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Request for Comment: Disputed accuracy

I do not understand why the information regarding the fact that there are groups that dispute the accuracy of carbon dating continues to be removed from this article. Please can those involved explain their actions? Many thanks, --Rebroad 00:07, 5 February 2007 (UTC)

Removed:

== Controversy ==
Carbon dating is extremely controversial amongst fundamental religious believers such as creationists. It can be used to prove the existence of items older than the supposed age of the Earth. Creationist scientists have questioned its accuracy although none of their research has yet been subject to satisfactory peer review.
The last sentence isn't exactly true. The arguments made by creationists against radiometric dating methods are from simple physics and chemistry and directed against unprovable assumption made by those that use radiomatric dating methods to claim the age of objects. --41.19.78.193 (talk) 12:44, 22 March 2011 (UTC)

In the Bible, the Hebrew word used for "day" is "yohm", which often means different lengths of time, such as the length of time it takes for a season, which takes a few months - much longer than a 24 hour day. It can be used to describe the period of time it takes for an event to occur, and thus if these "days" took millions or billions of years it would still be accurate to the meaning.

Responses to RfC

  • Quite simply, there is no controversy as such within science and this is an article about the science. It is plainly creationist pseudoscience being pushed by a number of vocal YECers. Of course they object -- It can be used to prove the existence of items older than the supposed age of the Earth. -- as it sorta kills their religious foundation. It is not science and there is no controversy outside the minds of the pov pushers. You are most welcome to add the info (with sources) to the creation (pseudo)science article. Vsmith 01:12, 5 February 2007 (UTC)
See http://www.google.co.uk/search?q=carbon+dating+controversy&sourceid=navclient-ff&ie=UTF-8&rlz=1B3GGGL_enGB209GB209 - 576,000 articles according to Google, all mentioning that there exists controversy. --Rebroad 14:23, 12 February 2007 (UTC)
Firstly, if you put "carbon dating" in quotes, that reduces the number of hits by an order of magnitude (you may be including sites where chemists can get themselves a date). Secondly, try substituting phrases like "apple sauce" and "chicken salad" in for "carbon dating"; note how many hits you get. Thirdly, since when was Google a substitute for peer-reviewed science? The "controversy" exists only in the minds of those people who have a particular "literal" reading of a particular religious text. Beyond them not getting the answer that they want from science, what are the grounds for concluding that there's a "controversy" here? Yes, the method has issues, but all scientific methods are imperfect, and its imperfections are not those touted by creationists. Please give us something useful to work with here. --Plumbago 15:09, 12 February 2007 (UTC)
If what you say is true, that is is an article on only the scientific aspect of Radiocarbon dating, then I suggest it be renamed to "The science of radiocarbon dating", with a new article on radiocarbon dating pointing to it. However, as the article currently stands in size, I do not think a seperate article on the scientific aspects only is warranted. What do you think? --Rebroad 15:22, 5 February 2007 (UTC)
Please take a look at the discussion below. Radiocarbon dating IS a scientific topic, therefore the article should focus on the science and leave the pseudoscience stuff elswhere. Note - the addition of an external link to a baptist missionary propaganda page to the top of the external links section seems strikingly odd - like pov spam to me. Vsmith 15:37, 5 February 2007 (UTC)
  • Calibration issues already are discussed in the article, so the deleted material adds nothing of scientific relevance. There's no need to clutter up the article with allusions to non-science issues such as creationism. Raymond Arritt 02:25, 5 February 2007 (UTC)
  • Agree with Vsmith, Raymond Arritt and Geologyguy: there is no real controversy in the use of 14C. Creationists get upset with it only because it points to an older Earth than their worldview allows. The same could be said for any number of other radioisotopes or proxies used to infer age (tree rings, ice cores, seafloor sediment, etc.). There are, as the article describes, legitimate issues concerning the interpretation of 14C data, but denialism founded on a scientifically-bankrupt ideology isn't one of them. And on a purely pragmatic level, inclusion of these "concerns" here is tantamount to opening the door for similar edits on any of the thousands of articles on scientific topics (half-life anyone?). Creationism hasn't just got problems with 14C; it has problems with science period. --Plumbago 15:42, 5 February 2007 (UTC)
  • If there is no 'controvsery' why is it impossible to state the accuracy of carbon dating? We get dates like 2,300 +/- 30 years where 30 years is the chem lab error in measuring the C14 per volume, but where is the error in assumptions made of the C14 hypothesis? It is assumed 0%, surely someone has done something to try to quantify these errors apart from 'good fits' with objects of known age.--Dacium 02:30, 6 February 2007 (UTC)
The thing is, these errors are impossible to quantify, any number would be spurious, so you don't presume to give one. It is up to the archaeologist to know what to make of the result.
N.B: The German version of the article has a separate section about all the reasons why the laboratory age may be wrong, contamination, reservoir, old wood, etc. I suggest it might be a good idea to group all these here too.Axel Berger 09:36, 6 February 2007 (UTC)
  • Radiocarbon dating is quite accurate--and getting more accurate with new techniques--when it is applied to suitable materials. The big difficulty with carbon dating as compared to other radiometric dating techniques is the high likelyhood of contamination. This much is acknowledged by scientists, who take pains to find clean samples, and a robust discussion of the appropriate use and degree of accuracy can be found in almost any graduate level textbook on the subject. The problem with YECs is that they have generated a false sense of inaccuracy by submitting inappropriate materials for testing in radiometric laboratories. The inaccuracy produced by measuring, say a 10 year old basalt, with C14 methods is somewhat akin to the inaccuracy produced by measuring the temperature of boiling lead with a rectal thermometer; you won't find the tempurature of the lead, you will only find the upper limit of the thermometer. Aelffin 03:16, 6 February 2007 (UTC)
  • I think it should stay out. This is an article about the technique. The fact that it contradicts creationism is fairly tangential . The very WP:POV statement discrediting the technique's critics, if anything, gives undue weight to the critics arguments. --Selket Talk 21:29, 12 February 2007 (UTC)

