tag:blogger.com,1999:blog-2361412992308994774.post4342257566927403267..comments2023-11-19T19:19:12.773-05:00Comments on Dealing with Creationism in Astronomy: Some (Probably Not) Final Words on the Nye-Ham DebateW.T."Tom" Bridgmanhttp://www.blogger.com/profile/10889134728080314165noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-2361412992308994774.post-1674361532478167962014-03-10T13:56:37.284-04:002014-03-10T13:56:37.284-04:00At the time of the debate there wasn't a good ...At the time of the debate there wasn't a good web resource on that "old" wood. Now there is at <a href="http://questioninganswersingenesis.blogspot.com/2014/02/45-thousand-year-old-fossil-wood.html" rel="nofollow">"45 thousand-year-old fossil wood encased in 45 million-year-old basalt": Conflict Revisited</a>.<br /><br />Isochrons are used more in geochemistry than in geochronology nowadays. The most widely used method is U-Pb, in which the initial Pb concentration is known to be essentially zero because of crystal-growth kinetics (as acknowledged by the RATE group at <a href="http://www.answersingenesis.org/articles/aid/v6/n1/accelerated-nuclear-decay" rel="nofollow">Helium Diffusion Rates Support Accelerated Nuclear Decay</a>:<br /><br />"Samples 1 through 3 had helium retentions of 58, 27, and 17%. The fact that these percentages are high confirms that a large amount of nuclear decay did indeed occur in the zircons. Other evidence strongly supports much nuclear decay having occurred in the past.11 We emphasize this point because many creationists have assumed that “old” radioisotopic ages are merely an artifact of analysis, not really indicating the occurrence of large amounts of nuclear decay. But according to the measured amount of lead physically present in the zircons, approximately 1.5 billion years worth—at today’s rates—of nuclear decay occurred. Supporting that, sample 1 still retains 58% of all the alpha particles (the helium) that would have been emitted during this decay of uranium and thorium to lead."<br /><br />In addition, U-Pb can often produce a valid age even if the system has not remained closed.<br /><br />Probably the second most widely used is Ar-Ar, which also often produces a valid date even if the system has not remained closed but also can produce a valid dateif the sample had initial daughter product ("excess argon"). The most impressive display of the latter is BGC's tour-de-force of dating the 79 CE eruption of Vesuvius, an incredibly young event by geological radiodating standards: <a href="http://www.sciencemag.org/content/277/5330/1279.abstract" rel="nofollow">40Ar/39Ar Dating into the Historical Realm: Calibration Against Pliny the Younger</a>.Jon Fleminghttps://www.blogger.com/profile/08191822787220580152noreply@blogger.com