Talk:Radiocarbon dating/Archive 2

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Simplified archaeological sample age determination for laymen

New section deleted because:

• The heading was confusing. Radiocarbon is used to date much more than archaeological samples, as said in the articles related to C-14. The reader would get the impression that the simplified method works only for archaeological samples.

The simplified calculations proposed have a granularity of one half-life, i.e. 5730 yrs. This gives the reader a false impression re the real precision of the method when seeing dates quoted with a +/- statistical error of, e.g., 100 yrs. BTW, such coarse method is described in the article about radiometric dating, see [1] Jclerman 01:38, 26 June 2006 (UTC)

I have written another trial version of the 'simplified calculation bit with perhaps a bit more explanation/derivation, see User:Vsmith/Dating calc - comments? The method gives the same dates (w/in about 0.1 yr) as the standard formulae that seems to intimidate some readers in the section Computations of ages and dates of this article. Vsmith 15:30, 26 June 2006 (UTC)

I looked at the method on your user page, but it seems like verbiage. Also, the formula is not that important, because you really have to calibrate the ages (via tree rings). You are probably right that the formula unnecesarily intimidates people though. Perhaps the discussion of the formula should be improved. Also, I like the example that you give at the end on your user page: 2 half lives * 5730 yrs/half life = 11460 yrs; this is easy to understand and should help people who have trouble with the formula.

—Daphne A 16:23, 26 June 2006 (UTC)

I also looked at Vsmith's proposal. I tried to shorten it but, in fact, I got it longer. I made some punctuation and other minor changes that migth be incorrect or unwanted... (It's at User:jclerman/Dating calc.) True, we do dendro calibration, but we need a raw date to input into the calibration curves, and the readers might want to know how do we get the number/date we input. Perhaps the table could have an extra row with the corresponding dates for each fraction, thus avoiding the mystery of the logs... Jclerman 23:27, 27 June 2006 (UTC)

Looks good. This is the way I introduce the concept to my beginning high school Chem 1 students as they haven't been exposed to rate laws and such and this is easier for them to grasp. I use base 10 logs for them as it's easier for them to grasp (most don't know what logs are) and with a brief intro they can use another button on their calculators :-). The example giving non-integer half lives is important as it is simply the most common real world outcome (I just picked a random fraction off the top of my head there). Probably should convert the table to a wiki table from the HTML one I made if it is a go. Cheers, Vsmith 02:01, 28 June 2006 (UTC)

Okay—my suggestion is that the new text replace, rather than supplement, the current explanation, except keeping the first sentence of the current explanation.

You said that "we need a raw date to input into the calibration curves". We need the raw 14C measurement, true, but we do not need to do the exponential calcuation. Rather, the raw 14C measurement can be directly compared with the raw 14C ages in tree rings (it is actually easier this way, because then the distributions are true Gaussian).

—Daphne A 04:19, 28 June 2006 (UTC)

Thanks to Vsmith and Daphne A for your useful comments. I'll be considering them when I make some minor edits to the sections in discussion. It will be later, probably overnight. Thanks again. Jclerman 17:41, 28 June 2006 (UTC)

My suggested Note, still rough, in progress, etc. is ready to be viewed at User:Jclerman/Dating calc.--Jclerman 16:18, 29 June 2006 (UTC)

Attn Vsmith: I wonder if you could put a webcam in your classroom. We would not only learn something, but we would avoid convoluted discussions ;-). I destroyed a little more your table, examples and text. See suggestions that I included between [] (I am not familiar with table editing, neither wiki or html). See also my comments below. And your non-integer n is a great idea. See my suggestion for an extra example with a larger n. --Jclerman 16:18, 29 June 2006 (UTC)

OK, I converted the table to wiki format with an online tool ([2] wow was that easy) and added the age (year) row. Also added one more column - just cause it would fit :-) Note, I removed the cell borders as it gives a "cleaner" look, but can set it back to one if preferred. The only problem I find with using the "easy" method is that my advanced chem students want to use it rather than the "book" rate constant eqn. - hey they learn :-) I try to have them also work with fractional values of n also, even had my adv students calculate how many C-14 atoms decay per second in an average human, one second is a very small fraction of 5730 years. Interesting result 'tho I can't say how accurate. Cheers, Vsmith 02:57, 30 June 2006 (UTC)

Attn Daphne A: I failed to understand your statement: We need the raw 14C measurement, true, but we do not need to do the exponential calcuation. Rather, the raw 14C measurement can be directly compared with the raw 14C ages in tree rings (it is actually easier this way, because then the distributions are true Gaussian). Can you please explain this method and give a reference to it?. Since to use calibration curves one needs to input a raw age or raw date value, I've expanded my current draft in progress to explain the experimental procedures to obtain such value before using a calibration curve. One of my problems was not to understand what do you mean by raw 14C measurement (activity?, age?). Other statement I couldn't parse is: the raw 14C ages in tree rings. How different is this from a calibration curve? I'll be glad to delete/edit/merge relevant statements in the article's Note as soon as I understand your method without the exponential. --Jclerman 16:18, 29 June 2006 (UTC)

To me, the proposed new text looks too complicated. Many people will not understand it; among those people that do, they could find out what they need from the article on Exponential decay (which is linked to from this article). I preferred your previous proposed text!—as a replacemnt for the current text.

As for the term "raw", I'd used this because that is what you had used. In any case, one problem with reporting radiocarbon ages is that they are not true Gaussian (for example, 15000±50 is usually considered to be Gaussian, but in fact it is log-Gaussian). As for tree rings, suppose that their (¹³C-normalized) activity levels are measured to be m1±s1,m2±s2,m3±s3,...,mk±sk; and suppose that we have a sample whose activity level is m0±s0; then it is clear that we can interpolate the tree-ring activity levels and calibrate the sample measurement directly against the interpolated curve. So we do not need to use exponentials.

—Daphne A 09:42, 1 July 2006 (UTC)

• I don't think I've used the expression "raw C14 measurement" unless I was quoting you. Notice that I would not know what it means. I use "raw C14 date", "raw C14 age", "calibrated (calendrical) C14 date", "raw C14 (radio)activity", "net C14 (radio)activity", etc. Notice that only the "raw activity" is the result of a primary measurement. All other quantities are calculated.

The first time that the word "raw" was used was in your posting at 23:27 on June 27. I actually don't know what "raw" means in any context. Anyway, though, I think we might be better off letting this subject drop, and I will agree not to use "raw" anymore. —Daphne A 13:24, 8 July 2006 (UTC)

• The "Note section" in the article and its current draft proposal are not intended to be a main section of the article. In fact, they grew up during six months of extensive exchanges with users from varied backgrounds. It still keeps growing in length due to the need to define the quantities we are using. Once we agree about what we all mean, it could be trimmed down.
• I still do not understand how can you avoid the exponential to obtain a "calibrated (calendrical) date" from a "raw C14 age". To understand what you mean I need to know what is that you measure. what dendrochronological information you use, the physical measurements you perform and the ensuing data processing.

Okay, here's a simplified example. Measure the (¹³C-normalized) activity levels of tree rings from the years AD 500, 510, 520, 530, ..., 800. Also measure the (¹³C-normalized) activity level of the sample that you want to radiocarbon-date. Suppose that the sample has the same activity level as the tree rings from AD 700 (and a different activity level than all other measured tree rings). Then the sample must be from about AD 700. And if the sample has an activity level between the activity levels of rings from AD 700 and AD 710, then the sample is from sometime between those two dates. (There are details that I've left out here, but I hope the example illustrates the main idea okay.) —Daphne A 13:24, 8 July 2006 (UTC)

• You might be referring to a new or unsourced method, which even if it could not be incorporated in the article (by Wikipedia policies) it would be valuable to explain within this discussion space for the benefit of radiocarbon researchers.

--Jclerman 19:06, 5 July 2006 (UTC)

This is the method that seems to be described—albeit briefly in the last paragraph—at http://www.informath.org/Basic14C.pdf (one of the External links for this article). There should be better sources. —Daphne A 13:24, 8 July 2006 (UTC)

To me it seems to be a simplification for teaching purposes, like the use of isotope abundances (in parts per trillion) rather than measurements on basis of the percent modern, as it is done. I am describing how it is done in the following. I fail to see the advantage in reconverting data from ages to activities, though. See below: --Jclerman 01:36, 11 July 2006 (UTC)

I agree that it seems to be for teaching purposes, rather than explaining how calibration programs actually work. Which is better for Wikipedia? (This is a serious question; I'm not really sure.)

Regarding what you wrote below, it mostly reads nice and clearly! The explanation for 13C could be clearer, I think. Also, the text does not account for AMS labs, which can use milligram amounts of carbon. And it is untrue that trees are from many latitudes: there is little equatorial, for example.

