Talk:Radiometric dating

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Radiometric dating a myth?[edit]

The following discussion has been closed. Please do not modify it.

Yes i think so. The fact that someone can take a stone arrowhead and date it back to the time when it was carved, not when the rock itself was created is just insane. The piece of flint that the ancient man found and carved into that arrowhead was already there hundreds of thousands of years before. The only possible date you can get from that stone would be the date that the radioactive element that is being tested for was created (aka the beginning of the universe when all elements were created). Carbon-14 (C-14) is a radioactive element that is taken into our body over the course of your life at the same ratio as carbon-12, but that means it existed outside of your body before, (thousands of years before). C-14 is the element used to date fossils and other organic materials, but if the C-14 atom existed before then how does it just know to start decaying when the organism dies? The only place in the universe that we know creates elements is inside suns (fusion) and all that is happening is fusing hydrogen to create helium. How hard is it to create uranium by fusion (fusing over 200 protons, the sun only compresses two). So thinking of this how can it work it just doesn't make sense. Wouldn't radiometric dating be best described as a myth that just gives ordinary people some reason to believe scientists when they say how old something is? Just something to think about, and i may not know all the in's and out's of the process so please inform me if you do. (talk) 05:07, 11 December 2007 (UTC)FMorris

Apparently you have not read the article! Carbon-14 is being continuously generated in the atmosphere by cosmic-ray bombardment of Nitrogen-14. Living things take in CO2, then stop doing so when they die: this can be used to date wood, bone etc. Rocks are dated from when they solidify (using other elements): the products of radioactive decay then begin to accumulate within the crystal structure. Neither method can date the carving of stone. --Robert Stevens (talk) 10:04, 11 December 2007 (UTC)
It is interesting to note, that by the method of Carbon 14 dating, the oldest known organic substance, coal, cannot be dated older that about 45,000 years. At 50,000 all remaining C14 is undetectable. For years scientists have been looking for a sample of Coal with "zero" C14 to use as instrument calibration. Unable to find even one such sample, they have given up. C14 dating has shown not that organic material is older than 50,000 years, but rather that there is not one example of any organic material found on earth that is older than about 45,000 years.
Radiometric Isotope dating has been a poor replacement for C14, as they have repeatedly found it to be sporadic, and unreliable. For example, volcanic flows of known age (less than a few hundred years old) have repeatedly shown ages far older than they should. Not small errors, but errors in millions of years. Radiometric dating is unacceptable as scientific proof of anything other then our weakness when it comes to radiometric dating.BreshiBaraElohim (talk) 01:37, 18 October 2008 (UTC)

I hope that dude was joking... —Preceding unsigned comment added by Shniken1 (talkcontribs) 12:28, 11 December 2007 (UTC)
I actually saw a program where a stone arrowhead carving was supposedly dated using this method, they were trying to prove the existence of man on the north american continent before previously thought. Now that does sound like a problem and that is what made me write this up. I didn't ever say that i was an expert just some things about it just don't seem to make sense. Thanks for the input. (talk) 18:14, 11 December 2007 (UTC)FMorris

Most likely the arrowhead was dated using something like charcoal found in the same layer where the arrowhead itself was found. Mikenorton (talk) 18:55, 11 December 2007 (UTC)

"Stone arrowheads" can not be dated radiometrically. Radiometric dating requires an isotopic "reset" to take place, that is to say, something happening to the material that would change its isotopic composition to a calculable ratio, and block further matter transfer with the outside world. For many minerals, it means either sedimentation or solidification, but rock carving techniques are insufficient. Carbon dating can be applied on organic material, provided the non-contamination conditions are met, but a "stone arrowhead" is not organic.

Generally, of artefacts, only wooden artefacts can be dated directly - either by carbon dating or dendrochronology. Other kinds of artefacts can only be dated indirectly, usually from the context of their finds. For example, it may be possible to find arrowheads together with dateable pollen, or tied to wooden arrowstalks, or next to people of a distinct culture whose appearance and disappearance times are known.

