Talk:Radiocarbon dating/Archive 4

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== Carbon Exchange Reservoir in the Real-World ==

The following secion has been removed here for discussion as there have been serious objections and problems - rather than engage in a revert war let's discuss here: Vsmith 02:12, 24 January 2007 (UTC)

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Libby's original exchange reservoir hypothesis assumes that the exchange reservoir is constant all over the world. The calibration method also assumes that variation in ¹⁴C level is global, such that a small number of samples from a specific year are sufficient for calibration. This may not be true. The following variances are seen in the real world:

• Erosion and immersion of carbonate rocks (which are assumed to be too old to contain ¹⁴C) causes an increase in ¹²C and ¹³C in the exchange reservoir, which depends on local weather conditions and can vary the exchange ratio.
• Volcanic eruptions eject large amount of carbonate rocks (which are presumably too old to contain ¹⁴C) into the air causing an increase in ¹²C and ¹³C in the exchange reservoir that is local to the volcano and can vary the exchange ratio locally.
• ¹⁴C is known to behave chemically different than ¹²C and ¹³C (due to different atomic mass), which means during decomposition of organic material there is no guarantee that the carbon ratio of the material will stay as it did at material death.
• The earth is not affected evenly by cosmic radiation, the magnitude of the radiation depends on land altitude and earth's magnetic field strength at any given location, causing local variation in ¹⁴C production.
• Oceanic water mixing rate is assumed constant and instantaneous, but it takes 1500 years for all water in the pacific ocean to mix.
• Wood has been found to accumulate ¹⁴C in its center due to the difference in chemical behavior of ¹⁴C compared to ¹²C and ¹³C.

These effects were first confirmed when samples of wood from around the world, which all had the same age (based on tree ring analysis), showed variance of up to 8.5% from the expected per minute decay frequency, assuming they had the same ¹⁴C ratios. This meant the dating of the samples varied by as much as 700 years. The error of dating an object of unknown age will be the accumulation of the all the variances (each possibility as high as 8.5%) in the decay rate of every calibration sample. This means as more calibration samples are obtained the total error will decrease until it reaches error of local variances in the exchange reservoir, which is currently unknown. For this reason the accuracy of ¹⁴C dating remains in dispute.

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Comments -

The references are mostly from the 1950s and 60s and are not readily available to those of us in the boonies. The dated refs themselves pose a problem - i.e. are they outdated? What is the context of the referenced material? Would I or Jclerman read it differently?

User:Jclerman has extensive experience and background in the field of radioactive dating, but currently may not have access to the old paper refs used to verify the use and interpretation as used in this section.

The poster of the above information seems, from his user page, to have limited expertise in the field. This brings the possibilty of mis-interpretation of the original sources - thus verification is needed.

The comments that the isotopes behave different chemically is quite contrary to what little I know about isotopes. The only difference is that of mass which provides a physical segregation or fractination under varying conditions.

More specifics follow, Vsmith 02:26, 24 January 2007 (UTC)

Specifics, Erosion of carbonate rocks does provide old carbon with no C-14. However this is a continuous global process and the eroded old carbon is thorougly mixed within the reservoir and is a part of that reservoir.

Volcanic eruptions do not erupt or eject large amount of carbonate rocks. Carbon dioxide is a constant part of volcanic emmissions and is thouroughly mixed throughout the atmosphere reservoir. Local effects are but transitory.

C-14 does not behave different chemically. The fractionation effects are physical and well known. If the dead carbon material is not decomposed - if is is preserved there should be little fractionization after death/burial. If it is thoroughly decomposed - of course that means it probably is not useable. The carbon has been gobbled up by the decomposing organisms.

Cosmic radiation may well be variable - but how this would cause local variation in C-14 escapes me. Global variations can and do occur and that's why calibration curves bases on dendrochronology and other methods are used.

Ocean water mixing? No source here - but 1500 years for all water to mix? Don't really see the relevance.

Wood. Again chemical behavior problem. Don't know about the accumulate in the center bit - confusing here and I don't have access to that 1957 issue of Tellus to check for clarification. Nor do I have acces to Libby's 1962 publication to check context, etc.

Vsmith 02:53, 24 January 2007 (UTC)

Hi Vsmith. Regarding the point about the ocean, I presume attention's being drawn to the heterogeneity of the ocean's ¹⁴C inventory. Deep North Atlantic water has a very different content from deep North Pacific water because they lie at opposite ends of the thermohaline circulation. Therefore the supply of ¹⁴C to the deep Pacific (ultimately the atmosphere, where it's generated) takes a long time (in terms of ¹⁴C half-life) to get there. It would be helpful to have a source for the 1500 years though (the thermohaline page suggests: Primeau, F., 2005, Characterizing transport between the surface mixed layer and the ocean interior with a forward and adjoint global ocean transport model, Journal of Physical Oceanography,35, 545-564; but it is a model). --Plumbago 12:31, 25 January 2007 (UTC)

P.S. As an aside, more recent publications, as well as being more accessible, are often more desireable than old publications because the latter are occasionally misused ("cherry-picked"). If I see a contentious point (to me that is) backed up by an old cite, I tend to suspect said contentious point of being bogus. Then again, perhaps I'm just an overly suspicious sort ...

Not so old references (that I have found so far):

• R. E. Taylor Use of Natural Diamonds to Monitor Radiocarbon AMS Instrument Backgrounds at The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005).Abstract- Diamonds (at least the one measured) shows ~50kyr age using AMS
• Bird et. al. Radiocarbon Dating of “Old” Charcoal Using a Wet Oxidation, Stepped-Combustion Procedure, Radiocarbon, 41:2(1999), pp. 127-140. - All coal is (by totally unknown means) contaminated at the 0.2 percent modern carbon level ( 100X the AMS measurability limit of ~ 0.002 pmc).
• Peter G. Brewer Major International Programs in Ocean Sciences: Ocean Chemistry in 50 Years of Ocean Discovery: National Science Foundation 1950-2000 (2000) (pp. 152-162). - "[T]he mean replacement times for the Pacific, Indian, and Atlantic ocean deep waters (more than 1500 meters deep) [are] approximately 510, 250, and 275 years respectively. The deep waters of the entire world ocean are replaced on average every 500 years." - Quoting Stuiver et al. from Abyssal water carbon-14 distribution and the age of the world oceans. Science 219:849-851 (1983)
• Baumgardner et al., The Enigma of the Ubiquity of ¹⁴C in Organic Samples Older Than 100 ka, AGU Fall Meeting Abstracts, 2003[1]

Dan Watts 02:02, 29 January 2007 (UTC)

I originally wrote most of the section to explain the carbon exchange system that carbon dating is based on and point out the possible sources of error as Libby stated, rather the than non NPOV that C14 is prefectly made and transfered as the rest of the article would seem to imply. The sources were from modern papers that I referenced back to these originals to prevent people from going from book to book to book just to find a source. I don't see why you consider them 'wrong' simply because they are old but I can see many people are using the section as an excuse to insert things i didn't write like "This may not be true." amd skew to a POV that carbon dating is wholy inaccurate.

I find it pretty sad that you believe it is 'contested' because you haven't got hold of the sources and don't believe them. Statements like "Cosmic radiation may well be variable - but how this would cause local variation in C-14 escapes me." are not going to help the discussion here. It is explain in the referenced articles how latitude/longtidue will cause variance in cosmic radiation creation depending on geographical location, if you newer source to state otherwise please list it. Unless there is a source showing consitant measurements of cosmic radiation C14 production at different geographical locations I don't see how the 'old' source should be outdated simple for being 50 years to old, Libby also expressed that the dating is based on universal equal cosmic radation geographically, which he states is an assumption of the hypothesis of carbon dating, and that is why a single sample can be used to calibrate that date for the whole earth, rather than having to get samples for every year from every different region. Unfortunently the truth is the studies haven't been done. And as per the sourced article, as libby states, tree ring dating from the same years has been upto 700 years different. Most documentation about carbon dating comes from the era around its creation, even modern documents all link back to it because the fundamental hypothesis is not changed. Eitherway the description of C14 creation/exchange in the article without this section is very poor.--155.144.251.120 03:23, 29 January 2007 (UTC)

For the variation of cosmic radiation over the earth to reasonably be a factor, the mixing time of carbon dioxide in the atmosphere would need to be long (see: [2] and [3] which opine that the time for uniform mixing of the atmosphere is ~ 1 year) and this does not appear to be the case. Longer term variations (such as the sunspot cycle) would affect carbon dating. Dan Watts 18:13, 31 January 2007 (UTC)

According to the conventional view not only is the production of C14 locally variable, it is solely restricted to the polar regions alone. With replenishment being 0.012 %/a mixing would have to be exceedingly slow for that to build up. And as shown in the article an experiment has been made. After the nuclear tests C14 was doubled in the northern hemisphere relative to the southern and the ratio equalized in about five years. What more do you want? Axel Berger 08:26, 1 February 2007 (UTC)

I want some sort of mention of the error rate for a start. Even libby's documents show wood of the same date being aged upto 700 years apart. There are assumptions in the hypothesis which should be stated here, other wise it gives the impression that carbon samples are 100% accurate.--Dacium 02:32, 6 February 2007 (UTC)

NPOV tag

Is there a consensus (I know there will not be unanimity) to remove the NPOV tag on this article? There seems to be no real dispute here, just one or two people trying to push a non-scientific POV. Comments? Raymond Arritt 15:05, 12 February 2007 (UTC)

I do not think that non-scientific POV belongs in this article. I think there is a current POV dispute however regarding whether the fact that some groups dispute the accuracy of carbon dating should be included in this article. I think however that any such inclusion should include its sources, and also should include the basis of any such dispute. --Rebroad 15:56, 12 February 2007 (UTC)

Not sure I follow you here. Is "some groups" shorthand for young-earth creationists? Raymond Arritt 16:07, 12 February 2007 (UTC)

Linkspam?