—Daphne A 11:46, 14 July 2006 (UTC)

Each simplification done for the sake of teaching later requires longer add-ons. It would be senseless to sample Equatorial treerings because most if not all species grown in such latitudes do not have annual rings since there are no marked seasonal variations and, anyhow, because the Equatorial masses of air are a mixture of Northern and Southern Hemisphere air. The article states clearly that corrections or normalizations for isotope fractionation have not been included (yet?). Where is the limit between an article and a how-to manual? Decontamination of samples for extraneous carbon has not been described either. My below discussion of calibration clearly refers to (radio)activity (detection)counting, thus AMS was not mentioned. Anyhow, when the collection of samples with potential dendrochronological+radiocarbon value was made, AMS had not yet been foreseen. --Jclerman 12:18, 14 July 2006 (UTC)

Yes, equatorial trees do not have annual rings—that was my point: it indicates that the proposed statement about "diverse latitudes" is misleading. Activity levels are determined by AMS. The paragraph about "grams of wood" seems to be irrelevant here and potentially misleading. Also, the part about "protected species" is new to me; are you refering to bristlecone pine? —Daphne A 07:00, 18 July 2006 (UTC)

1. "Diverse latitudes" is not misleading. Have you seen the list of the different localities, continents, elevations, in N and S Hemispheres from where tree sections were collected?

2. AMS is mass spectrometry, it does not measure activities. It counts atoms which have not yet disintegrated: it measures in units of "number of [undecayed] atoms" which are collected in a "cage" or "cup" whereto they are deflected. The earlier method of (radio)activity counting detects only the atoms at the moment they are disintegrating: thus it measures in units of "dpm" as registered in a "counter" (proportional or scintillation).

3. "Grams of wood" is neither irrelevant nor misleading. Lets the reader infer the non-trivial task of chiseling wood from a tree section to obtain suitable amounts of wood that were used for "points" on the calibration curves.

4. "Protected species" lets the reader infer that "tree rings don't grow on [free and easily available] trees". FYI, bristlecone pine is not the only such species used for calibration because it grows in very restricted localities. Calibration of the radiocarbon scale had to rely also on S Hemisphere and European trees.

--Jclerman 07:44, 18 July 2006 (UTC)

A non-specialist might well tend to think that "diverse latitudes" includes non-temperate latitudes. Activity levels can be determined from AMS measurements (think about it). What does it matter if conventional radiocarbon was used for most of the calibration measurements?—and I think that AMS was used for a few of the measurements that went into INTCAL04 (though I'm not certain). It is potentially misleading because without more discussion readers might think that grams are always necessary. Many of the trees used for calibration are readily-available oaks; I don't think that they are protected. The problem with the oaks was not that they were/are protected, but rather that they had died a long time ago and had to be retrieved from bogs, etc.

Maybe the root of our apparent disagreement is over how much detail should go into this article. My view is that too many details obscure the central points and leave readers more confused than enlightened. Possibly a compromise would be to include many more details even than you are suggesting, and put that in a separate article?—just an idea.

—Daphne A 09:31, 18 July 2006 (UTC)

About calibration

• Radiocarbon dating analyses are destructive. This means that the wood of treering samples is combusted to produce carbon compounds (carbon dioxide, benzene, etc) whose [specific raw (uncorrected, unnormalized) radio]activity can be detected by counting its disintegrations per minute.
• To attain the appropriate precision and accuracy, the determination of such raw activity requires grams of wood and weeks of counting its radioactive disintegrations.
• The computation of the net specific activity of each sample requires extra weeks analyzing background ("dead" radiocarbon) and modern ("AD1950") standard samples, then to be normalized to a standard C13 value.
• The raw radiocarbon ages are evaluated from the standardized specific net activities described above.
• The series of treerings to be dendrochronologically & radiocarbon dated to be used to calibrate the radiocarbon dating scale were the result of decades of explorations begun in the early 1960s. Remote sites were explored at diverse latitudes and elevations, searching for unique rare, living and dead millennary trees to obtain suitable samples. They were mostly from protected species.
• All the determinations of the radiocarbon activities described above have been cross-correlated and preserved as calibration curves (or tables). By definition a calibration curve has quantities of the same kind on both axis, namely calibrated dates (given as Calendar Years) on the horizontal axis and raw ages (given as Before Present years) on the vertical axis. See Example 1.
• Should a conversion curve be preferred, rather than a calibration curve, the ages on the vertical axis can be converted to the original radiocarbon activities by a simple mathematical operation.
• Any radiocarbon activity from a sample to be dated might match the radiocarbon activities of more than a single tree ring. In Example 1, the sample whose activity dated as 900BP old matches 5 different calendar dates which were obtained from 5 different dendrochronologically dated treerings.

File:C14dendro.jpg

Example 1.

• In practice, things are complicated by the statistical uncertainties (a) of the curve itself, which is really a band, (b) the uncertainty distribution of the sample's activity, and (c) the non-monotonic character of the calibration band. Graphical examples covering the statistical uncertainties and their propagation are given here [3] and here [4].

--Jclerman 01:39, 11 July 2006 (UTC)

---

Constant cosmic ray flux assumption

Since it is assumed that the cosmic ray flux is constant over long periods of time, carbon-14 is assumed to be continuously produced at a constant rate and therefore that the proportion of radioactive to nonradioactive carbon throughout the Earth's atmosphere and oceans is constant.

I'm pretty sure the above is false since:

Beryllium 10 is useful for studying the geology from hundreds of thousands of years ago mainly because it has a half-life of about one and a half million years. In addition, there are two key factors that have affected beryllium 10 production over the last 200,000 years: the earth's magnetic field and the sun's magnetic activity. When there are high-intensity solar magnetic storms, more charged particles are interacting with cosmic rays, and less beryllium 10 is produced. Likewise, the earth's magnetic field changes the flux of cosmic rays into and out of the atmosphere. EurekAlert

-In response to the above: The solar storms only cause a cosmic ray influx in the short term, in the long term it's either negligable or included as part of the average rate of production.

-In response to the above: The current rate of C14 decay is not as large as the current rate of C14 production (differences of 15-30% are quoted).

-Because of calibration curves, this assumption doesn't have to be true for C14 to accurately measure the age of an object (I've added this statement to the article). Samboy 20:50, 11 Apr 2005 (UTC)

-The assumption that the relative isotopic abundance of C-14 is constant was successfull for the development of the method, but is only approximately true (this is the reason why one needs calibration curves). Variations of cosmic radiation and of reservoir exchange rates have influenced the atmospheric radiocarbon abundance. Deviations of about 10% during the last 10,000 years are visible in the calibration curve, 26,000 years ago the relative radiocarbon abundance was even 60% higher (column "Delta 14C" in http://www.rlaha.ox.ac.uk/O/intcal04.14c). --Peter.steier 18:41, 14 September 2005 (UTC)

Calibration curves as basis for dating

Is it your position that the calibration curves are the basis for radiocarbon dating accuracy? If so, then what is your position on the bristlecone pine measurements that I posted in the dendrochronology talk page? Wdanwatts 02:27, 12 Apr 2005 (UTC)

My position is that the assumption that C14 levels have been fairly constant is a reasonable starting base for dating items. However, this assumption is not necessary because of the existance of calibration curves. Basically, we get almost the same namers from calibration curves that we get from just assuming that C14 levels have been constant for the last 10,000 years. We have two independent ways of getting at the same data. The chances of both methods giving us mostly the same data by pure chance is really small. Samboy 02:36, 12 Apr 2005 (UTC)

Is not the fact that the calibration curves make "small" corrections sufficient to ensure consistency between the results with or without "calibration"? How does that bolster the results? Dan Watts 13:51, 16 Apr 2005 (UTC)

About the graph on Bristlecone data posted to the dendrochronology discussion, note that zero widths can't be measured. They mean missing rings as inferred from comparison of patterns in several cores. Thus, the graph is not relevant to the discussion. Jclerman 20:35, 3 October 2005 (UTC)

Standard deviation

Is is really the standard deviation that is indicated by +/- ? That should indice the e.g. 95% confidence limit. The difference is (at least) a factor of two!)

It is as is common with all publishing of measurement results. And it is not the error of the dating but only that of the ¹⁴C content of the purified carbon actually being measured. I have just written a paragraph about that in the German version of the article. - Axel Berger 14:57, 6 January 2006 (UTC)

Kudos

Great article! --Yak 16:50, Feb 22, 2004 (UTC)

Calibration Curves

Please educate me as how speleothems (which appear to mainly use U/Th means for dating) can be used to calibrate C14 dating. It looks like using a yardstick to calibrate a micrometer. Wdanwatts 18:35, 13 Apr 2005 (UTC)

Speleothems, at least some of them, have layering due to variations in seasonal precipitation, etc. The calcium carbonate of the speleothem uses CO2 from the air & water. The older end of the C-14 scale can be matched with the shorter end of the U-Th scale, presumably. The question I have here is the ancient carbon in the waters that was dissolved out of the limestone by the water on the way to the speleothem. Vsmith 20:35, 13 Apr 2005 (UTC)

As long as I am asking, how about some explanation of how the sources listed in the article --ice and deep ocean cores, lake sediment varves, and coral--, (all but dendrochronology) contribute to the C14 calibration. To me, the links look to have tenuous (at best) connections to C14 calibration. Wdanwatts 19:43, 13 Apr 2005 (UTC)

Ice cores have annual layers which are countable. The cores also contain inclusions of trapped air which contains CO2 and therfore C-14. Deep ocean seds and lake varves are layered sediments w/ presumably annual layering, these contain carbon within the seds that has C-14. Coral is built by organism in crude? layers and carbon is present from the corals. Correlate the layering - check with C-14 dates.

