticated techniques and equipment, cannot shift that date. It is accurate to within a few thousand years. With modern, extremely precise, methods, error bars are often only 1% or so." -Prof. Michael Benton, (Chair in Vertebrate Paleontology at the University of Bristol, UK, author of 30 books on dinosaurs and paleobiology.) http://www.actionbioscience.org... The resolution is affirmed.