If your movie claimed that the arrowheads were radiometrically dated, it's junk. Could be creationist, could be ancient astronaut, I don't care: it's pseudoscientific junk. —Preceding unsigned comment added by (talk) 15:27, 14 June 2008 (UTC)

I don't pretend any expertise in this area but could they have been talking about Fission track dating? According to that article the clock is reset as low as 70 to 120 °C for some minerals, which would occur in a camp or forest fire. Pterre (talk) 11:07, 13 September 2008 (UTC)

actually, radionmetric dating is based on the assumption that radioactive material decays at a steady rate. the dating is often performed on meteor, which is based on the assumption that the meteor is the same age as the earth. why isn't this metioned in the article?Ref ward (talk) 18:45, 5 March 2010 (UTC)

Sorry, could you run that by again? Dating of a meteor is based on the assumption that the meteor is the same age as the earth? So if you're assuming it's the same age as the earth, why would you bother to date it? Pterre (talk) 23:24, 5 March 2010 (UTC)

because dating a meteor is more "accurate", with no weather or atmosphere to interfere with the decay of the radioactive materials. the scientists believe that the meteors that often fall to earth are from the earth, due to a collsion causing the earth fragment to fly off into the atmosphere.Ref ward (talk) 17:46, 8 March 2010 (UTC)

<Do you have a reference for that?! It would be pretty obvious to a geologist if a meteor was originally from Earth. Such a thing has never been found.> Ezkerraldean (talk) 19:05, 10 September 2010 (UTC)

There are several different issues here:

  1. Isotopic ratios in meteorites (e.g. chondritic uniform reservoir) are used to model the age at which a sample is thought to have been separated from the mantle. This is not the same as the (crystallisation) age of the rock.
  2. Meteorites are often dated to try to determine the age of the solar system. This is an application of radiometric dating and not an assumption of the technique.
  3. Meteorites are widely used in isotope geochemistry to study the evolution of the mantle and of igneous rocks. This is more of isotope geochemistry than dating. Babakathy (talk) 08:39, 9 March 2010 (UTC)

Odd wording[edit]

After an organism has been dead for 60,000 years, so little carbon-14 is left in it that accurate dating has not been established. I see someone changed this to say "...that accurate dating cannot be established," which was reverted. Is the intent of the sentence as it stands to say that an "accurate dating method has not been established" for materials of greater age? Otherwise, I'm not sure why "cannot be established" wouldn't be a clearer wording. Agathman (talk) 14:38, 28 April 2009 (UTC)

Reworded some time ago, I guess. Babakathy (talk) 08:40, 9 March 2010 (UTC)

dating rocks younger than a few million years[edit]

I made a table of the isotopes mentioned in this article. Would it be helpful to include it? It would be even nicer if we had authoritative sources for the useful range of dating by each isotope system. But what sticks out when I look at the table is that most of the half-lives are in the billion-year-plus range. Radiocarbon and U-Th are less, but apply to rather special systems and even there cannot be useful beyond perhaps 1 million years. Is there a standard way to date rocks that are only a few million years old, or even younger? --Art Carlson (talk) 09:00, 14 September 2010 (UTC)

Some isotopes used in dating
parent daughter half-life
147Sm 143Nd 106 billion years
87Rb 87Sr 50 billion years
238U 206Pb 4.47 billion years
40K 40Ar 1.3 billion years
235U 207Pb 704 million years
234U 230Th 80,000 years
235U 231Pa 34,300 years
14C 14N 5730 years
3H 3He 12.3 years

Duh! Any isotope with a shorter half-life will have decayed away to nothing since the Earth was formed. Still, what do geologists interested in formations of intermediate age do? And is there anything equivalent to the cosmic distance ladder by which the billion-year methods can ultimately be connected to historical time? (Not that the first principles of radioactive decay are unsound, or that the cross-checks using a variety of methods are not convincing support. I'd just like to know where the limits are.) --Art Carlson (talk) 09:55, 14 September 2010 (UTC)

Conflict with young-earth creationism?[edit]

I would like to suggest adding a section on the conflict between young Earth Creationism and radiometric dating. It would NOT be an argument of the scientific merits of the two positions, as there doesn't seem to be any for the former. However, I do think it would be interesting and valuable to at least acknowledge that radiometric dating is one of the great supports of scientific understanding of the universe, and that it is denied by a faith-based class of people.

Beyond that, I would like to know just how young Earth Creationists attempt to dismiss radiometric dating. I'm sure there are a number of plausible-sounding objections that would take some thinking to refute, just as I'm sure that someone's taken the time to refute each one.

