Pathlights' criticisms of C14 dating

The current rate of change of the magnetic field does not necessarily have anything to do with its rate of change in the past. In fact, paleomagnetic data show that the magnetic field is cyclic, has reversed many times in the past, and therefore its rate of change is constantly changing; sometimes it's increasing and sometimes it's decreasing. See Claim CD701 and Is the Earth's Magnetic Field Young?.However, none of this has any relevance to radiocarbon dating! That's because radiocarbon dating does not use present conditions as a reference!Radiocarbon dates are reported in two kinds of years. One is "radiocarbon years", which are based on assuming constant radiocarbon production and other assumprions, but everyone involved understands that radiocarbon years are not calendar years; a sample with a "radiocarbon year" age of 10,000 radiocarbon years is not 10,000 calendar years old.The other kind of years are calendar years, based on calibrating the radiocarbon method against other independent methods. The most commonly used calibration curve is based on tree rings (dendochronology). For example, if we have a sample of wood that dates to 10,000 radiocarbon years old and we know from tree ring measurements that the sample is 11,438 calendar years old, we have established one calibration point. Do this many times and we can draw a calibration curve through the calibration points, and use that curve to translate radiocarbon years to calendar years for any sample (within the range of the calibration curve).The nice thing about calibration curves is that it just doesn't matter how radiocarbon production varied in theh past; that's automatically compensated for.See Radiocarbon calibration. A widely used calibration curve is shown at INTCAL 1998: Tree-Ring Section and a more recent one, including data from other sources and covering a wider range, is at CALPAL 2004 January: there's even an online radiocarbon-to-calendar-year converter (that uses the latter curve) at CalPal Online.[This message has been edited by JonF, 04-26-2004]

Yes. And the calibration curve cancels out that effect, so it disappears and we don't have to worry about it. It just isn't there any more. No, the calibration curve corrects them. Some brainy scientists say the radiocarbon method works and some disaffected crackpots say it doesn't. Sorry, but that's the way it is.

It's a renaissance of the first radioisotope dating method (Rutherford, 1905). (U-Th)/He dating, crudely speaking, dates a rock back to when it reached its closure temperature (75C for apatatite, the most commonly dated mineral). Diffusion is complicated, and what I just said isn't quite true, but it's close enough for jazz. Sylas probably understands closure temperature much better than I do.See (U-Th)/He Basics and (U-Th)/He Chronometry.{edited to add}That's probably not what Zachariah was referring to, he's probably referring to the RATE stuff, but what the heck. Helium is acutally used for dating.[This message has been edited by JonF, 04-26-2004]

Nope. Exactly the opposite.Uranium and thorium are radioactive elements. When they decay, they produce (among other things) helium. Thus, over time, any rock that contains uranium or thorium has helium added to it.When a rock is hot enough the helium escapes. As the rock cools, the rate of helium escape slows down. When the rock gets cool enough the helium doesn't escape any more. It builds up. The more helium the older the rock.The most recent creationist criticism of dating that involves helium is the RATE work, based on some of Gentry's earlier work. Basically, they claim that the helium should have all escaped from rocks in hot areas over billions of years, there's too much helium in these rocks for an old Earth, and this means that the decay happened but it happened over a shorter period of time (accelerated radioactive decay). See Helium diffusion in zircons for a summary of Gentry's work, Helium in zircon - ready for AIG's "do not use" list?, and (from this very group) New helium retention work suggests young earth and accelerated decay.