Hope this simple explanation helps, although there is a lot more in the details and I may have mixed things up a bit :-). Vsmith 20:35, 13 Apr 2005 (UTC)

Perhaps you could put that in the Ice cores article. It tells of needing 2000 to 6000 annual layers of snow to becom impermeable to air. I don't see how having an averaging factor that large can allow much calibration of the C-14 dates. Wdanwatts 12:51, 14 Apr 2005 (UTC)

Hmm.. just read that, and it does state that correlation problems exist. Looks like the ice core article is currently undergoing some revision by Tonderai with some references. More to explore there, cheers. Vsmith 13:57, 14 Apr 2005 (UTC)

There is a lot to explore there. When searching in the ice field of research, remember to also search for "firn" and "snow pit". (SEWilco 06:01, 16 May 2005 (UTC))

Question

Does this article address the fundamental fallacies of Radiocarbon dating? 1. Assuming that the rate of formation and decay of C14 have reached equilibrium? 2. Assuming that after two or three half lives the amount of C14 is still measurable?

This is nonsense. After one half-life, half the amount is left. After another half-life, half the amount of half the amount is left, that is 1/4 of the original amount. Whether this is measurable depends on what the original amount was. Why don't you just read the article? I guess you are a creationist? --Hob Gadling 11:15, August 1, 2005 (UTC)

I don't think it's nonsense at all, and I also think it's very interesting how the moment someone questions the popularity of Carbon 14 dating, that they are immedietly labelled a creationist. The situation you describe with carbon 14 decaying in a neat little pattern is entirely dependent on the object being dated resting in a closed environment or at least an environment which is exactly as old as the object in question. Carbon 14 is pretty much in everything, so if you've got something that is 5,000 years old in a room of stuff that is only 500 years old, that 500 year old stuff will get more carbon 14 than normal onto the 5,000 year old object due to the tendency for all particles to want to reach equilibrium in any volume, and your older object will date as a much younger one. If something is closed off in a container that is just as old as any object inside, then perhaps carbon 14 dating can be reasonably assured to be accurate, assuming whatever you've put into the container was brought into existance around the same time as the container and hasn't been polluted by anything else. Of course, pollution from other objects in carbon 14 dating won't compleatly destroy your dating, as the margin of error is only as wide as whatever the most carbon-14 filled thing is in an evironment. But on to the first person's other point, Carbon 14 is just plain not used reliably after, what, I think the article said 60,000 years? the amount of carbon 14 left becomes extremely small, I mean REALLY small, so measuring devices can get wide numbers, or just plain get crazy numbers. Sometimes it doesn't even need to be that old either, I seem to recall a story awhile ago about some clams being carbon dated as being dead for over 1,000 years, and they were still alive. Carbon 14 dating is not compleatly innacurate of course, but clearly it is not perfect and totally regular like an atomic clock, and I don't see how questioning the idea of carbon 14's perfect makes one far more likely to be a creationist, challenging this isn't destroying science, there are thousands of other ways to date things, many of which are much more reliable than carbon 14 dating. Homestarmy 00:19, 29 January 2006 (UTC)

All your questions, critiques, and objections have been answered and discussed at length in the references given in the article. The detailed explanations given there are much more complete and thorough than we could do in this column. Also, if there is a radiocarbon dating lab in your locality, you probably could join an organized group visit and get a direct view and understanding of the method. In particular they could "walk you" through all the chemical and physical aspects of sample decontamination. analysis. computation, etc using data from real samples so you could compute yourself their ages and so get an "insider's view". Jclerman 01:22, 29 January 2006 (UTC)

I looked in the article again, and it even comes out and openly admits that the dates with Carbon 14 cannot be used at face value over long periods of time in the calibration section, other dating methods and what they indicate about what was happening in other time periods must be used to get an accurate picture of what the Carbon 14 results mean, that doesn't sound like a compleatly accurate dating method if many other methods have to be used to get correct results, which all can be affected by outside conditions in their own rights. But anyway, the original starter of this topic asked about the fundamental fallacies of Radiocarbon dating, and the reply given was that since Carbon 14 always perfectly decays on a certain half-life, (Which it does, im not challenging that) that requiring the object to have equilibrium between formation and decay and requiring the object to have a measurable about of Carbon 14, is nonsense. Personally, I don't know anything about that first thing, and I think I might of jumped the gun and addressed a compleatly different critisism, so um, sorry about that, just ignore the first part of my comment. But on the second part, admittedly, it seems that whatever that new scanning thing they developed that I saw in the absolute dating article would let you read much less Carbon 14 content, so perhaps I was too aggresive in attacking that age, though it does make one wonder why those low dates are still in the article. However, even that has to have an upper limit on age reading, so I don't see how requiring a close to measurable content of Carbon 14 is nonsense, and in the second half of my comment I pointed that out, it doesn't make any sense to call requiring something to be measurable nonsense! Homestarmy 01:56, 29 January 2006 (UTC)

Come on, people. At least have the intellectual honesty to link to the already existing wikipedia entries on the creationism debate. I am adding a sentence about it. User:PhatJew

Intellectual honesty? Don't know 'bout that. Moved the irrelevancy out of intro for now - push the creationism POV elsewhere. Vsmith 12:32, 2 February 2006 (UTC)

LOL. Not my problem. I'll let the NPOV people deal with you.User:PhatJew

Now that a line was added to state the creationist objections against the method, I see no reason to qualify the neutrality as disputed. I vote to remove the "disputed" banner immediately. −Woodstone 13:45, 2 February 2006 (UTC)

Agreed. Done. Vsmith 14:15, 2 February 2006 (UTC)

Controversy

Carbon dating is often criticized in creationist circles as unreliable. I believe this is due to some cases in which the method yielded results that were later effectively disputed (possibly because the carbon dating made a constant cosmic ray flux assumption), but I don't know enough about this to be sure.

I think it would be a valuable addition to this article if some mention of these arguments were made, preferably with counterarguments. Anyone more knowledgable than I am willing to take this up? Great Cthulhu 16:29, 1 September 2005 (UTC)

The cases were not disputed because of cosmic rays, they were disputed because the creationists who cited them did not understand carbon dating. For example, they thought that dating the shells of living molluscs is relevant for evaluating the method. [5] --Hob Gadling 13:38, 29 September 2005 (UTC)

Further, I posit that if any of that ilk really wish to put up or shut up on their ideas, they can make a "What's wrong with anything that says the Earth is older than I say it is" entry, and failing that, they'll start shitting up this entry on their own accord. Part of the spooky-action-at-a-distance of NPOV is dialectical, isn't it? Opposing points of view will somehow find a stable equilibria or whatnot? Let's not violate that principle by trying to present the point of view of someone who wishes to destroy all understanding of radiocarbon dating with a false controversy. They'll be in here soon enough as it is. --Mayor Of France 18:49, 3 October 2005 (UTC)

Mayor Of France, I have yet to make up my mind on this (potential?) controversy. However, what is wrong for having people provide (valid) counter-arguments? Would it not be better for all parties involved to fight fair with sturdy facts, instead of engaging in "piranha attacks" as you have started to do? What benefit is there to raising the decibel level on this discussion? Surely, one would hope that the end result is that Wikipedia would come up with an article that can stand the test of time from rational people.

FWIW, no one has yet to posit the trollish "What's wrong with anything that says the Earth is older than I say it is?" argument. Surely, there are enough reasonable people here that will keep at bay those seeking to "...destroy all understanding of radiocarbon dating with a false controversy..." Are you saying that it is a false controversy simply because you have deemed it as such?? Perhaps you are of the opinion that Creationism/Intelligent Design advocates are predisposed to being disagreeable? If that is the case, it seems it has yet to present itself here. Please refrain from assuming the worst and give this debate a chance to be fair.

To date the only source of criticism of this technique has come from the young earth/creationism types. To elevate their unscientific attacks to the level of 'controversy' is to give them more status than they are due. As in most areas of science where their ideas cannot find traction, this group is now stooping to trying to inject the false impression that there is some internal debate in the field, thus providing a foothold for doubt. Doubt that they hope to exploit to foster their own interpretation of events. DV8 2XL 17:50, 10 December 2005 (UTC)

"what is wrong for having people provide (valid) counter-arguments?" Nothing. The problem is: there are no known valid counter-arguments, but a humongous heap of invalid ones. Every time a creationist (or ID person) presents a counter-argument (against evolution, natural selection, common descent, an old earth, or dating methods), it turns out to be based on ignorance or duplicity (hard to tell which). That's my experience. --Hob Gadling 19:36, 11 January 2006 (UTC)

Regardless of whether we agree or disagree on the validity of the controversy surrounding Radiocarbon dating, it is a fact that it exists (in a substantial amount). Therefor, a section should be added to the article detailing the various controversies. --Gregoryg72 12:53, 15 June 2006 (UTC)

I've noticed some incendiary comments in this thread opposing validation of young earth creationist arguments as controversy. Well, controversy is dependent on the existence of disagreement, not on the validity of an argument. No matter how invalid an argument is (in our Point Of View), there is a controversy as long as there is argument. And clearly, there is argument. However, that argument doesn't belong in this article, it touches on issues that are outside the scope of this article and the expertise of its contributors. We don't want to shift attention away from radiocarbon dating.

