Talk:Radiocarbon dating/Archive 2

message: * 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.
* 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  and here .
--Jclerman 01:39, 11 July 2006 (UTC)
thread_title:  About calibration 

message: : 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)
thread_title:  Constant cosmic ray flux assumption 

message: 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)
replies: text: 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)
replies: text: 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)
replies: text: 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)
thread_title:  Calibration curves as basis for dating 

message: 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)
thread_title:  Standard deviation 

message: 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)
replies: text: 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)
replies: text: 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)

text: 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)
replies: text:  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)

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

message: 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)
replies: text: 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)
thread_title:  Basics 

message: # 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.
# 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)
thread_title: Insider information 

message: 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)
replies: text: 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)

text: 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)

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

text: 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)
thread_title:  Earth's Magnetic Field Decay 

message: <B>ATTN: Cyoub</B>
*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)
thread_title:  Cyoub said: Obvious mathematical error. Show your work. 

message: 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)
thread_title:  Total rework 

message: 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.
 [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)
thread_title:  The role of Hessel de Vries 

message: 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)
replies: text: 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)
replies: text: Would you find clearer to use abundance as NOAA   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)
thread_title:  Use of '''level''' 

message: 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 . If you get in touch with them, please convey my greetings.
Jclerman 20:41, 10 February 2006 (UTC)
thread_title:  level or abundance ? 

message: 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)
replies: text: 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)
replies: text: 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)
replies: text:  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)
replies: text: 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)
replies: text: 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)

text: 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)

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

message: 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)
replies: text: 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)
thread_title:  What is being dated? 

message: 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)
thread_title: Opening of discussion