I'd argue that this link is spam and a violation of WP:EL:

• http://www.thebaptist.org/carbondating.htm

What do others have to say?

Atlant 16:38, 12 February 2007 (UTC)

I would agree with you - keep it out. Vsmith 16:41, 12 February 2007 (UTC)

Proposed merge

• No. Radiocarbon dating is sufficiently "unique" and notable to have its own article. Vsmith 16:41, 12 February 2007 (UTC)
• Don't merge -- It's sufficiently well known and of historical prominence to merit a separate treatment. Raymond Arritt 16:43, 12 February 2007 (UTC)

• Don't merge -- For the reasons stated above. Atlant 16:56, 12 February 2007 (UTC)

• Don't merge - Aside from its notability, this article is far too long for a merge. I'm also a little concerned that this merge request is coming from a (currently disruptive) editor. It feels like an attempt to achieve some goal by any means necessary. --Plumbago 17:11, 12 February 2007 (UTC)
• Don't merge. Jclerman 22:07, 12 February 2007 (UTC)
• Don't Merge. Radio carbon dating is based on C14 which is created by cosmic rays. Radio metric dating is usually using radio isotopes that were only created at the start of the universe. Radio carbon dating is unique in this respect.--Dacium 01:32, 20 February 2007 (UTC)

Tag removed - as there was no support for a merge. Vsmith 03:10, 20 February 2007 (UTC)

Religion redux

From WP:FRINGE: "Theories which have not received critical review from the scientific community should be excluded from articles about mainstream scientific subjects. If the purpose of the article is to explain a scientific subject and there are people who dispute this subject, unless there is a verifiable refutation from the scientific community the theory does not represent a significant minority opinion within science itself. The theory may still be written about and expounded upon in articles devoted to the theory itself or non-scientific contexts." Based on this, unless sources can be cited showing mainstream scientists critically reviewing the creationist claims, it doesn't belong in the article. If sources can't be added (from scientific publications, not religious ones), that section needs to be deleted from this article. It certainly could go in an article about creationism or another religious article. --Milo H Minderbinder 17:09, 12 February 2007 (UTC)

Agreed. Echoing my earlier point above, the current "Controversy" section in the article should be removed simply because creationists are not specifically objecting to carbon dating, but instead are put-out by any methodology that fails to agree with their particular interpretation of religious texts (and let's not forget that there are dozens of mutually-incompatible, theologically-grounded chronologies of the Earth). As such, they bring nothing interesting to the table on carbon dating, bar disingenuously harping on about known issues the technique has; which are covered more authoritatively (and objectively) by the science content of the article anyway. Many scientific articles contain (or imply) information which is liable to offend such religious sensibilities, do we really need to add a "Controversy" section to all of them? --Plumbago 13:09, 14 February 2007 (UTC)

Removed it. --Milo H Minderbinder 14:05, 14 February 2007 (UTC)

Is anyone opposed to removing this now from Wikipedia:Requests_for_comment/Maths,_science,_and_technology?--Atemperman 04:53, 2 March 2007 (UTC)

Go for it. Discussion here stopped a long time ago, with the consensus that the creationist viewpoint be removed. --Plumbago 08:59, 2 March 2007 (UTC)

Plumbago, I am concerned about your attitude which seems to suggest a position of neutrality towards worldviews, which is philosophically impossible. Your worldview is atheistic? Then your presuppositions are such that they *begin* with a disbelief in God - and that fact will affect your conclusions as well. Perhaps when you assert that Creationists are "disingenuously harping on about known issues the technique has", those very issues are at the core of radio-carbon datings' failure to be truly scientific. I don't mean to be rude, but a the creationist view at "http://christiananswers.net/q-aig/aig-c007.html" seems to be particularly scientific, casting adequate doubt on the issue. Please don't assume that atheistic presuppositions are automatically aligned with objectivity. I would honestly like a fair appraisal of the Christian Answers websites' contribution to Radio-Carbon dating. Anyone? —The preceding unsigned comment was added by 210.10.134.203 (talk • contribs).

Hi 210.10.134.203. Sorry if I sound gruff in my comments above, but I'm afraid that comes from having to answer creationists on points like this time and time again. There are simply no good grounds for rejecting radiocarbon, or other radioisotopes, for dating purposes. Yes, these methods have caveats and methodological limitations, but these are well-understood. I could spend hours dissecting the claims made at the website you mention above, but I doubt I could do as good a job as the editors at Talk.Origins. They have a number of resources dealing with the "criticisms" levelled by creationists. Finally, I agree that one shouldn't assume that one's presuppositions (whatever mine actually are) are automatically aligned with objectivity, but I'd direct you to the closing line from the website you mentioned: "We don't have all the answers, but we do have the sure testimony of the Word of God to the true history of the world". Now that's presupposition for you. Cheers, --Plumbago 13:43, 16 August 2007 (UTC)

Unrelated to creationists, I in fact know about a minority opinion disputing accuracy of radiocarbon dating in archeology. For examples see [4], pages 75-77 (yes, I know; but the examples are independent of the author). Some of it is already mentioned in the article in "Carbon exchange reservoir in the real world" section, so I think that the rest could be mentioned too. Nikola 12:19, 26 March 2007 (UTC)

Deja vu. Somebody has already written a lot of nonsense sans the citation to this peculiar Russian mathematician. So, now we know why the two Nauka articles were cited sans volume and page numbers and why copies where neither posted nor sent to us. With so little info we can't afford to browse the thousands of Nauka publications archived in libraries. Most of all the critiques are irrelevant. As irrelevant as citing Ptolomeus to discuss global warming. Consider that calibration of the dating scale overrides all the exchange reservoir "problems" mentiopned. Leave the reservoir problem to the geophysics and geochemistry research that tries to find out where to put the excess of atmospheric CO2. The radiocarbon datings are based on calibrated measurements. And, note that, personally, I can't accept discussions based on material which is "pre Nobel Symposium" because it would be a waste of resources unless intended for a historical review of the genesis of ideas relevant to dating methods. As I said above already: All variations and calibrations were described not in Libby's works (ca 1950) but in the "12th Nobel Symposium" (1970). I suggest you read it. You'll find detailed answers to your questions. The article in the wikipedia is not intended to be a "how to do it tech manual". Regretfully some of us have limited access to physical libraries either by geography or by health reasons. Your contributions will be greatly appreciated but you'll have to do some leg work. Incidentally, much of the critiques of Libby or about Libby's results in the above discussions are irrelevant. I'd rather delete the section on reservoir exchanges since it is irrelevant for calibrated dating. Little has been dated using Libby's techniques. It was Hesel de Vries who established the modern basis of radiocarbon dating, expanded upon in the mentioned Nobel Symposium. See Paul Damon, "online" electronic mail interview, October 29, 1998. Interviewer Theodore Feldman in [5] Jclerman 21:26, 24 March 2007 (UTC) Jclerman 14:49, 26 March 2007 (UTC)

Well I wouldn't call the critiques completely irrelevant. I wouldn't edit the article but perhaps someone more knowledgeable could add something along the following lines:

• A simplified view of radiocarbon dating is that Earth's atmosphere contains certain amount of C14, which living organisms incorporate into themselves, and that by measuring of amount of C14 in their remains we can know when did they live.
• In practice however, this is complicated by the following: 1) amount of C14 in the atmosphere is not constant over time, including gradual global changes and abrupt local changes; 2) amount of C14 in the atmosphere is not constant over entire globe, again including gradual global changes and abrupt local changes; 3) C14 is not incorporated in the organisms in the same way other carbon isotopes are because of different chemical properties; 4) carbon exchange with the atmosphere can occur after death of organisms.
• 1) and 2) can be accounted for by various calibration techniques, though not entire globe is calibrated with the same precision; actually, that is pretty much what the article already says. 3) can be accounted for by analysis of these reactions, but no one does that; the article says that the effects are extremely minor, and to me it seems that there is a scientific minority which doesn't think that the effects are extremely minor, so perhaps it should be mentioned. 4) is not mentioned and I think it should be. Nikola 11:09, 29 March 2007 (UTC)

It's a trivial observation, but your point number 4 applies both to ¹⁴C and other isotopes of carbon (though not necessarily equally; see your point 3). So any loss of ¹⁴C to the atmosphere after death will be accompanied by a proportional (-ish) flux of other carbon isotopes to the atmosphere. As I understand it, ¹⁴C methodologies don't assume that carbon exchange after death doesn't occur, rather that such a flux isn't restricted to ¹⁴C (i.e. if one uses the ratio of radioactive to stable isotopes in a sample to age it, it doesn't matter if X% of the sample has been respired away post-mortem).