Rather than trying to describe the controversy in this article, it may be preferable to add a small section and paragraph marked 'controversy', indicating that radioactive dating methods are disputed by people who believe the earth is younger than it is shown to be. A more detailed discussion of this should be stored in a linked separate article named something like 'Radioactive Dating Controversy'. I believe Mayor Of France hinted at taking this approach.

How about the following for the paragraph:

"The accuracy of the radiocarbon dating method is disputed by those who believe the earth is younger than thus shown, particularly by Young Earth creationists. This is further discussed in the article Radioactive Dating Controversy"

This approach accomplishes two goals:

1.) It keeps this article focused on the issue at hand (radiocarbon dating, not religion). After all, the number 1 reason for young earth creationists to believe the earth is younger than radiocarbon dating suggests is that the Bible says so.

2.) 'Radioactive Dating Controversy' can be linked to from other articles (radiometric dating, radioactive dating) in a similar fashion, hopefully saving other wikipedians from constantly having to strip out NNPOV remarks.

Are there any reasonable arguments against this approach?

jdbartlett 01:49, 21 June 2006 (UTC)

Radiocarbon dating is science, and there is no controversy within science. Rather, there are people whose religious beliefs lead them to deny radiocarbon dating. Perhaps an analogy is useful: there is no scientific controversy that Earth revolves about the sun, but there are nonetheless some people whose religious beliefs lead them to deny this.

In other words, if you want to have an article in Wikipedia discuss the lack of belief in radiocarbon dating, that's fine, but the discussion belongs in an article on religuous beliefs. The discussion does not belong in an article on science (such as this one). If you started including anti-science religuous beliefs in scientific articles, you would have to do it for virtually all scientific articles: those that talk about Earth revolving about the sun, about the nature of the Moon, about the causes of winds, about how children are conceived, about ... just about everything. That is just not viable. Almost everything in science is disputed by some religion. So the place to describe such a dispute is in the article on the religion that disputes it.

—Daphne A 04:21, 21 June 2006 (UTC)

Thanks for your response. I agree entirely with your appraisal. That any 'controversy' is a religious matter and not a scientific one is exactly why I am proposing the creation of a separate 'radioactive dating controversy' article where the religious response toward radioactive dating can be handled. Once complete, the new article can be linked to from this ('radiocarbon dating') article so those seeking information on radioactive dating's effect on religion will know where to look. The place to describe the dispute (beyond acknowledgment) will indeed be in the article on religion that disputes it and not in this article.

The evolution article takes a similar approach. In fact, taking cue from the evolution article in labelling the linking section 'social and religious controversies' would be preferable as this would help the reader discern between religious and scientific controversy.

Does this approach seem reasonable or does it still require refinement?

jdbartlett 16:08, 21 June 2006 (UTC)

A separate article on radioactive (or "radio-isotopic") dating controversy is a fine idea. I can't imagine that anyone would disagree. My suggestion would be to then include a link to that article in the "See also" section of this article: others might suggest a different approach, but that is irrelevant for the writing of the new article. I hope you will do it!

—Daphne A 05:38, 23 June 2006 (UTC)

Thanks again for your response. I've started work drafting the article and hopefully should have something ready over the weekend. Interestingly, I discovered this while digging around: [6] I'm not sure how opinionated the deleted article was (probably quite, judging from the one-word comment "lol") but I'm still worried my article will suffer the same fate based on the number of votes to merge or delete controversy on... by reasoning that radiometric dating is treated in its own article. I've started work on an anticipatory Justification section for my article's Talk page which will mostly reiterate what we've discussed in this thread.

jdbartlett 09:40, 23 June 2006 (UTC)

Perhaps the way to do it is to entitle the new article "Religious-based controversy over radiometric dating", or something similar. There definitely is a religuous controversy, and an inclusive encyclopedia should mention this. Similarly, there were apparently some native Americans who, for religuous reasons, didn't want certain people to go to the moon; again, this has nothing to do with science, but it is a religious belief that deserves mention in an inclusive encyclopedia, even if most people (including me) find their religuous beliefs silly. The new article could even take a sort of anthropological approach (just as an article on the natives and the moon might).

—Daphne A 12:14, 23 June 2006 (UTC)

I saw DaphneA's comment above "Radiocarbon dating is science, and there is no controversy within science." and it reminded me of an article I read recently, which can be found at http://www.crichton-official.com/speeches/speeches_quote04.html. The article is called "Aliens Cause Global Warming" which is rather tongue in cheek, so don't let it scare you off. I myself am a student of history, not science and I am content to wade in the shallow end of the intellectual pool with my water wings and PFD on. Nonetheless, I can't agree with the contention that there is no controversy within science, as this article clearly illustrates. Further, in many, if not most, areas of science, in particular physics I believer, we are still hampered by an inability to know absolutely everything. This of course means that in many instances we will only achieve the 75% solution, when the little tidbit of information we lack could lead us to completely different conclusions. While I am at a loss at this late hour to provide an example, I am quite sure that through the ages there have been a myriad of "facts" that science agreed upon which were later unproven. This leads me to believe that any contention that tere is no controversy within science is patently false. Of course this discussion is not a debate on the existence of controversy in science but on whether or not a section of controversy should be included in an article on radiocarbon dating. If the world truly lives in a balance, there will never be a theory without a counter-theory. The controversy surrounding radiocarbon dating is just as much a part of the theory as the science is, and should therefore be included for the reader to make up their own mind, placing each in context with the other.

Sorry for the ambiguity. What I meant was that there is no controversy within the science of radiocarbon dating. Also, there actually are controversies about radiocarbon dating within the science (e.g. location dependencies), but the specific controversy being discussed here is religious. —Daphne A 07:04, 18 July 2006 (UTC)

Can you please give a list of the "radiocarbon science controversies", and also clarify what do you mean by "location dependencies"? Please, include relevant references so we understand what we are talking about. --Jclerman 07:51, 18 July 2006 (UTC)

A good place to start is with F.G. McCormac et al., "Location-dependent differences in the ¹⁴C content of wood", Radiocarbon 37: 395–407. Then use Google Scholar (or Science Citation Index) to find papers that cite that. —Daphne A 09:14, 18 July 2006 (UTC)

Introduction

Is there some reference for the recent change to the extreme limit of radoicarbon dating from 50,000 to 60,000 years? Dan Watts 19:01, 22 September 2005 (UTC)

Yes, from a Google search:

COSMIC BACKGROUND REDUCTION IN THE RADIOCARBON MEASUREMENT BY SCINTILLATION SPECTROMETRY AT THE UNDERGROUND LABORATORY OF GRAN SASSO, by Plastino, W. et al. Radiocarbon, Volume 43, Number 2, 2001, pp. 157-161(5).

Excerpt: The cosmic noise reduction observed at the laboratory of Gran Sasso makes it possible to perform high precision 14C measurements and to extend for these idealized samples the present maximum dating limit from 58,000 BP to 62,000 BP (5 mL, 3 days counting). [7]

Impact on Archaeology

Is there any reference to substantiate this diatribe? Dan Watts 03:14, 25 September 2005 (UTC)

Removed here pending addition of references and cleanup:

== Impact on archaeology ==

Radiocarbon dating had a large impact on archaeology, particularly on many of archaeology's theoretical assumptions until this tool was introduced after World War II. In effect, radiocarbon dating established that many artifacts are now known to be far older than previously thought, and thus going back to earlier ages than otherwise could have been if they had been only the inspired and diffused products of the Near Eastern civilization. Therefore, the notion that the ancient Near East was the fount of global human civilization can no longer hold true. Clearly, various centers of civilization arose independently of one another even if the Near Eastern one remains the oldest on record.

Vsmith 15:35, 29 September 2005 (UTC)

Basics

An anon person said "There is also another way of finding the absolute date of something using radioactive dating. First, find the fraction of un decayed material and find out how many times you have to multiply it by itself to get the fraction (n). In Example: 1/8 of the parent material is left. you would need to do 1/2 * 1/2 * 1/2 to get 1/8. Therefore, the n would equal 3. Secondly, you multiply n * (one half life in years)= Age in years"

1. If this is another way, which one is the "other"?

2. The materials don'd decay. The radiocarbon atoms in the material decay.

Jclerman 03:19, 23 November 2005 (UTC)

Yes, I was going to remove that - you beat me to it :-) Seems to be quite simplistic and contains a couple of confusing errors. Doesn't really belong here and I assume the subject is better covered in radiometric dating, at least I hope it is :-) Vsmith 03:40, 23 November 2005 (UTC)

Nitrogen: Molecules or Atoms?

In the equation with a neutron bombarding a N-14 atom to produce a C-14 atom plus hydrogen, one would assume that it is indeed the atom and not the molecule involved in this reaction.

