I dated a Carbon-14 once. I took her to this really nice restaurant and everything, and all through the meal all she did was drone on and on about her problems with her mother. Bleah. I’d originally planned to take her out dancing afterward, but I made up an excuse to cut it short and took her home.
Stick to dating good old-fashioned radioactive Argon instead. They tend to be much nicer.
Carbon-14 has a half life of 5730±40 years. It’s useful for dating specimens younger than about 50-60,000 years. Very accurate calibrations of the C-14 dating method for the past 10,000 years have been found by comparing C-14 levels to tree ring data.
Given the proven accuracy of C-14 dating, it is not surprising that the occasional anomalous measurement might be ignored if other factors strongly indicate a specific age. The preponderance of evidence shows the method accurate; chasing down the causes (often measurement or preparation errors) of every anomalous result is usually unproductive. The absence of a C-14 measurement in a scientific paper where it would normally apply is conspicuous in and of itself. Were the actual measurement relevant, the competitive nature of scientists would usually ensure that the lack would be investigated.
Radiocarbon Web Info
I seem to remember that I was chastised for engaging in argumentum ad hominem in the thread this poster alludes to. Well, I can do better than that. If anyone doubts my contention, why don’t those of you more predisposed to this type of research, take a look at the findings of the 1972 Uppsala convention? And while you’re at it, read Allan Sandage. 
dougie_monty-you never actually READ anything before you post do you? jonf already said (just three post back mind you! no using the “i have to spend 12 bucks an hour to get online and can’t read everything” line) that he couldn’t find much on that conference (and the brief mention he could find said the conference was in '68)…it’s YOUR reference, why dont YOU find it and share it with the class?
correction: 1969
Well, looks like gillygirl took my response. But since I know from experience that it’s difficult to get things through to d_m, I’ll repeat:
You made the claim. You back it up.
dougie_monty:
As has already been pointed out, there appear to be no references to your alleged conference in Uppsala on the web. If such a conference ever took place and produced the result you claim, I’d definitely expect to find a reference in the “creation science” literature; they’re very good at finding anything that could conceivably be interpreted (or even mis-interpreted) as questioning the validity of C14 dating.
In addition, I’ve done a keyword search of the MIT libraries and they have no holdings that appear to be related. They do have lots of holdings that include Uppsala …
You claim there was such a conference and you claim a particular result emerged. There’s very convincing evidence that both those statements are wrong. Got any reason (such as a reference) why anyone should believe that conference ever took place?
I suppose you mean Dr. Allan Rex Sandage, the astronomer, winner of the 1975 Bruce medal, author of A Scientist Reflects on Religious Belief and author of several technical books on astronomy? The one who is in a field having nothing to do with carbon dating? The one who, as far as I can tell, has never written anything remotely related to carbon dating?
What do you think Allan Sandage has to do with this discussion?
gillygirl: A minor amplification. While I did find a reference to a conference in Uppsala, it has yet to be established whether that conference ever took place; and, if it indeed took place, it has yet to be established whether that’s the conference to which dougie)monty referred. The quote I posted does not say what dougie)monty claimed was said at his alleged conference.
I’ll go with the, “it’s a pretty good approximation” stance.
Half-life or radioactive decay rate is not an intrinsic property of an element per se. It is, rather, an average; or, more specifically, an integration of the mean square of the probability that the event will occur. If you have one atom of C-14 it may decay now, tomorrow, or never. It has a probability of decaying at a certain time, but not a certainty. However, the more atoms of that material that you have, the closer the average of the decay rates of the individual atoms gets to the theoretical limit. (in this case ~5700 yrs.)
Given that, an argument might be made that the smaller the starting material, the larger the possibility for error is. That on its face is true. However, given that 14 grams of C-14 contain 6.02 X 10^23 atoms; you would have to go well beyond the detectible amount in order for that error to be of any significance whatsoever.