On your point 3, studying the shifts in the ratios of stable isotopes io biological/chemical/physical processes is actually a moderately large field (with a wide range of applications, including odd things like paleoclimatology). Again, as I (mis)understand it, these shifts are small but significant for the processes under study. However, as ¹⁴C shifts can be extremely large (a loss of 50% every 6 ky), these smaller shifts caused by isotope discrimination are less significant for radiocarbon dating. Still, a description of this in the article wouldn't hurt. Cheers, --Plumbago 11:44, 29 March 2007 (UTC)

I understand that loss of carbon after death occurs during decomposition, when it is affected by subsequently changing carbon ratios in atmosphere. Nikola 12:20, 29 March 2007 (UTC)

A few points here. Firstly, although decomposition respires carbon from a potential sample, isotopic discrimination during this is not strong (as I understand it). Secondly, for a potential sample to become a sample, it has to not decompose (at least not much); otherwise we'd have no sample to examine. Decomposition, of course, is the reason why almost all potential samples fail to become samples. Thirdly, carbon lost from a sample due to decomposition (¹²C, ¹³C and ¹⁴C) or through radioactive decay (¹⁴C only) is not replaced from the atmosphere. So the atmospheric composition of carbon isotopes is irrelevant on this point. Finally, although the recent (post-1950) history of ¹⁴C in the atmosphere is very dramatic, normally ¹⁴C abundance is regulated by the fairly invariant flux of cosmic rays. Anyway, does that help? Or have I misunderstood? Cheers, --Plumbago 12:38, 29 March 2007 (UTC)

Critiques of a quasi sci-fi chapter by a non-scientist don't belong in an article about the application of scientific knowledge to a dating technique. The Russian author's minority of one opinion is not based in sound current scientific knowledge. Most effects listed above are taken care of by the calibration techniques in use, at least within the physical and statistical uncertainties of the datings. Notice that this article is about a technique. The generation and fate of radiocarbon in different reservoirs should be topics in the carbon-14 article, not in the one about dating techniques. Jclerman 15:13, 29 March 2007 (UTC)

Well yes, what you say should be in the article in some way. Nikola 15:04, 29 March 2007 (UTC)

Actually, Fomenko is a scientist, and he cites opinion of other scientists. Nikola 15:39, 29 March 2007 (UTC)

Sorry to disagree. He is a mathematician and mathematics is not a science. Concerning the relevance, currency, and his (or his translator's) understanding of the citations I and others have expressed our opinions in the preceding discussions. Jclerman 21:19, 29 March 2007 (UTC)

Yours is a very good WIKI article, but here's the Russian snag: look up "History:Fiction or Science?", vol.1, 2913621074, pp.74-80, 'Are radiocarbon datings to be trusted?" by Dr Prof Fomenko, this one can be labelled as somewhat literary exploit of a mathematician non-scientist(?!), and one on pp.80-90, "Critical analysis of hypothesis on which the radiocarbon method is based", by Dr Prof Mischenko, a high grade physicist, his report coincides 100% with tenets of WIKI article, but then he goes further and points to further factors that produce deviation; his verdict on precision of radiocarbon dating is: '..the radiocarbon method in its current state has deviation rate of 1000-2000 years for the specimens whose estimated age is less then 1000 years..'. The method does not or cannot take into account for samples taken: latitude, longtitude, proximity to certain geological formation on dry land, in the ocean,altitude,climate. The practice of submitting of samples with datings pre-estimated by archeaologists is vicious circle. This is why c14 method dismally fails all black box testing. Alas, they are certainly not creationists.86.199.104.80 08:15, 14 April 2007 (UTC)

Poggio Bracciolini

Deja vu reiterated. Your cited page 80 states that A.S. Mischenko is not a practicing physicist but a topologist and differential geometrist and expert in other similar mathematical specialties, which are quite removed from the sciences based in experimental verification and evidence. His comments based on Libby's (cf page 80)[6] radiocarbon dating are as good and current as mine would be if I would comment on his topological works basing my (a non-mathematician) arguments on Euclides rather than on Poincare. I strongly suggest you read a few paragraphs above this one my reference to the Nobel Symposium volumen on radiocarbon variations (ca 1970). Then apply the acquired knowledge to understand the later publications and in particular how the calibrations bypass the reservoir effects. True, Fomenko and Mischenko might not be creationists, but they are not scientists either. Jclerman 09:55, 14 April 2007 (UTC)

Dr Prof A.Fomenko happens to be a Full member of Russian(FSU) Academy of Sciences. The Russians were crazy to elect a non-scientist to this select body. Had a look at your ref. Conclusion:

QUOTE We did this by obtaining samples of acacia wood from the base of fortresses built during the reign of Sesostris III. UNQUOTE So, one takes a sample with prescribed (purely hypothetical) age of 3300 BC, calibrates the very sensitive c14 method which may deviate +/- m% for n-reasons to get a result of 3300 +/-50 years, and says we don't need reservoir C14 anymore. Genuflect at sight! Are You sure that the said fortress was built 3300 BC and not in 300BC or 300AD or 1300 AD? Vicious circle.

Poggio81.250.195.16 —The preceding unsigned comment was added by 81.250.195.16 (talk) 18:22, 15 April 2007 (UTC).

Go to the section About calibration, above in this page, i.e. here:Talk:Radiocarbon dating#About calibration. Jclerman 00:01, 16 April 2007 (UTC)

Paid a visit. Conclusion:

Mariage of Mr Carbon and alleged virgin Ms Dendra was made made in the heavens of egyptology, whereby the officiating priests have forgotten to tell Mr Carbon about Ms Dendra's immaculate baby of unknown age(up to 4000 years). Consequently c14 dating method calibrated on 'ancient' egyptian wood has an inbuilt error of the same unknown age + age of the tree (wood). Valid reason for divorce. It looks that the technically perfect edifice of c14 dating is built on arbitrary age ideas of samples given by egyptologists like acacia stump from foundation of a fortress of the pharaoh Sesotris III (3300 B.C.). Vicious circle. Is logic a non-science too? Captive fans go back to c14 reservoir.81.250.195.16 09:29, 16 April 2007 (UTC)Poggio

Deja vu reiterated again. Logic and math are formal disciplines which are quite removed from science-based experimental verifications. And Fomenko et al comments based on Libby's (cf page 80)[7] are currently irrelevant since Libby's radiocarbon dating publications have been superseded several decades ago. I strongly suggest that you read (in a few paragraphs above this one) my reference to the Nobel Symposium volumen on radiocarbon variations (ca 1970) and the extensive literature about the current calibrations which are NOT based on Egyptian chronologies but reach 45,000 years before present. Then you will understand why the reservoir discussions are irrelevant with respect to the current calibrated datings. Jclerman 16:55, 17 April 2007 (UTC)

mr Jclerman,

i am most concerned with your religious attitude towards carbon dating. i don't believe in god or in the bible or in creation of any sort, and i don't agree with fomenko, but i also don't agree with carbon dating and dendrochronology and this does not make me ignorant or dumb. please be more objective and add a section with scandals and failures about the carbon 14 dating method. if science depended on people who took science for granted, humanity would stagnate into centuries of nothing. you need to be more objective or someone else needs to come and work on this article. A. Guzman. Posted on 21:16, April 21, by User:72.225.251.14.

Accusing people of possessing religious attitudes towards science exhibits a lack of understanding of either religion or science. In my experience such attacks are done by religious zealots pretending to be rational. Nino 203.202.120.164 07:46, 5 August 2007 (UTC)

You and others are welcome to add sections to this discussion and/or the article. but you'll have to provide sources for your disbeliefs in carbon dating and in dendrochronology. Your comments about the scientific methodology belong to an epistemology article and/or discussion while your concerns about personal attitudes belong nowhere. Jclerman 05:37, 22 April 2007 (UTC)

General references/further reading

References (general or specific) which were used prior to the development of the Wiki cite system should be kept within the reference section rather than relegated to a further reading section. If, by going back through the article history, a specific reference is found to not be supportive of the article writing then it can be relegated to a further reading section or removed (if not relevant). References supporting a specific portion of the article should be cited therein. But general references are important - per that - removing the further reading header pending evidence. Vsmith 11:53, 27 February 2007 (UTC)

Cool. I didn't want to remove them, but was just concerned that their relationship to the article's text wasn't clear enough. If a reader can't work out what a particular source is for (e.g. the one about ¹⁴C on Titan) then it should either be written explicitly into the text, or removed to minimise clutter. I'm pretty sure that all of the cites in the article can be written in, and those that are of a more background nature could even be identified within the main text as such ("There are many good overviews of this subject^{[1] [2] [3]}."). It might just be my background as a scientist, but I can't abide by dangling references that aren't cited in the text! Anyway, I'll try to write them in myself. --Plumbago 12:07, 27 February 2007 (UTC)

material for writng "controversy" article.

Here is a list of articles on "controversy" of C14 dating. This is not necessary a scientific view, but only a list of material that may be included when starting a controversy section / article --- so, please don't argue.

1. New Chronology (Fomenko) -- new chronology, pseudohistory.
2. Young Earth creationism -- Biblical POV.
3. ... (please add more item)) ...

-- 219.78.109.166 15:27, 3 May 2007 (UTC)

Hmmmm. You may be wasting your time here. As the discussion above indicates, there really is no "controversy" as such. In scientific circles there are disagreements about dating protocols and subtleties in interpretation, but these are partially covered in the article as stands. Outside of science, the "controversy" has more to do with any method for dating the Earth, and not specifically with ¹⁴C. If you disagree, you might like to provide us with more than just a few links to other articles. Cheers, --Plumbago 16:15, 3 May 2007 (UTC)

I agree with Plumbago. User 219.*.*.* seems not to have read or understood the discussions of both Creationism and Fomenkism in the preceding sections and in the article(s) relevant to carbon-14, dendrochronology, and other dating techniques. Jclerman 17:17, 3 May 2007 (UTC)

Why make political an article thats strictly scientific?

Because some may argue that it is scientifically incorrect.12.157.120.212 (talk) 07:59, 6 December 2008 (UTC)

C14 in Coal

An explanation for this in the article might be appropriate. Unauthoritative online discussion I've seen attributes it to U and Th in the coal. — Preceding unsigned comment added by 75.4.225.143 (talk) 17:39, 15 July 2007 (UTC)

Wrong nuclear reactions in basic physics section

According to definition of nuclear reaction, both nuclear reactions in the article are incorrect. Both has wrong balance in mass numbers, so it breaks conservation law of baryon number. The first equation is missing one neutron on right side, the second is missing one on the left side. Charges are in balance. Antineutrino, seems to be natural by-product of beta decay of neutron, the neutron, which is probably missing on left side. Please, fix this (anybody who knows better). I am sorry, I do not know the right reaction. The same mistake seem to be also in carbon-14 article.[striked-through by the author] 147.231.12.9 14:11, 16 August 2007 (UTC)

I realise I'm about to reveal my ignorance here, but let's look at this:

$n+\mathrm {~_{7}^{14}N} \rightarrow \mathrm {~_{6}^{14}C} +p$

Left-hand side has 8 neutrons (1 extranuclear) and 7 protons. Right-hand side has 8 neutrons and 7 protons (1 extranuclear). That seems to balance, but I can well imagine that it's a simplified form and that it's omiting low/zero mass particles. Can you explain further?