However, there is a statement about 80% of the atmosphere being nitrogen, but doesn't that refer to the molecular form and not the atom? What is the actual percentage of monatomic nitrogen in the atmosphere? Kenny56 07:39, 20 December 2005 (UTC)

The amount of monatomic nitrogen in the atmosphere is likely to be rather small. However, since the neutron energy necessary to bombard N-14 into C-14 is large, the electronic configuration would have a vanishingly small effect on collision cross-sections. Dan Watts 13:18, 20 December 2005 (UTC)

Whoa now Dan, where did you come up with large neutron energies being necessary for N-14 into C-14? Do you know this to be true in fact? You seem to have spoken in excess of your knowledge on this subject, which severely damages your credibility. Look up the isotope 14 of carbon and how it is created, then look up the energy of thermal neutrons. Kenny56 07:25, 27 December 2005 (UTC)

Well, I guess that knowing that the free neutrons came from cosmic ray interactions is not sufficient to determine their energy. Mea culpa. Dan Watts 02:43, 9 January 2006 (UTC)

Don't be too shy about that. Unless someone can pinpoint a source of thermal neutrons in thin upper atmosphere, I'd say there aren't any. Thermalizing neutrons in the short time they have before decay or absorption is not an easy thing to do. - Axel Berger 07:42, 9 January 2006 (UTC)

Nitrogen appears to have the highest covalent bond strength of all the diatomic molecules, so it has a high affinity to bond or stay bonded with itself, which explains why the concentration of monatomic N is so low. The article needs to reflect the correct nitrogen species and concentration in the atmosphere.

The next questions that comes to mind are how the C-14 bonds to oxygen to form the CO2, does it gather two oxygen atoms or glob onto an O2 molecule? And, would the free Hydrogen atoms created with C-14 seek to form H2 molecules and/or compete with the C-14 for the available oxygen atoms/molecules in forming water molecules? Kenny56 07:30, 27 December 2005 (UTC)

This thread appears not to be related to the techniques of radiocarbon dating. Experts on this topic are probably available in one of the cosmochemistry or nuclear chemistry discussions. Jclerman 18:33, 28 December 2005 (UTC)

What's up with the bold print? I would expect that the experts in the techniques of radiocarbon dating would also be experts in the simple chemistry upon which the techniques rely, or at least have the knowledge to explain the basics, would they not? If you can contribute to the discussion then please do so, but feel free not to chime in if you can't.Kenny56 08:23, 7 January 2006 (UTC)

I just happened to wonder about this same question and found a recent thread discussing it here. I'm not sure I understand the answer. Are you saying that the nuclear reaction takes place on an N atom in an N2 molecule, which then splits up into one N and one C? These parts then subsequantly recombine in the environment into new N2 and CO2? Adding this to the article would make the picture more complete. Woodstone 22:33, 29 December 2005 (UTC)

A neutron does not interact at all or only negligibly with the electrons. From the point of view of the neutron there is no difference between a bound or free atom or one in an ionized state. All that matters is the cross section (physics) of the nucleus for the reaction of interest. Axel-berger 17:29, 5 January 2006 (UTC)

Thanks for the above observation. Sounds clear. So then we get a molecule of CN. Is that chemically stable? Or does fall apart in N and C atoms right away? −Woodstone 21:26, 5 January 2006 (UTC)

No probably not. I do not know what energy the proton in the conversion is emitted at, but typically nuclear binding energies are so much higher than chemical ones that the recoil ought to break the molecule apart. You're left with two ions or radicals and the rest is simple atmospheric chemistry.Axel-berger 14:10, 6 January 2006 (UTC)

According to data found on other wiki pages, the free neutron absorbed by the nucleus of the nitrogen atom to produce the C-14 atom is known as a thermal neutron and has an energy of 0.025 eV. The diatomic nitrogen molecule has a triple covalent bond with a bond energy of 946 kJ/mol, or 9.79 eV. BTW, a CN molecule is also known as cyanide, which is toxic to mammals. i'm still searching for answers to the simple atmospheric chemistry questions, but not finding much to fill in the gaps.Kenny56 08:23, 7 January 2006 (UTC)

When I said "simple atmospheric chemistry" I did not mean it was simple as such, but extraneous everyday stuff that need not concern us here. Do not forget we're talking about a concentration of 10^-12 (one part per billion or in America even only one part per trillion) of atmospheric carbon, or 0.4x10^-15 of atmospheric gases. Chemically any of its compounds are totally irrelevant and in equilibrium they'll all end up as CO2 anyway. - Axel Berger 23:44, 7 January 2006 (UTC)

Actually I do not know a lot about that reaction - the ones I've been taught are those relevant to power plants. But I'm pretty certain there are few thermal neutrons up there, you need a lot of dense stuff like water or carbon with a very low absortion coefficient for them to bounce off often enough to thermalize (lose very high initial kinetic energy down to thermal equilibrium) without vanishing. But even if your numbers are right, they're irrelevant here. The interesting bit is not the purely kinetic energy of the incident neutron before the reaction but the energies set free by the nuclear reactions themselves. What you need to look up, if you have sources to hand, is the typical energy of the emitted proton.

The one thing I have found is that 15N itself is stable, so it must be an excited state generated by the binding energy set free on absorbing the additional neutron into 14N that leads to the decay.

14N + n --> 15N --> 14C + p (= 14C + H)

I seem to have lost my nuclid table, but if you find the data, add the masses of 14N and a free neutron and subtract that of 15N, you get the energy released in the capture. - Axel Berger

Formulae

I wonder if the formulae at the end cannot be expressed simpler (without detour through natural log) as follows:

$N=N_{0}\times 2^{-{\frac {t}{t_{1/2}}}}$, resulting in $t={t_{1/2}}\times {}^{2}\!\log {\frac {N}{N_{0}}}$

−Woodstone 22:33, 29 December 2005 (UTC)

1. Something is amiss in this new expression proposed for t, if I test it by plugging in a simple N/No ratio of 1/2, I don't obtain the expected 5568 yrs BP.
2. What is gained by using logs base 2 rather than logs base e?

Jclerman 00:08, 30 December 2005 (UTC)

Sorry, I forgot t_½ (now added above). The advantage is no need for the extra parameter λ: only t_½ is used. −Woodstone 10:23, 30 December 2005 (UTC)

Insider information

1. Why get rid of lambda? The inverse of the constante lambda is a useful and well known value for a physicist. It's the mean or average life of a radioisotope. For radiocarbon its value is close to 8000 yrs [lambda is close to 1.2x10(exp -3)]. These easy values allowed us, in the "prehistoric" times of the development of the radiocarbon dating technique, to mentally evaluate approximated results (dates and their uncertainties) while a dating was in progress during the several days required. For example, from lambda's value it can be derived that 1% decrease in radiocarbon activity corresponds to about 80 yrs.
2. Why not log base 2? Because lambda's usefulness. Moreover slide rules didn't have base 2 log scales. During Libby's lifetime we used long slide rules with LL scales to compute radiocarbon dates. In fact the first electronic portable digital calculator which I saw was the one Libby showed us, as a novelty, from the podium in a Radiocarbon Dating International Conference, in New Zealand, in 1972.

by Jclerman 16:59, 30 December 2005 (UTC)

These are mostly historical arguments: we do it that way because we've always done it that way. How long since you last used a slide rule? I have seen "half life" much more fequently than "average life", so it would make sense to eliminate λ. However, if experts do it overwhelmingly with natural log, I will not insist further. Thanks anyway. −Woodstone 17:52, 30 December 2005 (UTC)

The thing I do not understand is why historically the half-life was chosen in the first place. At the time exponential decay was an old hat and a commnplace formaula to all physicists - see current in a coil or charging a capacitor. All these processes are governed by their time constant Tau, i.e. the inverse of Lambda. Why the first researchers into radioactivity did not choose this but something entirely new, unusual, and impractical is a mystery to me. Could it be because they tended to be chemists and not physicists and not used to mathematical calculations?Axel-berger 14:14, 6 January 2006 (UTC)

Earth's Magnetic Field Decay

The earth's magnetic field was measured by Gauss in 1835 and has been repeatedly measured since then showing an exponential decay with a half-life of ~1400 years. So it is likely that the earth's magnetic field strength was 8x higher just 4200 years ago. Would not this stronger field provide greater cosmic ray protection to the earth and possibly reduce the C-14 production rate from its current rate? Do the calibration curves take the magnetic decay effect into account? Kenny56 08:10, 20 December 2005 (UTC)

Calibrations are performed by comparing the known dates of a series of samples, with the corresponding radiocarbon dates. This bypasses the origin and the value of all factors that affect the atmospheric radiocarbon level. Jclerman 18:30, 28 December 2005 (UTC)

Essentially, the calibration curves take some other (assumed) temporal marker(s) {tree-ring dating, varves, speleothems, ice cores, etc.} and compare how the dating results from those methods align with C-14 dating technique result. So, specifically these calibration techniques ignore the earth's magnetic field strength since it is (usually) not necessary for such measurements as dendochronology (and except for theoretical computations, it doesn't enter into the C-14 dating calculation). However, if the C-14 production rate were affected, that SHOULD show up in the C-14 calibration (with the exception of dendrochronology, I don't know what source(s) of C-14 would be used for the cross-correlation). Dan Watts 20:27, 20 December 2005 (UTC)

