adele-gQuote:1. How can you claim that carbon-14 dating is useful when "compared with many other radiometric elements, carbon 14 decays quickly. It is useless for dating anything older than about 50,000 years."?
You dont understand its usefulness in context of environmnetal sampling. We use C12,13,and14 in RATIOS that show us whether samples are biogenic , carbonate, contaminated etc. Anyway, I made no such claim about C14. I just pointed out that you made the ORNL story "UP"
Quote:2. How can you determine how much carbon-14 is left in matter when you do not know how much was present in the atmosphere to start with, or how long it has been increasing and decreasing.
Dont need to know anything of the sort. The math of radionuclide decay is simple and robust its an exponential decay
series. All we need
to know is an accurate amount of isotope is present now.
Quote:3. Can you be certain, due to "the effect of variations in cosmic radiation intensity (caused by altitude, depth below the earth's surface, and astronomical events)", of the level of carbon-14 expected to be found in samples?
No , of course not, but once a sample is taken from inside the structure or wood beam , we make sure that we have a good enough GCMS ratio of the isotopes as a "sacraficial sample" before doing the decay analyses. . Anyway, the error is a percentage of the calculated date, not the amount of isotiope present
Quote:4. How can you determine the effect carbon "from surrounding soil, water, vegetation and animal matter", on the sample you are analysing?
5. Considering the dilution of carbon-14 by the release of carbon dioxide from fossil fuel, how do you accurately factor in this dilution? [/Qoute].
This is always the good lab and field QA program. We know that the ratio of C14 to C12 C13 is fairly constant and we calibrate these ratios (also the variation of C14 to 12 and 13 present some good environmental data. At the U of Arizona there is a calibration amount for C14 from tree rings. This gives us a pretty good calibration curve up to about 12K years ago.. For ages beyond that (AND ONLY UP TO ABOUT 50K YEARS) we use lake sediment "seasonal layers and ice cores for total carbon.
In MAZOR 91 "Applied Isotopic ground water Hydrology" theres a good discussion of isotopic calibration of C14 in recent times when atmospheric testing had artificially increased the C14 incorporated in plant tissue.In this case the ratios were affected, and the calibration against H3 was used.
As far as the rest of your post, you seem to have a desrire to especially fault C14 analyses and have forgotten the other atmospheric isotopes , like Clhlorine and Beryllium
Quote:3."There are gross discrepancies, the chronology is uneven and relative, and the accepted dates are actually the selected dates."
I guess I have no idea where you got this from, could you supply me with the source. I dont wish to debate a method with which I work unless I can be sure youre up to speed on the intricacies. I dont have resources here in my vacation home and , Id like to comply with your request (if its an honest one and not some "Clipped " stuff from AIG), then I may as well call Safarti and argue the "quote mining " with him.
There is always a statistical +/- factor in any analysis. Whether youre aware or not, we normally calibrate our MS instruments against a series of "probable" dose/response amounts. We inject "known' values into the machine at low levels to establish calibration curves and from these we run our unknowns. The careful field and lab QA programs have been established for a number of years ,NOT to guarantee zero inaccuraciesbut to alert us whether inaccuracies have possibly occured.
The rest of your quotes appear to be quote mining again, so Ill not coment unless we share the sources and the contexts. Thats only fair to me and Ill try to do the same with you. Ive given you resources, all youve given is OOC quotes that I know arent yours. So where does that place you?
As a reasonable science minded person wishing to learn something about a lab/field technique, or are you someone with another mission. Ill give you the benefit of the doubt for now. Im not trying to be snotty but I get weary of these "quote exchanges" that get us nowhere except to make individuals feel warm and fuzzy with their beliefs.