A sample covered by Noah's flood for a year or so would totally contaminate the sample. Considering everything was under water 4400 years ago, any sample that is analyzed has been contaminated. The dates assume that the samples are not contaminated and that the decay has been constant for the life of the sample, which cannot be proven. --Ryanincabo (talk) 15:33, 27 April 2010 (UTC)(UTC)

Following your logic, a sample contaminated by newer material, ie by a recent flood, would appear to be younger than it actually is because it would receive a fresh infusion of carbon 14. As a result, your argument isn't logical. Your argument also pre-supposes a global flood only a few thousand years ago. There is no evidence that a global flood happened so recently or even could happen at all. All you're really doing is making Christians sound morons. Rklawton (talk) 15:45, 27 April 2010 (UTC)

In order to address the "controversy" could someone include a discussion around why we are confident that the ratio of Carbon 12 to Carbon 14 in the atmosphere has remained a constant. I understand the issue is that the current ratio (100 Trillion to 1) when extrapolated back has remained fairly constant according to the "old age" camp and was much different according to the "young age" camp. If the focus was on the reasons for the accepted extrapolated ratio surely the "controversy" could be managed without turning the article into a discussion of religion etc — Preceding unsigned comment added by 86.26.184.88 (talk) 21:03, 15 June 2011 (UTC)


Calibration

In a section titled "Calibration" the last paragraph is:

As a consequence, the radiocarbon method shows limitations on dating of materials that are younger than the industrial era. Due to these fluctuations, greater carbon-14 content cannot be taken to mean a lesser age. It is expected that in the future the radiocarbon method will become less effective. A calibration curve must sometimes be combined with contextual analysis, because there is not always a direct relationship between age and carbon-14 content.[13]

I am not sure if ref 13 is supposed to support the whole paragraph or just the last sentence, but it does neither. The reference ("Coral corrects carbon dating problems.") is a 1990 Science News article describing how using ancient coral reefs, radiocarbon dating accuracy is improved. The article has no mention of industrial era or predictions for decreased assay accuracy in the future. The article concludes that, as common sense would dictate, a refined calibration curve for a particular assay improves the assay accuracy.Desoto10 (talk) 04:45, 25 February 2011 (UTC)

I agree, you're absolutely right. Axel Berger (talk) 02:56, 6 March 2011 (UTC)
Where did that paragraph go? Reference 13 seems to have disappeared. It is generally true that for any given sample eventually "the radiocarbon method will become less effective" if for no other reason than the usual 30,000 - 60,000 year fuzzy boundary of the technique's precision. But sufficient unto the era is the evil thereof. For industrial revolution samples, we can worry about that in 30,000 years time.
Generally there are problems with accounting for industrial effects, partly because of the unequal distribution of such effects around the globe. I don't know of a particularly good review article covering the issue, but you do come across it the literature. Also, for technical reasons including counting error, carbon dating isn't good at dating samples really close to the present (like a few decades). And the issue is confused by B.P. referring to the 1950 epoch. Carbon dating is beginning to be useful at around 200 radiocarbon years, which allows for use in industrial history. For earlier dates the problems are not insurmountable but do rely heavily on special measures like local sampling to improve calibration curves.
More serious is the potential for increased "wiggle" size resulting from rapid changes in industrial usage. The "wiggles" in question are short-timescale events (about a human generation long) where the radiocarbon year:real year curve actually reverses slope.
These "ambiguous regions" in the calibration curve mean problems of date matching are even more pronounced than those associated with the longer term so-called plateaux. Think about it - a single radiocarbon date in a known "wiggle" would have three possible corresponding true dates - the "mapping" is not a "function".
The problem's even worse than this. Any such single radiocarbon date is the centre of a bell-shaped counting distribution curve. That is, the "real" date of the sample most likely falls within an interval surrounding the measured date. Mapping that counting error through the wiggle introduces bizarre changes to the bell-shaped curve - a problem known to specialists as "calibration stochastic distortion" (CSD).
Even for a simple plateau, where the curve doesn't actually reverse slope, the CSD effect is easily shown to be that a single radiocarbon date has a bimodal distribution of 'true' years B.P. - like a Bactrian camel's double hump. I actually wrote a paper discussing this for "Radiocarbon" (the scientific journal) with McFadgen and Knox, gosh, nearly twenty years ago.
In fact, if you want a reference to "A calibration curve must sometimes be combined with contextual analysis, because there is not always a direct relationship between age and carbon-14 content", you could do worse than look through back issues of "Radiocarbon". I'm surprised reference 13, whatever it was, turned out to be so defective. The issue is so widely known it's more or less presumed as background.
Fortunately, the further back in time, the less important such wiggles become in comparison with the long term trend. Eventually the stochastic distortion from wiggles is insignificant compared to the counting error. But for the industrial era, it's quite significant. --Sdoradus (talk) 12:06, 29 May 2011 (UTC)

the gospel of carbon 14

I have a problem with this calculation. It seems like this method of dating postulate two truths.

  • Carbon 14 generating cosmic rays has been at about the same intensity, as currently measured, in the far past.
  • All living matter has some given fraction of Carbon 14 out of all the carbon in it's body. this fraction is proportional to the proliferation of C14 in the atmosphere. this is derived from geo-specific and current measurements.