The magnetic field does tend to change a lot over time, but it is totally wrong to extrapolate a recent trend far into the past. Incidentally the field broke down to something like a tenth of the current value around 38 ka ago. You can find that in the calibration as highly elavated ¹⁴C values at the time. This is just about the time of the demise of the Neanderthals in Europe. I am currently trying to find out by how much ground level radiation might have risen then and if that might have been enough to disrupt the biosphere. Probably not, but I do not know yet. - Axel Berger 15:05, 6 January 2006 (UTC)

Please explain the time units for "38 ka ago", what is ka? And what is the reference or source of this statement that the field broke down to 1/10 of the current value? Thanks, Kenny56 03:58, 7 January 2006 (UTC)

Let me guess ka is short for kilo-annus, a thousand years. −82.171.189.187 05:29, 7 January 2006 (UTC)

Yes, "ka" is the common notation for kiloyear. As to sources I can only cite recent lectures given by our in-house specialist Dr. Bernhard Weninger and recently by Prof. Dr. Pieter Meiert Grootes from Kiel. As to radiation killing off Neanderthals my former teacher of radiation protection, Prof. Hans Bonka of RWTH Aachen, has just told me I was spouting nonsense, same as I used to do back then. Apparently the atmosphere itself shields us so good that changes in the field do not matter down at ground level - flying spacecraft and international air routes is another thing. (And of course he backed that up with data and numbers I ought to have known - all from his lectures at http://www.lrst.rwth-aachen.de/vorlesungen/index.php.) - Axel Berger 00:07, 8 January 2006 (UTC)

Cyoub said: Obvious mathematical error. Show your work.

ATTN: Cyoub

• Thanks for your one liner comment. I've now tried to clarify the nomenclature and expand on the physics and meanings that determine the directions of the time arrows. You could have gained insight into the existing deficiencies by plugging in the halflife value, a simple N/No ratio of 1/2, and see that you obtained a result of -5568 which means a date 5568 BP years. Please, check the current version and let me know of further deficiencies observed. Jclerman 18:44, 25 December 2005 (UTC)

Total rework

I have just seen that there is at least one other contributor to the sister article in German here too. That article has been voted one of the "good articles" there. While it would be a lot of work incorporating that material here, a straight translation and replacement might be doable. Doing that we might also clean up the duplications that have crept into the German one. While in no way offering to do it all, I would do my share. Comments? - Axel Berger 00:17, 8 January 2006 (UTC)

The role of Hessel de Vries

C-14 dating was first presented by the Dutch professor Hessel de Vries, who applied it for archeological purposes. De Vries also did substantial work on the counting tubes and later showed that some of the assumptions by Libby were wrong, eg, De Vries showed that the C-14 content wasn't constant over time, the so-called "De Vries effect". Libby received the Nobel prize for his work in 1960, but many seem to feel that had De Vries not died in 1959, the two would have shared the Nobel prize. I think this article could reflect this, or at the very least credit De Vries for his contributions. [8] [User 80.213.165.75]

Corrections and amplifications:

The reference you quote is one of those already listed in the article. It is under its author: Engels.

Until somebody writes a paragraph about Hessel de Vries's contributions, the whole story is told by Willis in one of the references which had already been included in the article. Willis calls de Vries "the unsung hero of radiocarbon dating."

H. de Vries :

• Proposed, tested, and used a better method than Libby's for radiocarbon dating, using CO2 gas in proportional counters.
• His chemical preparation lines, electronics, etc. were cloned in all European laboratories in the late 1950s.
• He studied the variations of atmospheric radiocarbon in the Northern Hemisphere and hypothesized that they correlated with solar activity and climate change (probably the first oblique reference to the now known as global warming). He cited work by a Dutch meteorologist, Barendsen (?) which probably was related to the later known El Niño and La Niña "oscillations" in ocean temperature.
• His was probably the first C14 geochemical model including the biosphere and hydrosphere.
• He also did extensive archaeological (and geological?) dating including the study of the Piltdown hoax.
• He had also contributed with pioneering contributions to biophysics.

Feel free to elaborate on some or all of the above and include it in the article.

Jclerman 19:40, 20 January 2006 (UTC)

Request for content

Fundamentalist Christians often criticize radiocarbon dating as unreliable. If anyone is aware enough of all this to write a section about criticisms + scientific responses, I think it would contribute much to the article. --Pierremenard 00:12, 25 January 2006 (UTC)

[9][10]--John^DO|^{Speak your mind} 04:43, 25 January 2006 (UTC)

I might be able to write something about the criticisms, but very little on the scientific responses to those criticisms. The article touches briefly on it in the Calibration section - objections to Radiocarbon dating often centre around potential fluctuations in Carbon levels (for example, the assertion that due to the biblical flood, Carbon levels were abnormally high some thousand years ago. the If no-one else can help, I'll give it a shot. - Tim Macready 60.229.75.117

ratio of carbon-14 to carbon-12

I find confusing to use in some places "level" and in others "ratio of carbon-14 to carbon-12 ". Please choose one and use it throughout. Why?

1. A lay reader might not realize that they are equivalent.
2. If you ever have to participate in an oral discussion, you might find cumbersome to say each time "ratio of carbon-14 to carbon-12".

I prefer level. Jclerman 01:00, 3 February 2006 (UTC)

Hi. I just got here and quite like your page, it is much better tended than most other pages on geochronological methods. I would like to comment on the "level" vs. "ratio" issue that is being discussed. Although use of "level" is less cumbersome and gets most of the important meaning across (so in the end might be the best choice) it is not strictly correct. The "levels" (assuming this means something like "concentrations") of ¹⁴C vary with the cosmic ray flux, nuclear decay and absolute carbon concentration. The ratio of ¹⁴C to ¹²C, however does not vary with absolute carbon concentration (i.e., CO₂ concentrations). Therefore a sample of air with high CO₂ concentrations will have higher "levels" of carbon-14 although may have an identical ¹⁴C/¹²C.

Unless I have mistaken the use of "level" in this case, solutions include:

1. Defining and using the ?¹⁴C notation throughout. Note that this notation already appears on an axis of the graph, but is not defined in the text. I don't know the full definition myself (it means ¹⁴C/¹²C variation in parts per thousand relative to a standard, I don't know what the standard is).
2. Using a ratio throughout (and making the read easier by using leading superscripts)
3. Replacing "level" with "activity". While correct, the term "activity" might confuse people and may be needlessly complex.
4. Leaving it as "level". Although it is slightly incorrect, it's easy to read.

If the delta notation is wanted, I can try and find the definition and stick it in but I don't want to change the readability of the article by inserting more complex nomenclature. Cheers,Rickert 21:31, 3 February 2006 (UTC)

I disagree. A "level" suggests a concentration to me, like moles per mole of air, moles per cubic metre, kg per kg of air or something of that ilk. For example the production rate of carbon-14 depends only on radiation and nitrogen, where the concentration of the latter, being the major component, is essentially constant. So were it not for the enormous rate of aquatic exchange (see the fast drop of the bomb peak) the concentration of carbon-14 would be nearly independant of that of carbon dioxide. So it is correct to say we never measure the concentration or level of carbon-14 in anything but only its ratio to total carbon or to carbon-12, which is just about the same thing. In many places there is no need to be strictly exact about that and e.g. "level" is, as you say, shorter and easier. But there are some where just this distinction is relevant, and in these it needs to be made.

One of those places is just this paragraph, which explains what exactly is measured and what is behind those raw laboratory values of some numbers bp. - Axel Berger 21:38, 3 February 2006 (UTC)

Hi Axel, thanks for the interesting response. You appear to be more well-versed in the vagarities of carbon dating than I. I don't quite understand what you were getting at (it is my ignorance, I am sure). Do you propose that the current nomenclature is correct or not? Perhaps I can help by clarifying what I mean by the possible equivalance of level and concentration.

If level means "mass of ¹⁴C per mass of air" it is incorrect because in this case the level/concentration will vary with total carbon abundance. For example, if I were to take two 1 kg samples of air in my office right now they would both have the same ¹⁴C mass, total C mass, ¹⁴C concentration and total C concentraion. Suppose I were to remove most of the N₂ and O₂ from sample 1. Both samples would still have the same ¹⁴C mass and total C mass, but they would have different concentrations of of both ¹⁴C and total C (the concentration of ¹⁴C has increased because, in this case, it is measured relative to a unit of air). Both aliquots, would retain identical carbon isotopic ratios. In the text of the article, the reference is to different carbon isotopic ratios, not "levels" as defined above.

If, however, level means "mass of ¹⁴C per mass of total C" it is correct. If this is the case, however, it should be clearly defined. An easier solution is to just use the ratio (or the delta notation).

Does this solve the problem? Please let me know if I misunderstand, as is so often the case. Cheers, Rickert 22:19, 3 February 2006 (UTC)

You have clarified just the point I was making. In most cases "level" is a short and easy term to use and best for making things legible. But it can have just that kind of ambiguity you have explained. So if and when the context makes it important to be precise about just that, it is necessary to state that not the absolute amount or concentration of carbon-14 is relevant but its ratio to all carbon. So contrary to Jclerman I think it is a good idea to use both terms depending on context.