(Apologies if this has already been discussed; the archives seem to have a lot of arguing about whether radiometric dating works, but never talks about what I suggest above.) -- Dan Griscom (talk) 12:36, 1 May 2011 (UTC)

Extreme fringe views are not notable on an article on a scientific subject. If the views of the religious are notable at all they should be discussed in the article about the young earthers. Vsmith (talk) 14:01, 1 May 2011 (UTC)
The scientific refutation of creationist views on the subject is discussed at Creation Science#Radiometric dating. I agree with Vsmith that it does not belong in this article. Dirac66 (talk) 14:33, 1 May 2011 (UTC)

They're a fringe pseudo-scientific belief. They don't need to be mentioned in the articles covering the real science. That gives them undue weight. We have other articles specifically dealing with them. --Harizotoh9 (talk) 13:04, 5 April 2012 (UTC)

Error in the first equation?[edit]

I believe the age equation is wrong. It shows D growing exponentially without bound as t goes to infinity. I believe the correct equation should be:

D = D0 + N0(1-e-λt)

Michael Schmitt (talk) 23:58, 5 June 2011 (UTC)

Actually both are correct. The equation in the article is obtained by replacing N0 = Ne+λt into your equation to obtain:
D = D0 + Ne+λt(1-e-λt) = D0 + N(e+λt-1)
This does not increase to ∞ because N is not a constant. It may seem more mathematically transparent to use the first form in terms of the constant N0, but geochemistry references (such as the one cited by White) tend to use the second form because N is the measured quantity.
However this is the second time I have had to correct this error (see edits 21 Feb 2011) so perhaps the point needs to be made more transparently. I will replace N by N(t) and add an extra explanatory sentence. Dirac66 (talk) 02:46, 6 June 2011 (UTC)

Picture of mass spectrometer[edit]

If I'm not mistaken, the mass spec currently shown, a Thermo DeltaPlus, is used for stable isotopes? Maybe an ICPMS, a TIMS or an argon noble gas mass spec would be more accurate? Cheers — Preceding unsigned comment added by (talk) 14:59, 13 March 2012 (UTC)

No Discussion of Lava?[edit]

A core part of the logic behind radiometric dating is what is happening as the lava is cooling. I don't see any discussion of that in the article. Is the isotope floating about in the air and getting trapped in the lava? Are the parent/daughter concentrations different in the lava from the concentrations in the air? What are the relevant interactions between the lava, the cooled rock and the air? It seems this is yet another scientific Wikipedia article that assumes too much on the part of the reader, that sacrifices satisfying the general public to satisfying the experts. Br77rino (talk) 21:01, 2 April 2012 (UTC)

Lavas (and other igneous rocks) are dated from the minerals that are found inside them and date the cooling of the rock. Lavas are not dated by radiocarbon dating and so don't involve interaction with the air. This article could probably do with a section on the practicalities of dating different types of material - different methods are used for different things. Mikenorton (talk) 23:02, 2 April 2012 (UTC)
First of all, which isotopes are we discussing? Br77rino's question seems more pertinent to K-Ar dating, which does determine the date at which igneous rocks solidified from lava. Before we go any further, could Br77rino please confirm whether s/he was referring to K-Ar, C-14, or some other method? Dirac66 (talk) 00:21, 3 April 2012 (UTC)
I can't help thinking Br77rino might be a little confused - I don't see what air has to do with anything. Perhaps it needs explaining more clearly that both parent and daughter isotopes originate and remain within the rock which is to be dated? Pterre (talk) 08:29, 3 April 2012 (UTC)
For K-Ar dating, the simplest model is indeed that all parent (40K) and daughter (40Ar) isotopes originate in the rock and remain there once the rock has solidified. However this is not always strictly true and there can be a problem of contamination from atmospheric argon. See K-Ar dating#Assumptions for more details. Dirac66 (talk) 13:52, 3 April 2012 (UTC)
OK, but you are assuming that Br77rino is specifically refering to K-Ar, which s/he does not mention. I think a more general 'layman's terms' explanation could be added. Pterre (talk) 17:47, 5 April 2012 (UTC)