These two claims are the result of an extrapolation, that although they might be used as a gauging measure, they might also, sometimes be ,way off the true age of the sample.--Namaste@? 02:44, 8 July 2011 (UTC)

Do you have a suggestion for article improvement? The talk page is for article improvement only. Thanks.Farsight001 (talk) 04:00, 8 July 2011 (UTC)
He has no other option left. The guy did try to improve the article along the lines of his comment above and the revision was swiftly undone. Correctly in my view, but that leaves him with only the discussion page, which is or should be for discussion of proposed revisions. --Sdoradus (talk) 02:11, 9 July 2011 (UTC)
What was needed back on 9 June when the same content was added to the article was reliable sources to support the addition. As it was unsourced, it was removed. Simply posting the same content here with no references or context suggestion for the article is lacking. Provide a valid source and some context for discussion and we'll likely discuss - otherwise it will be ignored here. Vsmith (talk) 03:22, 9 July 2011 (UTC)
I assumed it will be swiftly deleted, and so it was. Wikipedia is much less open than it thinks it self to be :)
Main point being, that this scientific hypothesis, acclaimed as it is, NEEDS a criticism section.
And the criticism section should not be nullified. My two questions remain, how do we KNOW that atmospheric C14 cycle and density was about the same as it is now, millions of years ago? --Namaste@? 21:40, 25 September 2011 (UTC)
First of all, it actually doesn't need a criticism section. Criticism sections are discouraged. Second, carbon 14 dating is in no way a hypothesis. Calling it that makes me wonder if you know what it actually is. As for how we know - extensive research and testing. Might I guess that your sources claim that such things are an assumption? Well they are lying. Farsight001 (talk) 21:54, 25 September 2011 (UTC)
Agree with Farsight001. The questions Namast@ raises are answered in the section Calibration already. Btw, carbon dating is not used for "millions of years", but at most for a few tens of thousands of years. Zerotalk 13:43, 26 September 2011 (UTC)
I am disappointed by these statements. They promote non-discussion. which is, of course, the issue, and why i called this sections "the gospel.."
First one, saying that this article does not need a criticism section, just because it doesn't...is not even a stupid argument. it is a non-argument.
Secondly, My questions remain unanswered. No need to assume I have contrasting information or hidden agendas, I am simply noticing that the methods used to arrive at this info are very arbitrarily "calibrated", and are based on retroactive assumptions.
If the carbon14 cycle, changes even 0.01% per 1000 years (or by 100% each nuclear test..), than all of our "assumptions" of linear-change or no-change are wrong. Fact is, we do not know. and I have yet to find ANY falsifiable claim or method saying otherwise. --Namaste@? 17:13, 9 October 2011 (UTC)
Which is why scientists have already tested those things. They are not assumptions. Fact is, we DO know. Now, again, do you have suggestions for article improvement? This is not a forum for the discussion of the merits of radiocarbon dating, but for the improvement of the article. Farsight001 (talk) 20:35, 9 October 2011 (UTC)
To Namaste@, actually the change is more than 0.01% per 1000 years. But you misunderstand how the dating works. These days, ages are not determined by extrapolating backwards from the present conditions. What actually happens is that the measurements of a sample are compared against a large database of samples whose age has been determined by other methods. Many of the samples in the database have very accurate dates, such as by counting tree rings, and the database is being refined and extended all the time. The database is used to periodically issue calibration curves (implemented as computer programs) that translate raw measurements into a range of plausible dates. Nevertheless, people who do radiocarbon dating always publish the raw measurements as well as the dates, so that the dates can be reassessed in the future when the database is improved. Zerotalk 01:07, 10 October 2011 (UTC)
So...can this section of the discussion be deleted yet? Either it was a misunderstanding, an attempt to undermine the credibility of the method, or an inadvertent argument for adding a criticism section based on the prevalence of misinformation and misunderstanding in popular culture. If it's to be taken at all seriously as the last, perhaps someone could summarize where people frequently get things wrong...but I have no idea what kind of sources could be cited, so perhaps it's really not to be taken seriously, and this section should be deleted... Alousybum —Preceding undated comment added 06:14, 21 February 2012 (UTC).

DISPUTED ACCURACY OF A STATEMENT

The Wiki article says, "He [Libby] first demonstrated the accuracy of radiocarbon dating by accurately estimating the age of wood from an ancient Egyptian royal barge for which the age was known from historical documents."

But according to source cited (source #2), it states the following:

"The next sample was furnished by John Wilson, of the Oriental Institute at the University of Chicago, and was a piece of wood from a mummiform coffin from Egypt, dated on stylistic grounds in the Ptolemaic period 332–30 B.C."

My contention?

The Wiki author's statement is misleading; it makes one think that there was some kind of manuscript evidence stating the date of an ancient Egyptian royal barge, when the source makes it abundantly clear that this barge's age was known through the use of stylistic dating. — Preceding unsigned comment added by 74.34.85.10 (talk) 18:27, 18 August 2011 (UTC)

Hi, welcome to Wikipedia. Please remember to sign your posts and please refrain from using all caps...even when you feel that your post is very, very important (we all feel that way sometimes). I don't think the statement you referenced was deliberately misleading, but it could use some refinement as all articles are works in progress. When you uncover a point like that, please be bold and make the change yourself, then follow up on your changes regularly to see if they have been reverted. If no one objects then you may assume your change was acceptable as silence implies consensus; if you find it reverted, then you should take it to the talk page for constructive discussion. 96.252.169.227 (talk) 04:21, 28 August 2011 (UTC)
Given Farsight001's unwillingness to either 1. rename the article to "the science of carbon dating" or 2. allow a criticism section, I don't think it's that unreasonable to call it deliberate72.152.25.12 (talk) 15:39, 16 November 2011 (UTC)