$\mathrm {~_{6}^{14}C} \rightarrow \mathrm {~_{7}^{14}N} +e^{-}+{\bar {\nu }}_{e}$

This one's trickier for me since it has a subatomic particle, ${\bar {\nu }}_{e}$, that I don't know much about. But it otherwise all balances up in terms of protons, neutrons and electrons. Although it's very small, the antineutrino has mass, is this the unbalanced bit you're referring to? Or am I missing something? Cheers, --Plumbago 14:25, 16 August 2007 (UTC)

Sorry, it is my ignorance, thank you. Should I should delete this section, if I know it is wrong? 147.231.12.9 14:41, 16 August 2007 (UTC)

Actually, I'd leave it here. I might be wrong after all! Maybe another editor can check my sums. --Plumbago 16:12, 16 August 2007 (UTC)

I don't think so. Unfortunately, I made mistake. O.K. let's remove it as soon as it is checked by the third person (I have removed my comment in discussion under carbon-14). 147.231.12.9 09:11, 17 August 2007 (UTC)

General information in the posting

While I appreciated the technical nature of the Radiocarbon dating entry, we were trying to use wikipedia in a more general sense. For instance: Is carbon dating for living things only or for inanimate objects also? How does carbon dating date foot prints? I don't know the answer to these questions and would like to know.

Kkayaker 16:47, 14 September 2007 (UTC)kkayaker

Carbon dating is for dead things that used to be living, and cannot, to my knowledge, be used to date footprints.80.235.60.123 (talk) 13:50, 29 October 2008 (UTC)

You are presumably refering to the Ancient footprints of Acahualinca link in the see also section. According to the article on the footprints, they "dated the sand directly under the footprints" to get an earliest date (I'm not sure how this was done, but there was probably organic matter in the sand). Inanimate objects can be indirectly dated through radiocarbon dating: if an object is found in a layer, or sandwiched between two layers, the dates from the layers can give an approximate date for the object. Nev1 (talk) 13:56, 29 October 2008 (UTC)

Status in scientific community

Hello,

I would like to know if there is a consensus in the scientific community on the matter of radiocarbon dating, or if vast majority of scientists stands behind the method or if there are any ongoing disputes in the scientific community; this method seems to be disputed from certain circles outside the scientific community at least, but I have hoped to get to know about whether any well-known scientists agree with the arguments (or indeed what the arguments really are).

Unfortunately, the scale of the discussion page is quite intimidating, so I have to admit I didn't really read it all. I have spotted a reference to WP:FRINGE and I agree, but I still believe that there should be some note about this in the article, even if it runs like

"There is consensus in the scientific community about this method's accuracy and it is regularly used in archeology and history science. The theory has been disputed outside of the scientific circles, see Random Article."

(Note that I have no idea if this is true - that's what I hoped to find out in the first place.)

Thank you, Pasky (talk) 01:49, 29 December 2007 (UTC)

Please read the comments above, start with Plumbago and Jclerman's responses from last May. Basically - "been there, done that" repeatedly. Vsmith (talk) 03:03, 29 December 2007 (UTC)

Accuracy of Radiocarbon dating (again)

After a quick read through the article, the only statement of the accuracy of radiocarbon dates I found was that their accuracy has increased "since 1962, when they were accurate to 700 years at worst."

I recognize the variation of the accuracy with sample size and position on the irregularly shaped calibration curve, but a well-documented statement of the accuracies routinely obtained within various periods would be helpful and would do much to silence the critics. Does anyone know of a recent source with a table (or graph) showing such accuracy at various historical periods?

--SteveMcCluskey (talk) 15:30, 29 December 2007 (UTC)

I found it! The Radiocarbon web page has the radiocarbon calibration curve going back to 26,000 years BP. The dating error from the calibration curve does not exceed ±16 years for the historic and late prehistoric period (less than 6,000 yrs BP) and does not exceed ±163 years over the entire 26,000 years of the curve. --SteveMcCluskey (talk) 03:01, 30 December 2007 (UTC)

After some thought and careful reading of the cited article, I realized that the calibration curve's accuracy is better -- probably much better -- than the results of any single measurement. As I mentioned above, what we still need is "a well-documented statement of the accuracies routinely obtained within various periods." --SteveMcCluskey (talk) 14:50, 30 December 2007 (UTC)

You may try this: SYSTEMATIC INVESTIGATION OF UNCERTAINTIES IN RADIOCARBON DATING DUE TO FLUCTUATIONS IN THE CALIBRATION CURVE Author(s): NIKLAUS TR, BONANI G, SUTER M, et al. Source: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS Volume: 92 Issue: 1-4 Pages: 194-200 Published: 1994 A little old, but I think the conclusions are still valid. I think that this is also the reason that there is no more recent, comprehensive evaluation. Peter.steier (talk) 18:07, 10 February 2008 (UTC)

Peter,

Thanks for the reference; unfortunately it's not in our library here and the only citation I found to it was your nice 2004 article in Radiocarbon, which deals with precision, not accuracy.

Whenever you have time could you briefly summarize the results of Niklaus et al. in the article. It would fill a significant gap. --SteveMcCluskey (talk) 19:44, 10 February 2008 (UTC)

I obtained a copy of Niklaus et al., and added a few lines summarizing what they have to say about the effects of the calibration curve on dating accuracy. --SteveMcCluskey (talk) 22:00, 25 February 2008 (UTC)

Inorganic material

Could someone, please, confirm if it is possible to make radiocarbon test on inorganic material? Thanks in advance. --Tonyjeff (talk) 13:55, 8 January 2008 (UTC)

Would diamonds be acceptable as inorganic? See reference 4 in the article Dan Watts (talk) 14:01, 8 January 2008 (UTC)

Mortar can be perceived both as an inorganic and organic substance, organic because when the mortar hardens, the current surrounding atmosphere is encased in the substance. Just added a section in the mortar article on these fairly new methods/findings. 88.148.204.5 (talk) 17:21, 14 January 2008 (UTC)

Not an organic substance, it's more of an unintentional atmospheric sampling mechanism. And you might want to change the Mortar link to point at your intended meaning of the word. -- SEWilco (talk) 17:33, 14 January 2008 (UTC)

A thousand apologies for not pipering it ;) Done now. As for the organic/inorganic thingy, please excuse me for not having English as my native language. You are correct that it is not in itself organic, though as far as analyzing the material by means of radiocarbon dating, it may be regarded as such due to the presence of measurable data. 88.148.204.5 (talk) 21:58, 14 January 2008 (UTC)

No. Personal perceptions and linguistics don't make it organic. And it doesn't need to be organic to be radiocarbon dated. And the data are not measured but the result of measurements, that is if my perceptions of y your perceptions of the meaning of data are correct ;-) Perhaps you should called "trapped CO2". Check the nomenclature for CO2 bubbles found in ice cores. Jclerman (talk) 22:12, 14 January 2008 (UTC)

I stand corrected. Please do add more info about the issue in various articles you see fit, should the method be found notable enough for more exposure on WP. 88.148.204.5 (talk) 13:41, 15 January 2008 (UTC)

A minor quibble with Jclerman's suggestion of calling it "trapped CO2". In ice cores the bubbles of atmospheric CO₂ are physically trapped in the freezing ice; in the case of mortar the atmospheric CO₂ is chemically included in the mortar when quicklime (CaOH) is chemically converted into CaCO₃. (I hope I have my chemistry straight here). If I recall the ice core studies correctly, they are more concerned with the balance between the two stable isotopes ¹²C and ¹³C as a proxy for temperature, rather than with ¹⁴C and dating.

I think the proxy for temp was the oxygen isotope ratio while the carbon isotope ratios were used to date the samples and to normalize the radiocarbon content to the normal stable carbon isotopes ratio. Jclerman (talk) 15:14, 16 January 2008 (UTC)

I think dating by atmospheric CO₂ preserved in inorganic materials deserves to be included in the article (perhaps as a subsection). --SteveMcCluskey (talk) 15:10, 15 January 2008 (UTC)

Sounds like a good idea for someone who finds some sources to mention it. -- SEWilco (talk) 16:35, 15 January 2008 (UTC)

After taking a further look at the article, I realized that while it seems very good on the physics of the problem, it says little about its archaeological aspects. A section on the issues involved in sampling carbonaceous materials from archaeological sites seems to be in order. --SteveMcCluskey (talk) 17:18, 15 January 2008 (UTC)

Feel free to write the sections you propose above. Jclerman (talk) 15:14, 16 January 2008 (UTC)

OK, I'll open a section, but it will only be a stub; I hope some people who really know archaeology can add to it. --SteveMcCluskey (talk) 15:26, 16 January 2008 (UTC)

Accuracy?

Hi. I'm about to add this to a piece of work, but it needs verufying, and I don't know where else to go for people who know about carbon dating: carbon-14 dates were only accurate within one thousand years, plus or minus, and so a rapid [climate] change, within 10 years, say, would have been undetectable. St91 (talk) 19:31, 26 February 2008 (UTC)

I recently added a few lines dealing with accuracy to the article and, depending on where the dates are in the calibration curve, the maximum uncertainty (measured as the range of probable dates) is about 800 years, improving to an uncertainty of about 113 years in more well-behaved regions of the calibration curve. This, of course, refers to the accuracy of calibrated calendar dates. The precision of non-calibrated radiocarbon dates would be higher than that.

