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Member (Idle past 5260 days) Posts: 766 From: Newcastle, Australia Joined: |
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Author | Topic: Pathlights' criticisms of C14 dating | |||||||||||||||||||||||||||
NosyNed Member Posts: 8996 From: Canada Joined: |
There are, as noted, anomolies. This work is done to allow careful and accurate use of the dating methods.
That fact that the methods work very well is demonstrated by the correlations between dates derived through other means and the dates measured using C-14 dates. Historic artifacts of know date and the dating of things like tree rings and varves support the C-14 dates. All the careful choosing of anomolies doesn't do anything to through the method into doubt when it is supported so well. You experiment is not well designed. I'll leave it to you to figure out why. Or we can discuss it in detail later.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
from Wiens (Radiometric Dating)
15. Low abundances of helium in zircon grains show that these minerals are much younger than radiometric dating suggests. Zircon grains are important for uranium-thorium-lead dating because they contain abundant uranium and thorium parent isotopes. Helium is also produced from the decay of uranium and thorium. However, as a gas of very small atomic size, helium tends to escape rather easily. Researchers have studied the rates of diffusion of helium from zircons, with the prediction from one study by a young-Earth creationist suggesting that it should be quantitatively retained despite its atomic size. The assumptions of the temperature conditions of the rock over time are most likely unrealistic in this case. I find it interesting that this appears to be the opposite result? One set of zircons with too little helium and another with too much? You might want to contact Wiens and see what he has to say. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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JonF Member (Idle past 168 days) Posts: 6174 Joined: |
According to the technical monograph "Origin and Destiny of the Earth's Magnetic Field," the magnetic field is decaying as a first order exponential with half life of 1400 years, a number much less than the 5700 year half life of C14. The consequence of the decay is that there is corresponding exponential increase of the generation rate of C14. Using present conditions as a reference will result in an increase in the apparent age of older samples." 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]
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Zachariah Inactive Member |
correct that is how they can determine the age the older the rock the less the helium. Helium escapes through time and they can then use that to help determine the age, make sense? They dug a hole and the deeper they go the older the rock and the less the Helium. It just verifies there hypothesis.
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Zachariah Inactive Member |
Interesting. The thing I got from it was that the magnetic field does effect the Carbon readings through time. And if it does change in cycles throughout time then all the dates you refer to would be incorrect. So some brainy scientist says no others say yes and the fight keeps going. There will never be an end. Actually there will be one in the future, but I'm good to go.
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Coragyps Member (Idle past 735 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
It's well known that 14C has varied over time. That's precisely why the 14C clock has been calibrated against layers in ice, tree rings, layers in lake bottoms, and layers in the ocean floor off Venezuela. Guess what: the dates are probably "incorrect" by as much a 3% back around 40,000 years ago. But they're getting more precise every year, as measurement methods improve.
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NosyNed Member Posts: 8996 From: Canada Joined: |
This helium content? Is this a new dating method? It's something I haven't seen any details of. Perhaps you can supply more details.
You have a bunch of "they"s in there. Who is "they"?
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
read it again, read the source given. you are taking it out of context.
{{added by edit}}for more on calibrations and correlations of dating methods see EvC Forum: Age Correlations and an Old Earth Age Correlations and an Old Earth Enjoy. [This message has been edited by RAZD, 04-26-2004] we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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JonF Member (Idle past 168 days) Posts: 6174 Joined: |
Interesting. The thing I got from it was that the magnetic field does effect the Carbon readings through time. 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.
And if it does change in cycles throughout time then all the dates you refer to would be incorrect No, the calibration curve corrects them.
So some brainy scientist says no others say yes and the fight keeps going Some brainy scientists say the radiocarbon method works and some disaffected crackpots say it doesn't. Sorry, but that's the way it is.
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NosyNed Member Posts: 8996 From: Canada Joined: |
...time then all the dates you refer to would be incorrect. So some brainy scientist says no others say yes and the fight keeps going. There will never be an end. So you're saying that there are a few individuals (with a stated axe to grind and no particular expertise in the area) who give a few examples of what they think are problems. These same individuals ignore a huge amount of other data. From this you conclude that there are real problems? This you conclude even though 1,000's of other individuals who do have expertise in the area disagree. You stick with this even though other data showing the correctness of the method is ignored by your few. You continue to think your few might have something even though there are many other methods which produce results showing your few wrong. This is a logical process in your mind? [This message has been edited by NosyNed, 04-26-2004]
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JonF Member (Idle past 168 days) Posts: 6174 Joined: |
This helium content? Is this a new dating method? 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]
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JonF Member (Idle past 168 days) Posts: 6174 Joined: |
correct that is how they can determine the age the older the rock the less the helium. Helium escapes through time and they can then use that to help determine the age, make sense? 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.
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Zachariah Inactive Member |
Thank you for the correction. I really scanned over the article quickly and thought I had a grasp of what it was saying. Maybe I'm lisdexic.
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