The number at the top is how many half-lives have elapsed.Note the consequence of the law of large numbers: with more atoms, the overall decay is more regular and more predictable.(These include the variety of elements used in ‘standard’ radioisotope dating, mature uranium radiohalos and fission track dating.) It would be hard to imagine that geologic processes alone could explain all these.Rather, there was likely to be an answer that concerned the nuclear decay processes themselves.) is the time required for a quantity to reduce to half its initial value.
When physicist Dr Russell Humphreys was still at Sandia National Laboratories (he now works full-time for ICR), he and Dr John Baumgardner (still with Los Alamos National Laboratory) were both convinced that they knew the direction in which to look for a definitive answer to the puzzle of why radiometric dating consistently gives ages of millions and billions of years.Others had tried to find an answer in geological processes—e.g.the pattern was caused by the way the magma was emplaced or how it crystallized. But Drs Humphreys and Baumgardner realized that in other cases there were many independent lines of evidence that suggested that huge amounts of radioactive decay had indeed taken place.Students should be able to understand the principles and have that as a background so that age determinations by paleontologists and geologists don't seem like black magic. Geologists in the late 18th and early 19th century studied rock layers and the fossils in them to determine relative age.William Smith was one of the most important scientists from this time who helped to develop knowledge of the succession of different fossils by studying their distribution through the sequence of sedimentary rocks in southern England.