Anon has a point. I guess "royal barge" is from the museum site which is linked but now defunct. The linked paper of Libby et al was not his first on the subject, there is an earlier one (ref 10 in the linked paper, which is missing from that copy of it). The earlier paper refers to wood from two Egyptian tombs but there is no mention of barges and it doesn't say how the true ages were determined. I'll change the text shortly on the basis of Libby's two papers. Very likely there is more information about it in some reliably sources somewhere... Zerotalk 00:53, 10 October 2011 (UTC)

Nothing happened for a while, so I've removed from historical documents - the dates of the person in the tomb might well be known, but it seems unlikely there are any "documents" as such referring to a barge. Johnbod (talk) 15:48, 16 November 2011 (UTC)
Actually now I look at the linked 1949 paper, it says lower down: "The fifth sample was a piece of deck board from the funerary boat of the Egyptian Sesostris III, which is displayed in the Chicago Natural History Museum. The wood probably is cedar of Lebanon. The sample was kindly furnished to us by the museum through the good offices of C. C. Gregg and Alex Spoehr. John Wilson dated the material as 1843 ±50 B.C." But this was just one of a series of samples. I'll amend. Johnbod (talk) 15:52, 16 November 2011 (UTC)

British English?

I don't understand why this article uses British English. Radiocarbon dating was invented in the United States, and the -ize construction is used more than the British -ise in the article. I think we should change it. --Serpinium (talk) 15:46, 31 August 2015 (UTC)

I marked as using British English because I saw some British English when I began working on it. My own English is a mixture of American and British, which is probably why there are some "-ize" endings. I think it should be left as British English; Libby is the key figure, of course, but I don't think that's enough to assert that the article ought to be in BrEng. Mike Christie (talk - contribs - library) 16:36, 31 August 2015 (UTC)
The -ize ending is commonly used in British English. See the the Wikipedia page American and British English spelling differences#Greek-derived spellings and the Oxford Dictionaries blog here. Aa77zz (talk) 17:07, 31 August 2015 (UTC)
Huh. Thank you for your reply, Aa77zz, I was not aware of that. According to the WP article, scientific publications especially prefer -ize. I've finished reading the article now, and I've compiled a list of all the errors I could find, so I'm ready to go for whichever style we go with. What do you think, Mike Christie (or anyone else reading)? It would be helpful to find some kind of precedent for this on Wikipedia. --Serpinium (talk) 17:50, 31 August 2015 (UTC)
By errors, do you mean deviations from British English? Or deviations from preferred usage in scientific publications? I've no objection to -ize (thanks, AA77zz, for the links; that explains why I use -ize, so perhaps my English has not become as Americanized as I thought it had) but don't feel strongly either way. I do think the article should stay in BrEng absent a convincing reason to change. Mike Christie (talk - contribs - library) 18:14, 31 August 2015 (UTC)
OK, I've gone and made my edit with the -ize intact. Thanks, you guys. --Serpinium (talk) 19:52, 31 August 2015 (UTC)
British English uses both - see Oxford spelling - but it should be consistent. Johnbod (talk) 02:09, 1 September 2015 (UTC)
It's not a really strong national tie so the rule to follow should be consistency. Kortoso (talk) 20:39, 7 July 2016 (UTC)

Cal?

It's not clear thru this article whether "cal" refers to "calendar" or "calibrated". The difference can be significant. Kortoso (talk) 20:41, 7 July 2016 (UTC)

Well, the "Reporting dates" section is the first place "cal" is used, and there it's defined as "calibrated", not "calendar". I don't think there are any uses of "cal" next to a date before that point in the article, are there? Mike Christie (talk - contribs - library) 20:46, 7 July 2016 (UTC)

Recent changes to history section

KLindblom, I have a couple of suggestions and questions about your changes to the history section.

  • I'd prefer not to start the section with the statement that Libby came up with the idea in 1946. I think you're referring to his 1946 paper, which is mentioned later in that section. I would like to keep the section chronological, and avoid the implication that he didn't have the idea till 1946, so I'd like to cut that first sentence.
Chronological is a good idea. I've removed the biographical info on Libby that started the section. Since Libby didn't become interested in 14C until after Korff's research, it makes sense to introduce him later in the section.
  • I see you removed the reference to Danforth's co-authorship of Korff's paper? Korff was the principal author; does that mean we don't need to mention Danforth? I don't have a source that specifically says that the ideas in the paper were Korff's, so I mentioned both.
In several sources (including his 1960 Nobel Prize lecture), Libby cites Korff alone as providing the inspiration for radiocarbon dating. Therefore I think it's adequate to list only Korff.
  • I'm not sure the National Historic Chemical Landmarks program should be mentioned in that section; it's not really part of the history, just a recognition of the history. How about making that a category of some kind instead?
Good suggestion. I've moved the award to the Impacts section of the article. If you disagree, feel free to remove it.

Let me know what you think. -- Mike Christie (talk - contribs - library) 03:11, 10 October 2016 (UTC)

Hi Mike Christie. I've inserted my responses along with your bullets (above). Thank you.
I tweaked your changes a little more; let me know if that looks OK. I think the Landmark award might be better as a category, but I don't feel strongly about it so let's see if others comment. Mike Christie (talk - contribs - library) 10:55, 10 October 2016 (UTC)

Council for British Archaeology

A note in British Archaeology, the magazine of the Council for British Archaeology, states

Radiocarbon dates: Unless otherwise noted, 14
C dates in British Archaeology are calibrated at 95% confidence (cal AD or cal BC, expressed as AD or BC), and rounded out after Mook (1986). See wikipedia.org/wiki/Radiocarbon_dating

Congratulations to Mike for his work in producing such an authoritative article. Dudley Miles (talk) 19:49, 30 October 2016 (UTC)

Wow! That's very cool. Thanks for letting me know! Mike Christie (talk - contribs - library) 20:17, 30 October 2016 (UTC)

The Ineffectiveness of Carbon-Dating

I don't deny that Carbon-dating could be useful, but I feel that scientists might have made a mistake. Where did they get that half-life number, for instance, and are they sure that the radio-activeness rotted evenly? With (I hope) all due respect, I feel they should rethink their theory or mention the fact that they used carbon-dating whenever they did. With both respect and frustration, Myrrhfrankincensegold (talk) —Preceding undated comment added 23:23, 21 December 2016 (UTC)

If you have a WP:reliable source re: scientists might have made a mistake, then let's have it. Sorry 'bout your frustration :) Vsmith (talk) 18:17, 23 December 2016 (UTC)

Nitrogen

"The radiocarbon dating method is based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen."