As to the delta notation, while it does have its uses I think it confuses the lay reader, who comes here to get a concise and first explanation, more than it helps. As contrary to oxygen-18 it rarely used for carbon dating, I suggest leaving it and saving ourselves and the reader from the extra explanation.

Right, sorry. I misunderstood with whom you were disagreeing with, my apologies. I agree with you completely. Agreed, the delta notation may be confusing to the lay reader and should not be extensively used. Although it is used in the figure without explanation.Rickert 16:25, 4 February 2006 (UTC)

Activity, activity level, level, concentration, signal (of carbon-14): all have and are being used as synonyms in the literature. The choice depends on the history of which disciplines and methods were used to measure radiocarbon (physicists vs chemists, proportional counting vs accelerator masss spectrometry). Lay users, and interdiciplinary users of the web who use, e.g., atmospheric data, have no problems in understanding the meaning. By the way, the wikipedia definition of concentration doesn't apply. Feel free to put all definitions in an appendix to the article and to request to the person who inserted the graph to re-draw it using concentrations rather than the units reserved to the practice of stable environmental isotopes (C-13, O-18, N-15, etc.). And it would be useful and interesting to graph also the Northern Hemisphere data. The standard used is a sample representing atmospheric radiocarbon in 1950. It seems that the article failed to convey this idea. Jclerman 18:03, 4 February 2006 (UTC)

I understand where you are coming from, but as an encyclopedia article it should strive to use precise and accurate terminology wherever possible...sloppyness in the literature notwithstanding. Admittedly, when precision comes at the expense of, say, legibility (for example where a purely mathematical argument would be correct, but only a few people would understand it) sacrifices must be made. But where a slightly ambiguous term can be easily substituted for a much more precise one, with no cost to readability, I would suggest that the more precise one be used. But that is my final comment, others here seem to be more intimately familiar with carbon dating. Cheers, Rickert 19:07, 4 February 2006 (UTC)

Use of level

Both lay persons and scientists understand the use of the term level for all environmental variables, as exemplified by the use by both the BBC and Science journal. From today's news: << In November, Science published a paper showing atmospheric levels of the greenhouse gases carbon dioxide and methane are higher now than at any time in the past 650,000 years. >> Jclerman 21:02, 9 February 2006 (UTC)

Which is exactly my point, more or less. The level of 14C in the atmosphere is irrelevant - what happens when it stays constant while that of total carbon dioxide falls or rises? This may be nitpicking, and generally it is, but not in a paragraph strictly defining what exactly it is that's being measured. - Axel Berger 18:56, 10 February 2006 (UTC)

Would you find clearer to use abundance as NOAA [11] does? See their article and feel free to put the definition in an appendix to the article. I have requested to the person who inserted the graph to re-draw it using percent values rather than delta values. And it would also be useful and interesting to graph the Northern Hemisphere data. BTW the rise in total mass of carbon dioxide by admixture of CO2 from burning of fossil fuels has been taken care of, see the reference to Suess effect in the article about Hans Suess. Jclerman 19:25, 10 February 2006 (UTC)

level or abundance ?

Axel: I'm sure that, if you haven't visited them yet, you'd enjoy visiting and discussing all these topics with Herrn Dr Jurgen Freundlich and/or the other staff at a lab I think is not too far from you. See [12]. If you get in touch with them, please convey my greetings.

Jclerman 20:41, 10 February 2006 (UTC)

dating conflicts

Please:

• Propose in this page the examples you want to be considered.
• Include possible rebuttals and/or explanations already.published for each case in scientific publications (i.e., not in Newsweek).
• Do not include moon rocks and other samples not datable using radiocarbon.

Jclerman 06:09, 7 February 2006 (UTC)

The stuff about molluscs and moonrocks recently removed from this article has just been given its own article, Controversy on Radiometric dating, again with none of the counter-evidence. It is therefore completely POV. I remember reading that the snail shells were found to come from an ecosystem fed from ancient aquifer-water, but I don't know the source, and I'm not knowledgeable enough to un-POV the new article. Just letting people here know. --Squiddy | (squirt ink?) 14:10, 7 February 2006 (UTC)

I've seen the talkorigins answer on that very subject, it actually seems very plausible, but that aquifier water isn't the only thing those snails could of gotten C14 from, unless that water was like diluting most of the water shed and everything around it or something, which I don't think the talkorigins page mentioned. Personally, i'd like to see some of the examples on some of the more famous fossiles of Neanderthals since those are often the most famous things to have controversy over, the talkorigins archive had a very....interesting answer to conflicts on one of those I think, in which it claims that since bones are porous, of course the C14 dates would be all messed up as it would leech into it continually. Which of course begs the question how can any C14 dates of any bones be reliable, I understand how you can use dating methods on the land around it, but then all those other methods have to of been stable for thousands of years which is often very unlikely....but that's just my opinion, in the end, some more things on Neanderthal and other supposed human ancestor dating would be nice. Homestarmy 14:32, 7 February 2006 (UTC)

Risking to be rude, let me ask you whether you have read my response to you in this same page, above, here repeated: All your questions, critiques, and objections have been answered and discussed at length in the references given in the article. The detailed explanations given there are much more complete and thorough than we could do in this column. Also, if there is a radiocarbon dating lab in your locality, you probably could join an organized group visit and get a direct view and understanding of the method. In particular they could "walk you" through all the chemical and physical aspects of sample decontamination. analysis. computation, etc using data from real samples so you could compute yourself their ages and so get an "insider's view". Jclerman 01:22, 29 January 2006 (UTC)

Wha? No, I was earnestly suggesting this article contain some more things about it, you asked for ideas, I was giving one, and giving some background information on my opinion, but simply ended by re-iterating that I thought it would be a good thing to put into this article, as those kinds of examples are popular topics. You told me to go get some real reaserch on C14, so I went to talkorigins and looked stuff up, I don't know any carbon 14 labs near my area and I don't see why real information on C14 dating must only be in carbon 14 labs. Homestarmy 16:06, 7 February 2006 (UTC)

I do hope useful ideas and text are added. My suggestion to visit a lab is because I don't know what's your background and experience in the sciences and seeing the procedures and samples is equivalent to hundreds of pages that don't belong here. If you can get hold of a chemistry instructor of a high school or college: ask her/him to show you how to extract the mineral part from bones and shells, until the collagen matrix remains. Then the reply to your questions about bones and shells dating will click. Jclerman 20:17, 7 February 2006 (UTC)

Well we have a great chemistry teacher at a great private school but the problem is we don't have a great budget for a great chemistry lab, I think we might of blown most of the funds on silver(II) nitrate anyway :/. But are you saying talkorigins isn't the famed repository of evolutionary knowladge that people sure seem to make it out to be? I mean it seems like a very straightforward site with increadible detail, and the answers seemed very straightforward and earnest and it seems like it was worked on for a very long time, though they did give answers which seemed deceptively simple and short along with deceptively wrong to me at least.... Homestarmy 02:12, 8 February 2006 (UTC)

This topic is now being continued in Controversy on Radiometric dating and its corresponding discussion page.Jclerman 15:41, 7 February 2006 (UTC)

That page dose not exist now and I see no reason to create it. The discussion is doing just fine here. Lotu 23:35, 22 March 2006 (UTC)

Reliability

This article should also mention the questions of reliability of carbon dating. Until this is done, (I don't think I know enough about it to write it myself) I will be placing a NPOV dispute notice on the page. AH9 15:50, 11 March 2006 (UTC)

Reliability seems well covered in the sections Measurements and scales and Calibration. Or were you just referring to creationist objections based on religion? Removing tag. Vsmith 16:07, 11 March 2006 (UTC)

I was referring to the objections based on the fact that we don't have reliable carbon samples from as long ago as some objects are dated to compare the levels with. Replacing tag. AH9 16:14, 11 March 2006 (UTC)

I can't figure out what you are trying to say here. Can you please be a little more clear. Guettarda 16:15, 11 March 2006 (UTC)

Agreed. How about some refs on this. Radiocarbon dating has been verified by a variety of other dating methods (radiometric as well as others such as dendrochronology). Vsmith 16:30, 11 March 2006 (UTC)

Radiocarbon dating requires several assumptions.

1. We know how much Carbon-14 and Carbon-12 were in our original specimen.

True, if you mean before the specimen died or was taken off the exchange system

2. No Carbon-14 or Carbon-12 was added or lost during the time this fossil died to today.

False. We measure the decrease of C-14 in the sample to determine its age.

3. God had nothing to do with it.(This I believe is the majority view, but usually necessary to determine something to be really old.) I'm just curious. How does radiocarbon dating produce millions of years (e.g. dinosaurs) if Carbon-14 totally decays within about 50,000 years?

Off topic. Science is faith independent.

False. C-14 does NOT date dinosaurs.

True. The maximum C-14 age detectable is about 60,000 years.

And isn't coal (which has never been found without Carbon-14) supposed to have existed several hundred million years ago according to the Geologic Column?

False. If fossil coal was found with detectable C-14, it was due to contamination with modern organic matter, usually during sampling.

True. And again its age is NOT measurable with C-14.

Is there some place where we have found the whole Geologic Column complete and intact with all its index fossils?

See geology textbooks.