Your claim of accuracy of only one thousand years exaggerates the uncertainty, although your statement that a ten year change is not detectable sounds right. It would be better if you can cite a source to back up your inference, otherwise you are coming close to Original Research. --SteveMcCluskey (talk) 20:40, 26 February 2008 (UTC)

unreliable reference

I have reverted this change to remove the reference to Anatoly Fomenko's work, which is widely criticized as pseudoscience. --SteveMcCluskey (talk) 16:18, 27 February 2008 (UTC)

Fossils

Carbon dating is useless for mineralized fossils, right? Tempshill (talk) 19:14, 27 February 2008 (UTC)

Yes, carbon dating only goes back about 50000 years, but there are many other elements that also radioactively decay and can be used for dating, see Radiometric dating. I believe some of these particles can date back to around a billion years. --Dacium (talk) 03:14, 7 March 2008 (UTC)

Sorry, I should have been more clear. Carbon dating is useless for mineralized fossils because the organic material has been replaced by minerals, regardless of the age of the fossil; correct? Thanks in advance - Tempshill (talk) 17:48, 13 March 2008 (UTC)

It also probably won't be done for Tyrannosaurus (although for non-scientific reasons). Dan Watts (talk) 21:22, 13 March 2008 (UTC)

Accurate to 60,000 years?

If it can only determine age "up to 60,000 years", how do we use it for the age of fossils which are supposedly tens or hundreds of millions of years old? —Preceding unsigned comment added by Lordofthemarsh (talk • contribs) 17:34, 12 April 2008 (UTC)

Radiocarbon dating can't be used to date anything older than about 60,000 years. Unless there is a technique that I'm unaware of (perfectly possible, it's not my field) the absolute dating of older fossils cannot be done directly. Radiometric dating can however be used to calibrate a stratigraphic framework built up using fossils by directly dating extrusive volcanic rocks found within the same sequence. Mikenorton (talk) 18:00, 12 April 2008 (UTC)

transferred from the article for clarification

¹⁴C behaves slightly ¹²C and ¹³C (due to different atomic mass), such that the isotopes will be involved in reactions out of ratio . This so called "fractionation" can however be reliable corrected with the assumption that the fractionation of 14C and 12C is twice the fractionation of the stable isotopes 13C and 12C. -- —Preceding unsigned comment added by Jclerman (talk • contribs) 03:15, 23 May 2008

Just look at the changes during the recent flurry of edits. (diff) The original phrasing is near the end of the diff, on the left side. I don't know why it was moved up there, but a binary search in the changes can reveal which change introduced it unless you prefer riffling through the sequence. -- SEWilco (talk) 04:19, 23 May 2008 (UTC)

Why shall I do that? As I commented on the article edits, the transferred paragraph (above) contains "few of the several obscure, incomplete, and/or incorrect statements" found in the article. It was transferred here either to be re-cast or to remain deleted. Jclerman (talk) 10:57, 23 May 2008 (UTC).

Also, somebody lost Fomenko's reference while Fomenko's article refers to this article critique of Fomenko's critique. As I said before, "Please be consistent and try not to increase the entropy. TIA" Jclerman (talk) 10:57, 23 May 2008 (UTC)

whole section to be corrected or to remain deleted

Sample selection

 ? My comment. NO! This article is not a lab manual, as it was earlier and extensively discussed. A shorter and correct text would be wiser than the edited text.

The whole section has been transferred here to be corrected and recast until acceptable or to remain deleted. Jclerman (talk) 11:27, 23 May 2008 (UTC)

Materials for radiocarb*on dating are commonly uncovered through archaeological excavations. Common examples of carbonaceous materials include wood used in buildings and charcoal from fires, which incorporate atmospheric carbon dioxide from the time the wood was growing, human bones, residues of food (stored plant remains and bones from animals), clothing, and more recently, mortar which incorporates atmospheric carbon dioxide from the time that the mortar set.. Selection of suitable samples and good sampling practice is essential to obtain useful dating results. The link between the formation of the sample and the event to be dated has to be clearly established. Error is likely to arise e.g. from dating wood from the center of the trunk of a tree. Such old wood, turned into an artifact some time after the death of the tree, will reflect the sprouting of the tree and not the event of carving. Thus, short-lived samples are preferable. Documentation of the precise archaeological context and the stratigraphy is essential for correlating a sample with an event. An olive stone in a destruction layer of a settlement may have been dropped there on the day of the destruction, it may have been lying around for a considerable time, and it may have fallen on the ruins of the city a considerable time later. Additionally, the destruction layer may have been disturbed by a waste-pite digged by a later cultural period, where the olive stone was dumped. Careful excavation practice can clarify these questions.

Collection of samples for radiocarbon dating should avoid contamination from a different time period. Usual handling is uncritical, since the samples are in most cases already heavily contaminated with surrounding soil, which is removed during sample preparation. However, often contamination arises from substances applied for conservational purposes or from adhesives used to lable the samples. This is especially the case for samples excavated in the past and stored in museums.

Various pretreatment techniques, including physical identification of specific portions of the sample and chemical separation to insure that only organic parts original to sample are included, have been developed to ensure the accuracy of the resulting dates.

Additional error is likely to arise from the nature and collection of the sample itself, e.g., a tree may accumulate carbon over a significant period of time. Such old wood, turned into an artifact some time after the death of the tree, will reflect the date of the carbon in the wood.

Temporarily removed by Jclerman (talk) 11:27, 23 May 2008 (UTC)

Measurements and scales (1)

From reference 7: "No age is reported greater than 60,000 years." How much clearer could their position be? Dan Watts (talk) 19:39, 26 May 2008 (UTC)

Much more, indeed. E.g., what does it mean "No age is reported"? Some readers would interpret it to mean no age of any material type and condition, other readers would interpret it to mean no age of >100my samples, others might interpret it to mean blanks, In one day or one week or one month analysis time? And which type of instrument? And more... Jclerman (talk) 13:37, 28 May 2008 (UTC)

Measurements and scales (2)

What does 'ages in excess of 100 my' mean in the last parag of this section:- <quote>"A variety of sample processing and instrument-based constraints have been postulated to explain the upper age-limit. To examine instrument-based background activities in the AMS instrument of the W. M. Keck Carbon Cycle Accelerator Mass Spectrometry Laboratory of the University of California, a set of natural diamonds were dated. Natural diamond samples from different sources within rock formations with standard geological ages in excess of 100 my yielded ¹⁴C apparent ages 64,920±430 BP to 80,000±1100 BP as reported in 2007[8]."<unquote> ??? --87.114.128.12 (talk) 11:41, 8 September 2008 (UTC)

It means that the sources examined, diamonds, were independently dated as being more than 100 million years in age ("my" is a frequently used abbreviation for million years). When they were ¹⁴C "dated" using the AMS instrument they reported ages of around 80,000 years. This is not a real age, but reflects the maximum age to which items that, in principle, contain ¹⁴C can be dated using current ¹⁴C techniques. The study in question was not interested in dating the diamonds at all (see the various quotations from it, and its authors, below), but was using them as a ¹⁴C-free source to establish the accuracy of the technique used, and to try to narrow down its sources of error. Hope this helps. Cheers, --PLUMBAGO 11:52, 8 September 2008 (UTC)

rv " for a 1 milligram sample of graphite,"

This and other statemetns regarding measurement interval, type of material, quantity of carbon in the sample, are important. Please, don't dilute the article. Jclerman (talk) 18:37, 27 May 2008 (UTC)

Please, discuss changes in this page.

Please, if you aren't familiar with the analytical techniques and/or their language, propose changes here rather than introducing them directly in the article. It will contribute to a smoother process than the current practice. TIA. Jclerman (talk) 18:42, 27 May 2008 (UTC)

From reference 7:

Limiting Ages

There are two situations that limit an age; the first is that the measured Fm
is smaller than that of the corresponding process blank measured in the same
suite of samples on the AMS. If this is the case, then the reported age will
be quoted as an age greater than the age of the process blank. No age is
reported greater than 60,000 years. The typical background age for organic
combustions is 48,000 years and for inorganic carbon samples, 52,000 years.

How does using this information dilute the article? Dan Watts (talk) 21:49, 27 May 2008 (UTC)

To re-cast such paragraph expanding with all the assumptions encapsulated in the cryptic "typical" one would need three pages of text, which would be OK for a how-to manual but not for an encyclopedia article. Furthermore, you'd need to xplain why only combusted organic carbon has a given limit date while not other forms of organic carbon. "And no age is reported" by whom? in general or by the authors of your quoted article? If you want a full critique, please post or email me a copy of the full article.

Making the major part ofthe article a dIscussion of the convoluted operations and auxiliary tests and measurements performed to obtain one date, would dilute the article's intention to give an encyclopedia-level description of the dating method. The readers that want to learn and critique all the intrincacies and delicacies of radiocarbon dating should scrutinize both the classic and the current references.