This could definitely use a reference or a sentence of explanation as it seems that this is saying that cosmic rays transmute nitrogen into carbon, which is rather amazing. — Preceding unsigned comment added by 75.173.77.201 (talk • contribs)

It's cited in the body of the article; the lead section of articles usually doesn't have citations, since the information is always in the body of the article too, and should be cited there. Mike Christie (talk - contribs - library) 20:42, 2 September 2017 (UTC)

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Background - History - Korff

This section contained the phrase "... it was this paper that gave Libby the idea..." but the previous text in the wiki article didn't mention a particular publication. I've dug a little further to identify which paper was meant and found there were several papers by Korff but none quite stated that the interaction of slow neutrons with N14 in the atmosphere "was the main pathway". I've tweaked the text. Also Korff wasn't at NY Uni at the time.

Google preview allows me to see Taylor & Bar-Yosef 2014 on page 269 - and also Note 38 on page 325

  • Korff and Danforth 1939 is here It discusses the detection of neutrons in the atmosphere and doesn't mention carbon. According to Taylor & Bar-Yosef it was this article that Libby referred to in an interview.
  • Bethe et al 1940 is here. It mentions the cross-section of N14 to thermal neutrons in producing C14 and cites earlier work on this reaction.
  • Korff 1940 is here. It includes the text quoted by Taylor & Bar-Yosef: "Since each [neutron] will most probably be eventually captured by nitrogen, nitrogen will be disintegrated, forming long-lived C14 at a rate of q=10-6 atoms per cc per second in the upper atmosphere."

- Aa77zz (talk) 15:16, 6 January 2017 (UTC)

@AA77zz:: would you mind taking a look at the discussion about slow/thermal neutrons here, and let me know what you think? I can't access Korff 1940, but I think the right answer would be to use whatever characterization Korff used, or drop the temperature adjective completely, rather than adjust Korff's language to match the modern usage of "thermal" and "slow". Mike Christie (talk - contribs - library) 02:20, 28 November 2017 (UTC)

Background - Dating considerations - Isotopic fractionation

The page currently states, 'The 13C/12C ratio is used instead of 14C/12C because the former is much easier to measure, and the latter can be easily derived.' I am not a subject expert, but question whether this is incorrect. Should it read, 'The 14C/12C ratio is used instead of 13C/12C because the former is much easier to measure, and the latter can be easily derived.'? — Preceding unsigned comment added by AHDGraham (talk • contribs) 07:15, 7 October 2017 (UTC)

It's correct as written. The 13C/12C ratio is easier to measure because 13C is much more abundant than 14C, so a mass spectrometer can easily find the relative proportions of 12C and 13C. As a result δ13C is used in the fractionation calculations. Mike Christie (talk - contribs - library) 08:56, 7 October 2017 (UTC)
Yes, but that's not the reasoon, is it? 14C is changed by two processes, ageing and fractionation, and 13C by only one. To isolate the aging, i.e. to measure the age, you need to control for any fractionation and you can do that by looking at 13C and then applying the appropriate correction. Axel Berger (talk) 22:37, 23 December 2017 (UTC)

Incorrect English dialect

Why is this written in British English when "the method was developed in the late 1940s by Willard Libby," an American? This should obviously be written in American English. 95.49.133.63 (talk) 15:54, 21 November 2018 (UTC)

Take a look at WP:ENGVAR, which discusses the use of different english varieties, to quote "When an English variety's consistent usage has been established in an article, maintain it in the absence of consensus to the contrary. With few exceptions (e.g., when a topic has strong national ties or a term/spelling carries less ambiguity), there is no valid reason for such a change." I would contest the idea that radiocarbon dating has a "strong" national tie to America other than in its initial development. Mikenorton (talk) 23:20, 21 November 2018 (UTC)

54kyo stalagmite

https://gizmodo.com/two-stalagmites-found-in-chinese-cave-are-a-holy-grail-1831074289

The above is interesting and the info from it should probably go into the article. 173.228.123.166 (talk) 12:18, 15 December 2018 (UTC)

This is based on the article in Science by Cheng et al (2018): http://science.sciencemag.org/content/362/6420/1293 - Aa77zz (talk) 13:38, 15 December 2018 (UTC)

I've just read the article, and was going to add something like this:

Since INTCAL13 was published, analysis of stalagmites from Hulu Cave in China has produced a detailed record of atmospheric 14C back to 54,000 years before present.