The problem with C-14 dating is (as stated before) with the variances of atmospheric C-14 over time. Corrections have been made through the use of dendrochronology and analyzation of ice plugs in glaciers, that have made C-14 dating relatively accuate back to a few thousand years. So when Argon-West National Labs concluded that the shroud of Turin is only about 1 thousand years old, I tend to believe them.
I’ll have to wait until my next access to the Internet, but when I do (I have jury duty for the upcoming two weeks) I will furnish on this thread not only the requested quotation from Allan Sandage–in which he takes up the matter of a “zero point”–but some other comments on the matter of Carbon-14 dating. I have also found out, interestingly enough, that the proponents of radicarbon dating on one hand and the biologists who use tree rings for dating (as with the famous California bristlecone pine), on the other hand, have used each other’s data and hypotheses to support their own. 
dougie,just so you dont forget when you give us references to your other stuff after you get back…WHAT ABOUT THE CONVENTION?? <-sorry to yell, but i find sometimes its the only thing that works when youre dealing with someone who ignores your questions (im a 911/police dispatcher, i know alllll about people like that)
I wonder why you put “Allan” in italics; you used “Allan” in your original message, I used “Allan” in my reply. “Allen” appears nowhere in this thread.
So, like I said, Allan Sandage who apparently has never had anything to say about C14 dating and is a somewhat well-kown scientist who may know nothing about C14 dating.
It’s been just over two weeks since dougie_monty promised references in two weeks …
I’ve taken a couple of Archaeology classes so I hope I can shed some light on this subject. The reason that you can’t just hack down some tree that you think is the same age and try and take a C-14 date is because the item must be dead. That is that the organisam stops taking in C-14 when it dies and you can only tell when it died, not for how long it lived so if you cut down a tree today it wouldn’t help to take the C-14 because C-14 will not tell you the age.
There also has been some variation in the amount of Carbon in the atmosphire and it does cause some variation. The last that I heard C-14 has a variation of ± 40 or 50 years. The other problem with C-14 is that the organism may have been dead for a long time, like a tree, and then used to make shelter the sheler could have been made hundreds of years later so C-14 can only tell you when it died not when it was used. I don’t have any references for this as I stopped buying books when I didn’t read them any more and MY interst in Archaeology is mainly in Megaliths so I don’t read much about C-14. I do know that any basic Arch book will have all of that in it and they can be easily found at the book stores.
OK I broke and got a link
http://www.radiocarbon.org/Info/index.html
there’s a “basics” section that I really didn’t read but it should all be there, plus loads of links.
23 days ago, Danielinthewolvesden wrote:
Sorry to pick at such an old, stale nit, but:
The gap in time between when the Earth cooled and settled to a stable enough state to support life, and the dates of the oldest known microbial fossils, is only around 300 million years.
It’s not the whole tree that is dated, but the individual rings. The cambium (sp?) layer, just beneath the bark, is the living portion of the tree. As the tree grows, last year’s cambium layer dies off to form a new ring, and a new layer is formed. The inner rings are, for all intents and purposes, dead – they can be dated, and the innermost rings will give a close approximation of the tree’s age.
Since the rings can also be counted, dendrochronology can be compared with C14 ages to determine the accuracy of the latter.
Also, since Uranium can substitute for calcium in limestone, U-Th chronology (which, as stated earlier, is not dependent upon cosmogenic production) can be compared to C14 chronology in coral reefs.
Production rates of cosmogenic radionuclides vary due to a variety of factors, including the flux of primary cosmic ray particles and secular variations in the Earth’s magnetic field.
These variations are well-documented by comparison with independent chronometers (such as tree rings and U-Th), and there are published correction factors for C14 measurements. This is a science, not guesswork.
The trick used to be isolating enough carbon to do decay counting, but with the advent of accelerator mass spectrometry carbon samples as small as a milligram can be measured in a few minutes.
jrepka wrote:
Coral reefs? I thought C-14 dating wasn’t any good for looking at the remains of critters that live under water. Or are we talking about the part of the coral reef that pokes up above the water line?