IMHO. Jclerman (talk) 23:04, 27 May 2008 (UTC)

My apologies. I did not realize that you had not read the reference which used the "1 milligram sample of graphite" information. The quote that I listed was from that same on-line article. You may see it here: http://www.nosams.whoi.edu/clients/data.html if you do not believe that I took the quote from them. Since the same reference had both statements (1 milligram .... and No age is reported ....) and the statement that I chose is a superset of the (unnecessarily?) limited statement that you chose, why should the quote currently shown be the proper choice? Dan Watts (talk) 02:05, 28 May 2008 (UTC)

Why did you, without discussion, decide to hide the fascinating information that researchers have concluded concerning ¹⁴C? Dan Watts (talk) 01:28, 28 May 2008 (UTC)

I think that some of your comments and questions have been answered in the next section, e.g. the one about the article/reference source (I meant the peer reviewed article cited in the reference, not the online web page). About HTML hidden sections or paragraphs, as explained (or not) elsewhere, they are not intended to be permanent supressions but temporary until recast or definitely deleted (I guess I "hid"several sectons/paragraphs in the article). Now it's my turn to apologize but I don't recall which is the fascinating information you refer to. In particular, I find everything related to radiocarbon and other environmental isotopes fascinating. Otherwise I wopuldn't have dedicated most of my life to them. However, my short term memory is bad enough (a side effect of aging) that I'd appreciate it if you transcribe the statements rather than referring to them indirectly as, e.g., "the deleted quote". In particular, I might have deleted or modified several and, yes, I migth have done some of them mistakenly. Jclerman (talk) 13:59, 28 May 2008 (UTC)

And now it is my turn to apologize. I wrote my comment on the "fascinating information" before I noticed your section containing the quote in question below. Let's continue the discussion there. Dan Watts (talk) 14:54, 28 May 2008 (UTC)

to recast - messy backgrounds & theories

Temporarily transferred from the article:

In contrast to the sample processing and instrument-based background theories, the authors of an AMS instrument background study conclude: "¹⁴C from the actual sample is probably the dominant component of the 'routine' background." .

Jclerman (talk) 22:32, 27 May 2008 (UTC)

Is this too messy for the reader? Are such facts not for the reader to know? Why remove the reference? Dan Watts (talk) 01:58, 28 May 2008 (UTC)

Nothing has been removed permanently, only until somebody recasts the paragraph as to be understood by the average encyclopedia reader rather than by "ïnsiders". It is unclear what are a sample and a background, what are the theories mentioned, what are the less dominant components of the "routine background". what is the significance for datings of the limit max apparent age of a blank, is there a description of blanks & backgrounds ?). is there a description of such background and blank samples in the wiki article? If a milligram amount is mentioned, why no measurement time and age are mentioned? &tc.

IMHO, lacking a language editor (as those that printed encyclopedias have) allows for a messy increase of the text entropy after several individual text changes, insertions, and deletions. And such problems are compounded when quoting from web pages that are also affected by lack of peer and/or language review.

Jclerman (talk) 12:53, 28 May 2008 (UTC)

Would this be more direct and just as accurate?

In contrast to the sample processing and instrument-based background theories, the authors of an AMS instrument background study conclude that most of the ¹⁴C which derives its age comes from the sample itself .

Dan Watts (talk) 00:35, 2 June 2008 (UTC)

I'll comment, annotate, etc in a couple days, after taking care of some urgent hardware problems. Jclerman (talk) 22:43, 28 May 2008 (UTC)

It doesn't explain what is meant by background. Instrument background? an old sample used as bacground?

The background is described in the paper that I e-mailed you under separate cover. I can attempt to describe it in the article if that would be of some utility. Dan Watts (talk) 02:00, 3 June 2008 (UTC)

Sorry but I have to be terse. I'm still experiencing hardware and software problems that I have to solve myself.

I don't understand the statement about the age limit, quoted (as far as I can guess) from a non-peer reviewed web page. I summarize below how I (and many others) calculated and reported ages of samples at the max limit.

A sample's activity is indistinguishable from the activity of a background sample when its activity is within 2 standard deviations of the activity obtained from a sample which contains no radiocarbon. Tis value, i.e. 2 times the activity of a sample depleted from C-14, inputed as gthe activity in the age equation gives the maximum age limit.

If it happens that for certain laboratory, instrument, type of sample, amount of carbon in the sample, detection time, etc, such computed maximum age limit is 60,000 years, we express the result of dating a sample with such an activity as dating ">60,000 yrs BP" (i.e. older than 60,000 years).

If, for the same lab, etc, of the preceding example, one decides not to report "older than 60,000 ages"), how would one report dates derived from activities that compute to 59,000 ?

One couldn't. This should be ovious to you after you assume some sample activities and perform the corresponding calculations.

Jclerman (talk) 22:10, 2 June 2008 (UTC)

I do not know their reasons, I was reporting what is verifiable. Dan Watts (talk) 02:00, 3 June 2008 (UTC)

Why would a quote from a research article on ¹⁴C be out of place? Dan Watts (talk) 13:17, 4 June 2008 (UTC)

I'm coming to this a bit late, so forgive me if I misunderstand here. The quotation (which is currently commented out) is from the introduction of the paper, and is not obviously a conclusion from it. Correct me if I'm wrong, but I (skim-)read the paper as a rather technical discussion to narrow down the error in ¹⁴C measurements (hence the use of 1. very old diamond; 2. pieces taken from the same diamond). Ultimately, the authors are aiming to develop a technique that might let them age samples to order 10⁵ years (they suggest creating synthetic diamond films from samples for ¹⁴C analysis). To me, the quotation appears to misrepresent the paper's aims, and is not placed in a sufficiently clear context for a reader to follow. What, exactly, is the article trying to say on this point? Cheers, --Plumbago (talk) 13:45, 4 June 2008 (UTC)

From a fast reading of the papaer, the authors found that the currents detected by the AMS for diamonds (which are gelogically far beyond the radiocadrbon dating range) were lower than those for other materials. Thus they propose to synthesize diamonds from the samples to be dated. Such procedure would extend the current AMS dating range. By no means the quoted dates should be considered diamond dates. They are called apparent because they are not dating an undatable sample. It is the AMS currents that are of relevance to compute the maximum limit age (see, above, statement on the two standard deviations to determine the older than limit). It is a classical metrological problem, unfortunately poorly summarized in the paper's abstract. Jclerman (talk) 18:40, 4 June 2008 (UTC)

Yup, I'd go with that. And I'd second your opinion about the abstract - the referees who reviewed this paper did it no favours letting this slip past (that, and the paper has no clearly stated conclusions). Cheers, --Plumbago (talk) 07:45, 5 June 2008 (UTC)

Congratulations for your sharp insight. Also notice that the paper was not published by a radiocarbon dating journal in which the reviewers would have posed the questions you raise. For such a "measurement techniques jouirnal" the article reviewers should have requested the authors to fully re-write the article from the point of view of signal/noise ratio analysis, or to add a section with such an approach. Now, how do you suggest this info should be included in the wiki article within the wiki policies re verifiability and others? Jclerman (talk) 13:28, 5 June 2008 (UTC)

So:

1) The paper stated what is currently held in limbo on the article.

2) The measurements are consistent with a radiocarbon age which is untenable (to some understanding of geology)

3) The authors are to be censured (how dare they report such facts)?

I think that I will let someone else try to do justice with these (verifiable) facts. Dan Watts (talk) 01:28, 7 June 2008 (UTC)

Dan, please read the above statements more carefully. The "censured" text labels itself as the paper's conclusions - which is patently incorrect. It would be more accurate to say that "the authors note", but that: (a) is a rather weak statement to include in an encyclopedia article; (b) could be argued as a poor use of the paper as a source; and (c) still leaves unanswered the point of adding this text. What does "¹⁴C from the actual sample is probably the dominant component of the 'routine' background" actually mean (i.e. could it be paraphrased for clarity?), and how does it help in the context here? I asked this above, but still await an answer.

Furthermore, the paper has nothing to do with using radiocarbon to establish the age of the diamonds (that's already known approximately from stratigraphy and other radioisotopes). It has everything to do with developing a new technique for radiocarbon measurement that is superior (= allows us to reach further back in time) than those used at present. This paper does not represent a criticism of radiocarbon dating (as you seem to be implying above: "radiocarbon age which is untenable"), and I'm sure the authors would be appalled/amused at the notion that it could be read that way.

And I've no idea where you got "how dare they report such facts?" from. Bar it having a somewhat slack abstract and omitting conclusions, there's absolutely nothing wrong with the paper. The way to include it in the article is to report what the authors did: they tried to establish a methodology for measuring older samples that, hitherto, have their ¹⁴C signals lost in the noise of inferior techniques. That would convey to the reader that radiocarbon dating is a living field in which methodologies are constantly being improved to allow us to date samples both more accurately and when they are older. As the technique is well-established, and relatively well-known (almost everyone has heard of it, even if they haven't heard of other radioisotope dating methods), this could be an important addition to the article. Cheers, --Plumbago (talk) 07:18, 7 June 2008 (UTC)

The measurements were reported, and therefore can be used to estimate a radiocarbon age (which they did). That "age" clearly contrasts with a stratigraphic determination. The meaning of their statement (as I understand it) is: the ¹⁴C that was measured came from the diamond samples. It did not come from instrument background, handling, or sample preparation. It was in situ. I got the "how dare they" from the (current) removal of their statement. Dan Watts (talk) 13:11, 7 June 2008 (UTC)

Hi Dan, sorry for the delay in getting back to you. I'm still not sure that we've got to the bottom of this. The paper's authors precede the quotation under discussion with a reference to:

"On this basis, we propose that we have eliminated the major sources of mass 14 ion with the exception of that contributed from various components of instrument or machine background signal and perhaps that contributed from the sample holder itself"

Which suggests that an unquantified proportion of the ¹⁴C may be foreign to the sampled diamonds. Of course, the authors then go on to suggest in the disputed quotation that ¹⁴C from the sample is the (unquantified) dominant portion of the measured ¹⁴C signal, although they qualify this with a cryptic (to me anyway) mention of "'routine' background" (their quotes).

Since I have only a passing familiarity with ¹⁴C and may have gotten completely the wrong end of the sick here, I've e-mailed the lead author of the paper to request clarification of this point. Most likely, the explanation lies within the paper already, but I'm simply unable to understand it. Anyway, since the paper makes no claims to the effect that the measurements described overturn the entire field of ¹⁴C dating, I expect that this will confirm what "'routine'" means here. Best regards, --Plumbago (talk) 17:25, 11 June 2008 (UTC)

Sorry for the delay. I've been working on the draft of the following comments intermittently between medical appointments to mitigate previous medical errors.