That's a bit bare-bones and context-free, though. What I'd really like to say is something like "this data will be incorporated into the next INTCAL curve" and will help improve the accuracy of 14C dating", but I can't do that with just this article. Any thoughts on how to integrate this? Mike Christie (talk - contribs - library) 11:49, 16 December 2018 (UTC)

WikiJSci version

A version of this article has been published in the WikiJournal of Science. I am about to go through the article and change some of the text to incorporate modifications made to that article during peer review. If anyone feels the changes are not an improvement, please comment here. Mike Christie (talk - contribs - library) 20:16, 9 June 2018 (UTC)

Here is the diff of the completed changes. The peer review is visible here. Mike Christie (talk - contribs - library) 21:03, 9 June 2018 (UTC)
And in case anyone feels it's a conflict of interest for me to cite myself, I'll point it out here. The WSJ article is cited as a source for a short phrase. Mike Christie (talk - contribs - library) 01:55, 10 June 2018 (UTC)
British Archaeology, the journal of the Council for British Archaeology, has a box in each issue recommending the Wikipedia article for information about radiocarbon dating. Last month, I wrote to the journal informing them of the WJS article and they have published my letter in the November/December 2019 issue and changed to recommending the WJS version. Dudley Miles (talk) 14:34, 10 October 2019 (UTC)

New technique

Mike Christie. You may be interested in a new method of dating pottery by radiocarbon dating of milk fat residues reported in the latest edition of Current Archaeology. It is described as a "potentially revolutionary advancement" and the report is based on an article in Nature at [1]. Dudley Miles (talk) 19:15, 12 May 2020 (UTC)

Aa77zz mentioned it to me on my talk page, and I read the article and asked my archaeologist friend about it. His take was that it was certainly an advance, but perhaps not revolutionary -- he gave me some examples of papers about dating pots from organic matter other than food residues -- e.g. organic temper in a pot can be radiocarbon dated. He did suggest that it would be a good component of a section on radiocarbon dating of ceramics, covering dating temper as well. I don't think I'm up for adding that to this article, not at the moment at least -- it would require quite a bit of specialist reading and might even be a separate article. Mike Christie (talk - contribs - library) 01:38, 13 May 2020 (UTC)
My take on it is, that its true value is not so much much in dating the ceramics but the residues. It's only quite recently that milking has been shown to have occurred much earlier than originally assumed from just those residues extracted from ceramics. So it's gratifying to have it now confirmed, that these residues are in fact as old as the ceramics themselves and no later intrusuion. Axel Berger (talk) 12:59, 17 May 2020 (UTC)

Updates needed

To editor Mike Christie: This article is stuck at IntCal13 and could use an update to the present. It's a bit peripheral to my expertise, so this is a friendly nudge in your direction. Zerotalk 06:16, 9 September 2020 (UTC)

Thanks; you're the second person to remind me! I have the articles on IntCal20 from Radiocarbon and just need to find time to read them and make the changes. I have a couple of other reviewing obligations on-wiki and when those are done I'll do this, if nobody else has done it. Mike Christie (talk - contribs - library) 10:26, 9 September 2020 (UTC)
Now done, at least at a basic level; I've also updated the graph. More could be added, e.g there's a discussion in the IntCal20 article about a significant change in the statistical approach from the previous curves, but I think that's probably too technical for this article. It could be added to radiocarbon calibration. Mike Christie (talk - contribs - library) 16:59, 3 October 2020 (UTC)

Apparent Age

The term "apparent age" / "apparent date" is not introduced before its first use in the article. I kinda hope it will be clearly defined somewhere, but I am not an expert on the topic. Maybe this citation would help? "the 14
C relative to the time of death" (or when the primary activity ends).

  • Mangerud, Jan (1972-06-01). "Radiocarbon dating of marine shells, including a discussion of apparent age of Recent shells from Norway" (PDF). Boreas. 1. Oslo: 145. Retrieved 2020-11-14.
    — Preceding unsigned comment added by 173.75.41.7 (talk • contribs)
I don't believe any of the uses in this article are technical in any way; they have the usual English meaning of "this is what it appears to be", with the usual implication that that's incorrect. The first usage is Dating an object from the early 20th century hence gives an apparent date older than the true date, for example (the preceding sentence in the article explains why this is). Can you say what would make this clearer to a reader? Mike Christie (talk - contribs - library) 12:30, 16 November 2020 (UTC)
Thanks for the reply! I am a total layman here and I can only speak for my own experiences. I recall getting confused between the term "radiocarbon age" and "apparent age" when I was going through that part of the article but wasn't sure if they are essentially the same thing. My guess so far is that radiocarbon age is apparent age but expressed in radiocarbon years? The rest of this article is very, very well written by the way :) 173.75.41.7 (talk) 17:22, 16 November 2020 (UTC)
Thank you! Flattery will get you a long way. No, that's not the intended meaning. Here are the relevant sentences: Coal and oil began to be burned in large quantities during the 19th century. Both are sufficiently old that they contain little or no detectable 14C and, as a result, the CO2 released substantially diluted the atmospheric 14C/12 C ratio. Dating an object from the early 20th century hence gives an apparent date older than the true date. What this means is that if you didn't know about effect of the coal and oil, and ran a radiocarbon date on a bone from 1940, it would give you a date much older than 1940 because the carbon released by burning coal and oil had changed the 14C in the atmosphere by 1940. So someone who didn't take this into account would come up with a date of, say, 1890 (I don't know what the actual error would be). That's the apparent date; the date it appears to be if you don't take the fossil fuel effect into account. The usage later in the article is similar -- if you use radiocarbon dating without understanding e.g. the marine offset, you're going to get radiocarbon dates that are wrong -- they are apparently date X, but if you apply the right correction you get the correct answer, Y. Is that clearer? Mike Christie (talk - contribs - library) 17:35, 16 November 2020 (UTC)

Oops, didn't mean to flatter or something. Thanks for the explanation! In the article, it says The calculations involve several steps and include an intermediate value called the "radiocarbon age"... an age quoted in radiocarbon years means that no calibration curve has been used. So using the same example in your explanation above, a carbon dating result is calculated like this:

Get some bone sample -> remove contaminants -> do a calculation based on just 12C/14C ratio and nothing else -> get the apparent age (1890) -> factor in the considerations as listed in the #Dating_considerations section -> get the radiocarbon age (say, "1950 radiocarbon year") -> use caliberation curve like IntCal to account for atmospheric variation -> final result (1940 calendar year)?