I am just curious if someone can enlighten me to the answers to these questions.Alisyd 16:19, 13 April 2006 (UTC)

Done. See above. Jclerman 16:58, 13 April 2006 (UTC)

I looked up how radiometric dating is done. Correct this is if I'm wrong. Carbon-14 decays into Nitrogen-14. In dead specimens, C-14 decays into N-14 halfway in about 5,730 years. So in about 11,460 years there should be 1/4 of the original amount. After 50,000 years C-14 is virtually impossible to detect. However the assumptions remain. 1. We know that there was no daughter material(N-14) in the original specimen.

It doesn't matter. It might have been, depending on the composition of the sample but we don't look for it in the sample to be dated. We only look at the C-14 activity or concentration.

2. Decay rates have always been the same.

Correct.

3. The system was closed and so no parent or daughter isotopes were lost or added.

Production rate and mixing rates have varied but are corrected by calibrating the scale (see the article).

Science is testable and observable. No was there when the object died so no one could know whether these assumptions are true or not.

There are datable materials (such as tree-rings) which recorded the events.

As for the geologic column in textbooks that is the only place on earth where one can find it. I have also heard that index fossils like Coelacanth have been found alive.

Then they were not fossils. Scientific observations are testable and verifiable. After the hypothesis are corrected, we progress towards a more correct knowledge.

Lastly, I noticed it was interesting that first you tell me C-14 is measured by its decay rate but if coal is found with it then it must have been contaminated. How do we know that these fossils haven't been contaminated? Alisyd 17:46, 14 April 2006 (UTC)

We know about the degree of contamination with admixture of modern carbon by cleaning physically and chemically. Progressively cleaner samples give radiocarbon ages which approach the real age.

Jclerman 18:54, 14 April 2006 (UTC)

What is being dated?

The BBC reported that the giant tortoise that recently died in India (Adwaitya) was going to be carbon-dated in order to determine its precise age. (This was reported by BBC-TV; the claim is not repeated in the on-line version of the BBC's report that is linked to from the Adwaitya article above). This sounds strange to me: I thought that what this method dates is the moment of death of a creature, not its moment of birth. The article does not seem to address this question. JanCeuleers 09:56, 25 March 2006 (UTC)

The BBC Online says, indeed, that: <<The shell of Adwaita, an Aldabra tortoise, will now be carbon-dated.>> It means the oldest parts of the shell Jclerman 10:20, 25 March 2006 (UTC)

And hello? thats why carbon dating measures the DECREASE of 14c if a fossil is tested and has zero 14c then what was it contaminated with?? Nothing? that means its at LEAST 50,000 years old as opposed to 6,000 which is most creationists beliefs.

Some conventions regarding radiocarbon results

(title revised)

• New section moved here due to internal and external inconsistencies, unexplained steps, and confusing typos and errors. Discuss here revised versions. Jclerman 07:13, 26 March 2006 (UTC)

Clerman and I are rewriting this so what you see is the version being progressively revised. Feel free to join the process if this would interest you.Dave 02:17, 28 March 2006 (UTC)

Opening of discussion

Hello Jclerman. I'm glad to see there is a watchdog on the article. I note your previous participation in that capacity. But, let me open by saying that I think the article needs more than just a watchdog. For the moment I'm interested mainly in calibration. The article doesn't really tell you what is going on in calibration. It has no mention of bristlecone pine or Irish oak, does not actually tell you in plain English what a calibration curve is or mention any international efforts to agree on a curve. It does not tell you what the formats of a calibrated date mean. A few vague generalities about calibration are all you get. Now, you can find SOME tutorials and expansions in the external links. I just thought this section ought to have more explanation and some pointers. I invite you or anyone to clean up the material below or provide a different write-up. If you do that, I will follow up on what YOU say (or anyone says). If not, why don't you begin by stating your philosophy if different? If we are going to clean up what I wrote below, then please state what internal and external inconsistencies you find, so we can fix it. Fair enough?Dave 12:18, 26 March 2006 (UTC)

Revised proposed addition

<< There are many conventions and techniques of deriving radiocarbon results. Once the results have been obtained, they must be stated in a way that is comprehensible to those who rely on them to date the historical (or prehistorical) phenomena in which they are interested. Archaeological and other publications therefore make use of a standard convention, which you may find explained in simple terms in the "Layman's Explanation..." web page linked under "External Links" below. It is being published by the University of Oxford Radiocarbon Accelerator Unit. This convention has varied somewhat historically, as is explained below. A brief summary follows.

A raw, or uncalibrated radiocarbon date is stated as years before present (BP). Seeing a BP date, the ordinary reader will immediately want to subtract 2000 years to obtain a date BC (or calculate the date AD); e.g., 9000 BP appears to be 7000 BC. For rough estimates in general reading and quick calculations of the dates of archaeological periods, which are very imprecise, this method is useful, provided the date is not a raw radiocarbon date. The latter needs to be calibrated to obtain the true date indicated by the results. In the example, 7000 BC is not calibrated and could be 10-15% in error.

Calibration can be as simple as a look-up on a graph of raw dates BP on the vertical, or y-axis, and calibrated (cal) dates BC or AD on the horizontal, or x-axis, such as the "calibration curve" shown above in this article. The term, calibration curve, refers primarily to the jagged line shown in the graph, and secondarily to the whole graph. One looks on the vertical axis to find the BP date to be converted, traces horizontally across to the calibration curve, and then traces vertically to the horizontal axis, where the calibrated date can be read.

This is supposed to be an encyclopedia, not a laboratory manual. It is our job to explain how and why published calibrated results can be ambiguous or far less precise than the raw laboratory value suggests to help users undestand them and interpret them correctly, but not to teach how to use a curve or software package. - Axel Berger 09:02, 30 March 2006 (UTC)

More typically, a computer program performs a virtual lookup using algorithms and data stored in the program and in memory. You enter the raw date through a field in the screen and the program displays or prints the calibrated date. The external links below point to sites, such as CalPal, where you can obtain a calibration.

The calibration curve itself is the result of decades of measurement and research. To obtain points on the curve, researchers took radiocarbon dates on samples whose dates were known by other methods, such as dendrochronology. Some very long-lived trees; e.g., California bristlecone pine, offer a continuous series of known dates over thousands of years. Once the points were known, the lines could be created by various methods, such as statistical curve-fitting (regression analysis). For such a span of years, it was necessary to use different methods for different sections of the graph.

All measurement is subject to some variability; that is, if you take several measurements of a quantity, they will be found to vary at random. Statistics characterizes this variation by calculating a mean value and a spread of deviations from this value, which are called "errors". You can then calculate a standard deviation (STD), represented by the mathematical quantity, σ.

---

end revised part of section

For purposIt has been called "the probabilistic approach.

es of calibration, the BC date is stated with a tolerance, such as 3450±50 years BP. This is not a mechanical tolerance, but a statistical one; that is, measurement took into consideration the variance due to a number of factors, including error, and a standard deviation (STD or σ) was calculated. In the example, the 3450 represents the mean and the 50 is the σ. In fact valid possible dates might exceed 3500 or be less than 3400.

A normal (random, Gaussian) distribution is now assumed, which is represented by a bell-shaped curve on a graph of numbers of standard deviations on the x-axis versus probability or frequency on the y-axis. In this kind of distribution, 68.26% of the dates or possible dates will be found within 1σ; that is, between 3400 and 3500. This is called the 62.26% confidence interval, because you are "62.26 confident" that a given date will be in this range. 95.46% of the dates are at 2σ; that is, the confidence limits are 3350-3550.

One now imposes the x-axis of the bell-shaped curve on the y-axis of a graph of calibrated dates BC (x-axis) versus raw dates BP (y-axis). On such a graph, the "calibration curve" is a line of plotted points, the coordinates of which are dates BC and BP. In contrast to the one shown above, the curve is typically quite irregular, bending up more than once so as to give two or more possible ranges of BC dates for a given range of BP dates. Also, the line is usually double, representing an error tolerance.

A confidence interval of BP dates translates to a confidence interval of BC dates. However, there will be more than one confidence interval of BC dates if the calibration curve allows more than one range. Typically the normal curve for BP dates is shown based on the y-axis, which develops into a curve of one or more peaks for BC dates on the x-axis.

A single radiocarbon date is fully stated therefore as in the following example:

3450±50 BP

68.26 probability (or confidence)

3650 (86%) 3750 BC

3825 (4%) 3875% BC

In this fictitious case, the range corresponding to 3400-3500 BP uncalibrated is either 3650-3750 BC cal. or 3825-3875 BC cal. The number in parenthesis states the probability associated with each range; that is, 86% of the dates will be found in the first range and 4% in the second. Sometimes fractions are used for percentages: .86, .04. One can estimate by picking the highest-frequency range and assuming that the others are error variations, or taking the whole range, peaks included.

Prior to this method, the intercept method of Pearson and Stuiver was commonly used; for example, Gimbutas used it in such publications as The Civilization of the Godess. In this method, the x-intercepts of the 1σ interval are taken as end points of a range stated, for example, in this format: 7050 (6771, 6742, 6716) 6568. The numbers in parentheses are the most probable dates of the peaks of the ranges present. This method fell out of use because it did not indicate any of the probabilities. >>