Here are my comments:

1. Dating?

The authors didn't intent to date the diamonds but to study the contributions to the background by the machine, the diverse chemical and physical procedures, and the sample materials. In fact, they did convert the results of their measurements (ion currents) first to percent modern carbon (pmc) and later to equivalent radiocarbon age. Notice that they called such converted data an apparent age. And they did so not less than nine times in the article that we are discussing. These dates are qualified as apparent. I believe that it is because they are translated from pmc to equivalent kyrs without subtracting a background value from the pmc results (i.e. they assume a perhaps unrealistic nul virtual background) . The results of the analyses, IMHO indicate which is the limit of detection in pmc. The lowest pmc that can be detected with confidence has to be higher than the limit of detection, thus the maximum limit age for the AMS instrument in discusion has to be lower than the apparent ages published for this particular instrument. As a reminder, AMS doesn't measure ages. It measures signals in a mass collector tuned to mass 14. These are not fully and necessarily generated by C14 atoms. From the "14 signal" radiocarbon ages are inferred on basis of a series of assumptions. Metrologically speaking, measurements near the limits of detection are very difficult if not practically impossible. And the closer they approach this limit the more controversial they become in the eyes of the "litigating parties". The courts of law are full of DUI cases in which from a chemical analysis it's inferred whether the defendant was or not affected by alcohol. Due to such misunderstandings of the impossibility of measuring zero concentrations the US Congress has passed laws establishing the acceptable content of carcinogens in food, air, etc, as an impossible "zero" concentration. One can only assert that a concentration is "lower than the detection limit". In the case of radiocarbon ages, a "zero measurement" of decaying atoms or of "buckett 14" collector would be inferred as "infinite age". As these are not realizable, limit ages are stated as "greater than xxx BP". Near this limit the uncertainties become necessarily asymmetric. The + larger in absolute value than the -, as correctly shown in the Finnish paper referred to below. Also metrologically and in a short summary, an instrument that doesn't show noise when measuring a blanck, is not sensitive enough. Despite the metrological hortcommings of the article by Taylor and coworker, I essentially believe the numerical values and trust the chemical and physical manipulations that led to them.

2. Domination?

Taylor and coworker state:

14C from the actual sample is probably the dominant component of the ‘‘routine’’ background.

The expression probably the dominant

component conveys the idea that they don't believe that all the signal is due to radiocarbon in the diamonds but only part of it. Amongst other possible components they state that the variability of the signal suggests it being due possibly to microfractures in individual diamonds. Lacking a more precise statement I assume the conservative practice for such cases and believe it means above 50% being the remainder "instrument background". The authors fail to make a connection between the origin of the dominant fraction and the microfractures mentioned. Do they mean instrumental and/or environmental C14 adsorbed in the microfractures? I don't know. I'm glad the authors have been contacted and hope they will clarify this aspect of their paper.

3. Last but not least:

I fully agree with Dan [User:Wdanwatts]. He said, above:

I think that I will let someone else try to do justice with these (verifiable) facts.

I expected that notwistanding the short time lapsed since Taylor and coworker's article was published, others have already described related

experiences and critiques. I found a researcher that tried to replicate and/or discuss the results of Taylor and coworker. A few months ago Vesa Palonen authored a Ph.D. Dissertation about AMS and data analysis (Jan. 2008, Univ. of Helsinki). It is available online here [8] if by any reason you can't get it, I can email you a copy of the pdf file that I downloaded. Warning, it is 70 pages long and from a brief glance at the table of contents and tables of results it appears that 1/3 of it might be relevant to our ongoing discussion.

4. Disclaimer:

My direct experimental experience and expertise is about 10 yrs doing C14 analyses by proportional counting, both for geochemical research (CO2), and latitudinal dependent calibrations of the C14 scale. and for applied dating. I have done no experimental work using an AMS instrument. I did spend about another decade doing and interpreting mass-spectrometric analyses of stable isotopes of C and O in plant and animal tissues for studies of photosynthetic types (C3, C4, CAM), food chains, etc. Thus, my opinions might be subliminally biased. Thus I highly value your "outsider" contributions to this fascinating discussion. I don't understand which is the origin of the real and apparent C14 measured by Taylor and coworker and by the Finnish group. I don't believe that they dated diamonds. They don't either, otherwise they would state it so. But I firmly believe that such lack of understanding of the origin of such C14 does not invalidate by any means the dating method and the dates inferred from measurements which lie 2 standard deviations above "instrument+chemistry+physics backgrounds".

Kind regards, JC Jclerman (talk) 08:53, 12 June 2008 (UTC)

AMS study

Further to the above, a much belated response. My fault primarily. Anyway, the information that I got back from the lead author of this study was as follows ...

“ The point of using diamonds for this experiment was that obviously (1) they are geologically very old material and would thus be expected to have no measurable radiocarbon IF there has been no in situ production or contamination, (2) they can be used directly in the ion source (i.e., we don’t have to do any chemistry on them), and (3) they should give a reasonable carbon beam in the ion source.

We were trying to determine something about the real machine background which would be dominated by the level of ion source crosstalk, i.e., how much of one sample remain in the ion source after another is being measured. As the paper explains it, for the current Keck UCI machine, the bottom is on the order of .005 pMC (% modern carbon) or the equivalent of about 80,000 years. Using our diamonds in their ion source, approximately the same number was generated by another much larger machine that have some additional instrument features that can detect more efficiently pseudo-14C ions at the detector, so we assume that we are seeing something that is reflecting the characteristic of the current generation of ion sources used in AMS systems.

”

As I understand this, the seemingly anomalous 80,000 year signal is actually the result of carbon from previous analyses contaminating the machine. Or something like that (I don't entirely follow the use of "ion source" here). Anyway, I hope that this clears up this issue, or that we can at least agree that the diamond results are not Earth chronology shattering. Cheers, --PLUMBAGO 14:53, 15 August 2008 (UTC)

As I understand it, another laboratory also got the same level of 14C from measuring diamonds "Using our diamonds in their ion source, approximately the same number was generated ...." I don't see the imprecision or misleadingness of the quote that I reintroduced. Dan Watts (talk) 14:57, 28 August 2008 (UTC)

The quote in the text is ...

“ ¹⁴C from the actual sample is probably the dominant component of the 'routine' background ”

Now, I'd argue that this is somewhat ambiguous since the word "routine" is in quotation marks, suggesting that is has some meaning that is alluded to outside of the quoted portion. I'm still not entirely sure that I understand said meaning, but from the quoted e-mail and the broader discussion in the paper, it's clear that the authors of the paper view the apparent ¹⁴C age as some form of anomalous background. Hence "ion source crosstalk" and "pseudo-14C ions".

Meanwhile, the current draft of the article is implying that the ¹⁴C measured in diamonds is ¹⁴C that's been there since the diamonds were formed, which in turn implies that either ¹⁴C is defying current understanding of radioactive decay, or that the diamonds were formed ~80 kya (if it's implying something else completely, can you let us know what that is?).

Now, since neither of these latter interpretations are supported by either the paper or the author statement above, it seems to me that the article is misrepresenting the paper by quoting a single, ambiguous sentence. To my POV, the sentence is at best a unnecessary addition which will likely confuse a general reader, and at worst an attempt to imply that either radiocarbon dating is bunk or that the stratigraphy that aged the diamonds is. To this end, I'm commenting out the sentence again. Cheers, --PLUMBAGO 17:05, 28 August 2008 (UTC)

Please show where the measured results from the paper do not support the latter interpretation. Dan Watts (talk) 18:30, 28 August 2008 (UTC)

[Reset indent] OK, for starters, the paper's title is ... [note: all emphasis below is mine]

“ Use of natural diamonds to monitor ¹⁴C AMS instrument backgrounds ”

Which is, as paper titles are generally supposed to be, pretty clear about its subject: instrument issues. Next, the first sentence of the abstract is ...

“ To examine one component of the instrument-based background ... ”

Again - this is pretty clearly to do with the technique, not the samples. Next, from the introduction ...

“ One of these categories is instrument or machine background which involves the registration of what is interpreted by the detector circuitry and/or software as a ¹⁴C-ion produced pulse when, in fact, a non-¹⁴C-ion mimics ¹⁴C or the detector counts ¹⁴C which was not originally present in the sample matrix when it was introduced into the source ”

“ On this basis, we propose that we have eliminated the major sources of mass 14 ion with the exception of that contributed from various components of instrument or machine background signal and perhaps that contributed from the sample holder itself ”

As Jclerman has already pointed out above, the paper then goes off into detail of how and why ¹⁴C detectors report young ages for old samples. At no point does the paper discuss or support the notion that either radiocarbon dating or stratigraphy are flawed enterprises. A simple statement to the effect that the diamonds were not as old as assumed would be expected on this point. Although, were that the case, a whole new paper in a very different journal (Nature, Science) would be more likely. The paper is simply trying to narrow down sources of error in ¹⁴C measurements such that older samples can be more reliably dated. For the WP article to suggest otherwise, as it did with the ambiguous, decontextualised quotation, is misrepresenting the paper and essentially original research. --PLUMBAGO 13:10, 29 August 2008 (UTC)

P.S. I've said "original research" above, but I should just have quoted the relevant portion from the page ...

“ Article statements generally should not rely on unclear or inconsistent passages nor on passing comments ”

My argument, obviously, being that the quoted sentence is unclear given the subject matter of the paper. It simply doesn't represent the rest of the paper's content. Cheers, --PLUMBAGO 16:09, 29 August 2008 (UTC)

Its been disproven!