All reefs form at or near the surface, but the primary assumption in C14 dating is that the reservoir is well-mixed, especially at the time scales we’re dealing with. The only limitation I can think of that might create a problem is recrystallization of the calcite. This is dealt with by looking at the crystalline lattice.
Many organisms that form calcite tests will create a unique form of calcite known as aragonite. It is chemically identical to ordinary calcite, but has a higher symmetry (six-fold, I believe, as compared with three-fold). Aragonite, being more ordered, can only be formed by living organisms. As limestone ages and recrystallizes, the aragonite converts to ordinary calcite.
If you want to do C14 dating of shells you want to use organisms that form aragonite tests, so you can make sure that there hasn’t been recrystallization.
I’ve never dated anyone under 14, carbon or not!
I am pleased to say that my jury service is over. (It had been extended, rather, postponed–I had a job interview I couldn’t miss. )
I confess that I have not been able to locate documentation to bolster my claim about C-14 dating being questioned in a conference in Uppsala in 1972. In fact, unless I eventually do find such documentation I will have to retract the claim.
That said, here is some commentary about Carbon-14, and Potassium-Argon-40, dating:
“Any increase in radiation levels…most certainly would ruin some of our carefully developed methods of dating things from the past…If the level of carbon-14 was less in the past, due to a greater magnetic shielding from cosmic rays, then our estimate of the time that has elapsed since the life of the organism will be too long.”–Science Digest, December 1960, p. 19.
“Through radioactive dating methods, the age of the earth has been approximated at 4,500 million years. A new and higher figure–6,500 million years–has been given by E. K. Gerling of the Laboratory of Pre-Cambrian Geology of the U.S.S.R. Academy of Sciences. Pre-Cambrian rocks that had been formed at great depths below the surface of the earth were dated by Prof. Gerling and his associates using the potassium-40 argon-40 method…the Soviet’s new age for the earth may be the result of some overlooked factor in the potassium-argon dating technique.”–Science Digest, December 1962, p. 35.
“The drawback with the [radioactive-decay] method is the lack of general distribution of radioactive minerals and the fract that these radioactive minerals have suffered such a large amount of radiation damage that they frequently show ages that are not concordant.”–How Old Is the Earth? (1959), p. 105.
“For nearly 50 years [from 1917 to 1967], the dating of the Vinca culture [in Roumania] has been an open controversy among anthropologists. A radiocarbon test of burnt wood splinters from the Vinca area in 1953-54 indicated that they dated from about 4100 B.C. But this date contradicted the evidence of rock strata, which suggested that the culture dated from about 2900 B.C.”–New York Times,, March 26, 1967.
"Although it was hailed as the answer to the prehistorian’s prayer when it was first announced, there has been increasing disillusion with the method because of the chronological uncertainties (in some cases, absurdities) that would follow a strict adherence to published C-14 dates…
“What bids to become a classic example of ‘C-14 irresponsibility’ is the 6000-year spread of 11 determinations for Jarmo, a prehistoric village in northeastern Iraq, which, on the basis of archeological evidence, was not occupied for more than 500 consecutive years.”–Science, December 11, 1959, p. 1630.
And here is the comment about dating methods by Allan R. Sandage:
“We know the amounts of these elements in the world today. We can read the time if we can find out how these elements formed, for we can then estimate how much of each was made.”–Science Year of 1968, p. 64. According to Sandage, scientists cannot determine this key point “because no astrophysicist was present at their creation.”
Additionally,
“Unfortunately, one may only guess these concentrations [of radiactive materials], and the age results thus obtained can be no better than this guess.”–Melvin A. Cook, Prehistory and Earth Models, p. 24.
For my own part, I would be hard put to trust a clock if I were not sure that it had been set at the right time and I knew its gears were damaged.