173.75.41.7 (talk) 20:04, 17 November 2020 (UTC)

That's the basic idea, but the details are complicated. Generally, there are two steps: determine the radiocarbon age, then apply a calibration curve to determine the calibrated radiocarbon age. Some factors are included in the radiocarbon age and some in the curve -- see note 6 in the article for the details. If you fail to include any one of the relevant factors you will get a wrong answer, but the place you should have included it might be before or after the determination of the radiocarbon age. For example, if you're measuring something from a marine environment, you should use the marine calibration curve. If you don't, your radiocarbon age won't be affected, because determining the radiocarbon age happens before using a curve, so you'll get the right radiocarbon age but the wrong calibrated age. For another example, suppose you don't make a correction for fractionation. Then you'll get the wrong radiocarbon age, because that calculation is supposed to happen in determining the radiocarbon age. You'll also get the wrong calibrated age, of course, because you'll be applying the calibration curve to the wrong radiocarbon age. So where in your flowchart the error lies depends on what the omission is. (And re "flattery": I just meant thank you for complimenting my writing!) Mike Christie (talk - contribs - library) 12:11, 18 November 2020 (UTC)
Those explains my confusion between “radiocarbon age” vs “apparent age”. Thanks! 173.75.41.7 (talk) 05:29, 22 November 2020 (UTC)

So, is there a need to change the article? Or a way to improve it slightly? --Hob Gadling (talk) 07:12, 22 November 2020 (UTC)

"Confidence" level with OxCal

Under "Calibration", the sentence "For example, 'cal 1220–1281 AD (1σ)' means a calibrated date for which the true date lies between 1220 AD and 1281 AD, with the confidence level given as 1σ, or one standard deviation." - looks very convincing, interpreting the two dates as expressing ±1σ. In contrast, calibrating the age of Ötzi (the iceman) with given 4550 ±19 (= 1σ) BP, OxCal yields for all three confidence levels (68.3; 95.4; 99.7) naturally the same mean μ, however and surprisingly, also the same sigma =89, in spite of naturally different overall dates. For me, the OxCal output is logically contradicting the cited sentence. Any idea?HJHolm (talk) 14:28, 15 June 2021 (UTC)

Yes, there's a small error here. The confidence interval of a calibrated date isn't measured in standard deviations, because they're not normally distributed. What's being expressed is a Bayesian credible interval, usually the HPDI. This whole passage is also lacking a citation. – Joe (talk) 15:24, 15 June 2021 (UTC)

CALIB

As just tested, CALIB confuses the input, taking the "BP" input as ID, and the sigma as BP-age.2A02:8108:9640:AC3:70A7:CB14:FF18:1B02 (talk) 08:07, 3 July 2021 (UTC)

The online version at http://calib.org/calib/calib.html does not have that problem. Zerotalk 09:01, 3 July 2021 (UTC)

Radiocarbon plateau

The term redirects here (at the Calibration section) but the article doesn't even define what a plateau is, not to mention any kind of discussion, and neither does Radiocarbon calibration nor Wiggle matching. It took me a search at the archives of the talk page to find one (by Peter.steier, who is sadly not active for years):

Changes in ocean circulation can release large amounts of "old" marine CO2 into the atmosphere. This old CO2 will be incorparated by living organisms, which will reveal an older radiocarbon age than they "should". They might even have a lower C-14 concentration while they still live than their ancestors a few decades or centuries ago (and have already lost some of their initial C-14 by decay). These are the "wiggles", actually reverting the true and the apparent age.
A "plateau" appears if, over a certain time interval, the change in the atmosphere (due to production changs, reservoir exchange, etc.) BY CHANCE matches the decay-driven change in already dead organisms. All samples from this time interval will finally reveal the same radiocarbon content. If all samples yield the same measurement result independent of their age, dating is impossible (i.e. the uncertainty is the length of the plateau, 800 years for the Hallstadt, independent of the precision of the C-14 measurement). Naturally, perfect plateaus never exist, but the Hallstadt and the Younger Dryas are relatively flat.
— User:Peter.steier
— /Archive 5#Hallstatt plateau 16:22, 13 February 2011 (UTC)

Could anyone please find some sources and incorporate that into the article body? Ain92 (talk) 16:59, 8 August 2022 (UTC)

I agree that we need an explanation. Is Radiocarbon plateau worth a separate article? Dudley Miles (talk) 17:29, 8 August 2022 (UTC)
Any views on this Mike? Dudley Miles (talk) 13:41, 11 August 2022 (UTC)
I think this might be better in radiocarbon calibration than here. The "Intercept" section in that article already shows a plateau in the variations graph, so perhaps just a bit of additional text around there would suffice. I would have to look through my references to see if there's any discussion that I could use to source something, and I don't know when I'd get to that. If there are enough well-defined plateaus or otherwise troublesome areas in the INTCAL curves, a list could be made into a section in that article; I definitely don't have sources for that. Mike Christie (talk - contribs - library) 14:02, 11 August 2022 (UTC)
I think we need an explanation of the term. Anything beyond that would be useful, but would depend on someone having the sources and inclination. Dudley Miles (talk) 14:10, 11 August 2022 (UTC)
I'm fine with that if we can source it, but I just had a look in some references and it doesn't show up in the index, and a Google Books search finds only uses of the term, and no definitions. I think that's because it's not a term of art; it's used for its ordinary dictionary meaning. The term is only used once in this article, in "Wiggle-matching can be used in places where there is a plateau on the calibration curve, and hence can provide a much more accurate date than the intercept or probability methods are able to produce". I would guess that when I wrote that I thought the meaning was obvious, given that the mechanism of intercepts had just been discussed. In the meantime perhaps radiocarbon plateau should redirect to radiocarbon calibration#Intercept? Mike Christie (talk - contribs - library) 14:33, 11 August 2022 (UTC)
How about The Boon and Bane of Radiocarbon Dating, By: Guilderson, Tom P.; Reimer, Paula J.; Brown, Tom A.. In: Science. 307(5708):362-364, 2005? Dudley Miles (talk) 14:55, 11 August 2022 (UTC)
That should do it. I'm about to go into a meeting but if you don't make the edit I'll try to get to it later today or this weekend. Mike Christie (talk - contribs - library) 15:00, 11 August 2022 (UTC)
I have had a go. Of course change anything which is not right. Dudley Miles (talk) 15:48, 11 August 2022 (UTC)
That looks good to me. Mike Christie (talk - contribs - library) 17:07, 11 August 2022 (UTC)