It's true. A few of us chemists and geologists at Carleton University in Ottawa have disproven carbon dating due to the major increase in Carbon 14 after nuclear atmospheric testing within the past 50 years. This makes it inaccurate and should no longer be used as an excuse to prove global warming exists, which it obviously doesn't. —Preceding unsigned comment added by Pillsberry (talk • contribs) 14:56, 19 September 2008 (UTC)

That's cool. I think i speak for all of the editors here when I say that we look forward to including this exciting material in the article, just as soon as it's been published by a reliable source. SHEFFIELDSTEEL^TALK 19:09, 19 September 2008 (UTC)

To the Carletonians: Thanks very much for alerting us about such breathtaking results. However, since your paragraph has internally and externally inconsistent statements we have alerted Car;etpm about possible deficiencies in their instruction, just in case you are really related to Carleton. Once you've approved the basic courses, you should plunge into the excellent publications about radiocaron dating published by Carleton's faculty. They are all accessible in the website of Carleton University. Jclerman (talk) 22:13, 19 September 2008 (UTC)

Although you doubt my sources, for which you are excused, do you believe that atmospheric nuclear testing does affect the results of carbon dating? It has been shown not only at Carleton(not Car;etpm) but in world wide research that this isotope of carbon was produced. This makes measuring the decay basically useless —Preceding unsigned comment added by Pillsberry (talk • contribs) 01:36, 20 September 2008 (UTC)

Actually it is the exact opposite Pillsberry because the atomically generated C-14 has now given scientists studying this field a new source of C-14 and a carbon spike that can be used for new applications. It's been known for decades now that radiocarbon dating of samples known to be within the range of the Before present age have incorporated atomically generated C-14 into their systems and as such samples of air collected since the 1950's have given scientists a base line used to calibrate the dating of modern samples. This along with samples of a known date has allowed scientists to accurately date fish, also check out this report, as well as Beluga whales. The applications are just now starting to be researched and prompted an article in the journal Science titled "The Mushroom Cloud's Silver Lining". Also, not only would no one understanding how C-14 dating works ever make the assertion that it is "...inaccurate and should no longer be used..." since the C-14 clock only starts when the organism dies and stops integrating new carbon into their body, but as everyone can see from the above articles the new atomically generated C-14 caused by weapons testing is making dating modern organisms not only possible, in some cases, but also more accurate than ever before. RiverBissonnette (talk) 19:12, 18 January 2009 (UTC)

The increase in carbon-14 in the atmosphere due to nuclear weapons testing does not render radiocarbon dating useless because radiocarbon dating is calibrated to cancel out the effects of changes in atmospheric concentration. See Radiocarbon_dating#Calibration.80.235.60.123 (talk) 14:11, 29 October 2008 (UTC)

Issues about instrument qualification and method validation needs to be addressed or mentioned

with some references somehow. —Preceding unsigned comment added by 202.173.190.40 (talk) 00:58, 27 January 2009 (UTC)

Not really sure what you mean. What is instrument qualification? Babakathy (talk) 03:12, 27 January 2009 (UTC)

Before Present

The above article needs some attention from those who know the subject. It particularly need to to better explain the difference between a BP "year" and a calendar "year" (ie that you can not simply equate 10,000 BP to the calendar year 8050 BC by calculating 1950 - 10,000 = 8050). I have added a layman's understanding, but I am sure others could do better. Blueboar (talk) 15:19, 1 June 2009 (UTC)

Radiocarbon dating used to find age of persons born after 1940

The Carbon-14 article quotes this source http://en.wikipedia.org/wiki/Carbon-14#cite_note-11 that details how radiocarbon dating has been used to determine the age of victims of natural disasters. I think there should be a section about this in this article also. —Preceding unsigned comment added by Haakenlid (talk • contribs) 12:14, 21 July 2009 (UTC)

Plaigirism?

I found a website from the U.S. Bureau of Land Management, that has some of the exact same text as on the article...

BLM page

"The radioactive decay of carbon-14 follows an exponential decay. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. Symbolically, this can be expressed as the following differential equation, where N is the quantity and λ is a positive number called the decay constant:"

From the Wikipedia article:

"The radioactive decay of carbon-14 follows an exponential decay. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. Symbolically, this can be expressed as the following differential equation, where N is the quantity and λ is a positive number called the decay constant:"

Perhaps we should do some archive searching to see which site came up with it first?

Samcan (talk) 16:49, 26 September 2009 (UTC)

That section of the article has been in its present form since early February 2006 [9]. My guess FWIW is that the website you found got it from the Wikipedia article. Mikenorton (talk) 19:48, 26 September 2009 (UTC)

NPOV

Tag removed since I added the opposing POV. Both references are now cited in the article and linked to their sources:

• Carbon clock could show the wrong time.
• By studying a stalagmite from a cave in the Bahamas, UA researchers provide a more accurate way for radiocarbon dating to find the ages of ancient artifacts.

Jclerman 20:43, 8 January 2007 (UTC)

NPOV tag readded because of the elimination of the "creation cruft". Specifically I'd like to see the information contained here: http://www.answersingenesis.org/creation/v21/i3/fossilwood.asp included. You must realize that there are a number of intelligent, well-educated people that don't agree with radiocarbon dating because the results don't come out like they should. You can't just ignore and delete information you don't agree with and then pretend that you've got a neutral point of view and nuke the tag. —Preceding unsigned comment added by 200.121.111.113 (talk) 13:07, 9 January 2007

Also there are a number of intelligent, well-educated people that sincerely believe that the Earth is flat, but they fail to provide scientific proof. You provided a reference that erroneously described how stalagmites are formed (by evaporation of CO2) and that claimed that radiocarbon dates were wrong. I provided a reference that, on scientific basis, stated the contrary: in fact that the stalagmite finding will contribute to better and extended calibration of the C14 scale. Thus I felt that removing the NPOV tag was warranted. Jclerman 16:18, 9 January 2007 (UTC)

Tag removed - you will need a more reliable source than that. And, yes I realize that there are a number of intelligent, well-educated people that don't agree with radiocarbon dating because the results don't come out like they would like them to - to fit their preconceived religious views. This article discusses science - not religion. Vsmith 14:21, 9 January 2007 (UTC)

Quoting from http://en.wikipedia.org/wiki/NPOV

Well, in that case we would also have to remove all information stemming from sites of people with a materialistic bias, which is just as religious as Christianity or Creation science. Guess that would leave the article empty after a while. The arguments against radiometric dating are valid no matter what the religious beliefs are of the person making them. --41.19.78.193 (talk) 12:32, 22 March 2011 (UTC)

The neutral point of view is a means of dealing with conflicting views, and is something strongly recommended for use in writing. The policy requires that, where there are or have been conflicting views, these should be presented fairly. None of the views should be given undue weight or asserted as being the truth, and all significant published points of view are to be presented, not just the most popular one. It should also not be asserted that the most popular view or some sort of intermediate view among the different views is the correct one. Readers are left to form their own opinions.—Preceding unsigned comment added by 200.121.111.113, 9 January 2007 (talk)

I don't understand the explanation of carbon dating provided in Wikipdia. Why does the C14 fraction start changing only after an organism has died? The radioactive beta decay of C14 takes place (both in the organism and in the atmosphere) regardless of whether or not the organism is dead, doesn't it? It seems to me that a complete explanation has to consider some kind of production mechanism of C14 in the atmosphere which keeps the fraction in equilibrium in the atmosphere (and therefore in plants through absorption of carbon from the atmosphere).131.151.79.118 (talk) 14:47, 29 August 2008 (UTC)

The first section of the article ('basic physics') goes some way to explaining this. There are "unremitting cosmic ray impacts on nitrogen in the Earth's atmosphere, which create more of the isotope", maintaining the equilibrium. Organisms absorb 14C through respiration, so the levels of 14C remain relatively constant during the organism's life. Once an organism dies there is no process to replenish 14C and it decays. Nev1 (talk) 15:03, 29 August 2008 (UTC)

Don't organisms respire oxygen? 69.9.30.179 (talk) 15:38, 29 August 2008 (UTC)

Sorry, improper use of respiration. I believe I should have said breathing. Nev1 (talk) 15:59, 29 August 2008 (UTC)

Not at all. Plants fix carbon by photosynthesis and animals ingest plants or animals. 69.9.30.179 (talk) 20:26, 29 August 2008 (UTC)

Correct. Animals acquire ¹⁴C as organic material usually derived from plants, and they release it to the atmosphere via respiration (during which they consume oxygen). Plants, however, can fix ¹⁴C to organic material straight from the atmosphere as ¹⁴CO₂. However, the above explanation for what happens to the ¹⁴C fraction after death is otherwise mostly correct. While alive, animals (and plants) constantly turn-over their carbon content, and the ¹⁴C fraction is relatively constant (although it's actual value may differ between the atmosphere, plants and animals because of isotopic fractionation effects). When they die, and their bodies are not consumed by other organisms (the fate of most dead organisms), radioactive decay of ¹⁴C will decrease the fraction of ¹⁴C in the body, such that when it's analysed at a much later date, the ¹⁴C fraction is significantly less than would be found in a living organism. The amount by which it's less can then be used to infer the time that has passed since the organism died. Hope this helps. Cheers, --PLUMBAGO 16:02, 29 August 2008 (UTC)

Excellent explanation. I'd suggest a slight amendment - When plants are alive, for instance trees, they are continuously capturing carbon out of the air, with its current C14/C12 ratio, and from this carbon building woody stems and trunks. So for a tree that lives 100 years, the C14/C12 ratio of the inner trunk will match what the atmosphere had at the start of its life, the outer trunk at the end of it 100 years later, and you see the pattern for intermediate layers. After that carbon is captured, it starts decaying. For the inner trunk, this will occur while the tree is still alive. Only the outermost layer of a tree trunk is "alive". —Preceding unsigned comment added by Friendly person (talk • contribs) 23:34, 22 August 2010 (UTC)