Footnote 12 now reads: because its gradual decay is cancelled out by a gradual temporary increase in the amount of 14C in the atmosphere. – this is wrong - or at least very confusing. The plateau arises when the 14C/12C ratio of the atmosphere decreases at the same rate as the reduction in 14C/12C due to radioactive decay. To quote the cited article "For the duration of such a plateau, the 14C/12C ratio fell at a rate equal to that of radiocarbon decay." - Aa77zz (talk) 19:52, 11 August 2022 (UTC)

So what you are saying is that it is not that amount of 14C in the sample remains the same but that you cannot tell whether the lower level is due to greater age or a decline in the amount of 14C in the atmosphere? That makes sense to me but I will leave it to Mike to say whether it is correct. Dudley Miles (talk) 20:16, 11 August 2022 (UTC)
  • That's exactly what Peter Steier wrote six years ago, quite counterintuitive but makes sense. As a side note, I'm pleasantly surprised by how many users picked my request up! ☺️ Ain92 (talk) 20:34, 11 August 2022 (UTC)
  • Is there only one mechanism for plateaus or might both mechanisms apply at different times? Dudley Miles (talk)
    • On a second thought, I guess that the ratio of 14C/12C which we can later measure may decrease in the environment at the same speed as the natural decay either because new 14C is generated in amounts less than usual, because old 12C is introduced into the environment from some natural reservoir, or for both reasons in some combination? Ain92 (talk) 11:39, 12 August 2022 (UTC)
      Yes, in theory. A reduction in cosmic ray flux would cause less 14C to be created. The second mechanism, an increase in 12C in the environment, could theoretically happen from e.g. a volcanic source, but I'm doubtful about whether that could happen in sufficient quantities and steadily enough to create a plateau, rather than wiggles in the curve. Mike Christie (talk - contribs - library) 12:06, 12 August 2022 (UTC)
(ec) Yes, I'm afraid I read the footnote too quickly. I've changed it to "because its gradual decay is cancelled out by a temporary matching decrease in the amount of 14
C ": is more needed? (post ec) I'm not sure what you mean by different mechanisms -- the points on the calibration curve are calculated directly from the 14C/12C ratio, taken from a sample of known age; there are no other variables. If that ratio had never changed, the line would be straight; the only thing that can cause it to vary (and hence could cause plateaus) is a change in that ratio. Mike Christie (talk - contribs - library) 20:43, 11 August 2022 (UTC)
  • I cannot make sense of your new version. So far as I can see it is not that there is a matching decrease, but that you cannot tell whether 14C level in a sample is an older one when the 14C/12C ratio in the atmosphere was higher or a newer one when the ratio was lower. This is the situation when 14C is declining. What I meant by a different mechanism is the situation when 14C is increasing. Then the 14C level in samples might stay the same for a period because the decline due to decay with age is matched by the increasing 14C level. BTW should we always be referring to ratios rather than levels? Dudley Miles (talk) 21:11, 11 August 2022 (UTC)
    Ratio makes more sense because the equations used all work from the 14C/12C ratio, not from absolute value; the amount of 14C in a plant while it's alive depends on the ratio. Re your question: if the 14C/12C ratio increases between 3500 BP and 3400 BP, a sample deposited in 3500 BP will have less 14C at the time of deposit than a sample deposited in 3400 BP at the time of deposit, and in addition as it's 100 years old the 3500 BP sample has had another 100 years to decay. So there will be less 14C when tested today in the 3500 BP sample than in the 3400 BP sample -- in fact more so than would be the case if the ratio were steady over that century. This corresponds to a steep part of the curve, rather than a plateau. Mike Christie (talk - contribs - library) 21:34, 11 August 2022 (UTC)

I've tweaked the footnote again. I didn't like when the level of 14
C in samples remains constant. New text: "A plateau in the calibration curve occurs when the ratio of 14
C/12
C in the atmosphere decreases at the same rate as the reduction due to radiocarbon decay in the sample." - Aa77zz (talk) 08:19, 12 August 2022 (UTC)

I see why you changed it. I was trying to get the reader to see that a decrease in environmental 14C would lead to samples of different ages having the same 14C level at the same time. Per the discussion with Dudley above it's not intuitively obvious why a falling 14C/12C rate leads to a plateau, but it's probably too complicated to explain in a footnote. Mike Christie (talk - contribs - library) 12:11, 12 August 2022 (UTC)
  • Indeed the concept of a radiocarbon plateau looks too complicated to fit in a footnote, that's why I mentioned "article body" at the thread start (personally, I believe it would be good to write at least a paragraph or even a separate section on this issue somewhere). Ain92 (talk) 14:30, 14 August 2022 (UTC)
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