It would be helpful to qualify some of the assumptions required for different types of radiometric dating. While a few of the sections make mention, what about adding an 'Assumptions' heading? Major assumptions must be made, with the first being that we know the approximate levels of isotopes when the rock was created, and the second being that the levels of breakdown or radioactive decay have been consistent over time. As an ancillary assumption, we must also presume that no isotopes were lost or gained between the formation of the rock or material and the time of measurement. It presumes a constant level of energy and a relatively consistent environment to make these predictions. A variety of events may change the results, where something like even a major flood, changes in geologic and/or volcanic conditions, or a large solar flare on the sun might impact the calculation, let alone a super nova explosion, meteor, or other unknown cosmic event. For example, the frequency of supernova throughout the universe is estimated to be much higher than recently shown in our Milky Way, whereas such an event within about 100 Ma may impact isotopic values. — Preceding unsigned comment added by Sunny monday (talkcontribs) 01:06, 25 December 2013 (UTC)

Please read the section on preconditions which deals with the matter or parent/daughter isotope ratios and nuclide loss, and the age equation section on that matter and on initial compositions.Babakathy (talk) 08:23, 2 January 2014 (UTC)

Isochron diagram[edit]

The isochron figure has several errors and is long overdue for correction, so I'm just letting everyone know that I and my graduate students are going to fix this in the near future.Radiogenic (talk) 17:17, 23 September 2014 (UTC)

Radiocarbon errors[edit]


A sentence was added by Romanfall earlier today and later removed by Mikenorton about errors in the radiocarbon method due to bomb testing and burning of fossil fuels. I will add some further justification for the removal: this point is already covered in the article - see the third paragraph of the section Radiocarbon dating method, and in more detail the article on Radiocarbon dating. These discussions also make clear that these errors only affect samples whose age is recent: post-1945 for bomb testing and post-1750 or so for fossil fuels. The dating of older samples is not affected. Dirac66 (talk) 20:55, 15 April 2015 (UTC)

Something I'd like cleared up[edit]

Recently read somewhere that there's a flaw in the radiometric dating method, that we can't be certain whether the decay products of the sample in question are really in situ, or whether some of them were added from external sources after the sample was originally formed. I'm not a young-earth creationist and have generally considered radiometric dating to be a trustworthy scientific means of determining the age of rock samples, and as such I'm quite curious as to whether this "flaw" is in fact reliable information.-- (talk) 00:09, 2 May 2016 (UTC)

It would be helpful to have a verifiable source for this claim about sample contamination. My non-expert suspicion is that it may be true for certain isotopes in certain samples, but not in general. So it would be something to verify for any given sample, but in most cases contamination is not suspected. Dirac66 (talk) 00:56, 2 May 2016 (UTC)
Unfortunately I don't have a reliable source on hand, just a one-off comment from a mining geologist on Facebook whom I can't verify the actual credits of. Chances are it was hokum, but as a scientifically-minded individual I was just curious. Thanks for the reply.-- (talk) 13:20, 2 May 2016 (UTC)
I'm a nuclear/particle physicist, although I haven't worked on dating. But I would expect that contamination with the same radionuclide from a more recent era could be the most challenging aspect of some dating applications. In such cases, published articles reporting the results would address the issue, explaining how contamination was avoided in that work, and this information would be subject to careful scrutiny by peers. Correspondingly, the techniques developed to control contamination may be among the most important skills in the "trade". Layzeeboi (talk) 03:16, 22 February 2017 (UTC)


Hello! Radiometric Dating is a tool used for data analysis, the assumptions are on the halftime of the electrons of the elements been used to date the item being dated. Strength is that it can narrow the time down, the weaknesses is it cannot give the exact year but a proximation of decade or millennium. The text is a proxy of time done by calculations. The article is general easy to read.

Is there a more current article pertaining to Radiometric dating? The OSU list 38 articles after 2012. For example: . But there is a list giving further reading with activate links that take the reader to the ISBN page, while the DOI on the reference do take you to online article links.--Racer.12osu (talk) 22:31, 20 February 2017 (UTC)

Article Evaluation of Radiometric dating[edit]

This article explains very well on how we can use radiometric dating to learn more about climate in the past. We are capable of using carbon to find out the age of certain things, which allows us to find materials and such from thousands of years ago. This is an efficient method that scientists use today. It also explains the limits of radiometric dating since carbon-14 half-life can allow us to go so far back.

There were numerous peer-reviewed articles on radiometric dating. Some of them were used with in the article while there were several that have yet to be used within the article.

Recommendations: The only recommendation that I have is to combine some of the different methods under one section would be more beneficial since most of the sections are only one to two sentences long. The rest of the article goes into great details on how it works and shows plenty of images of the atoms and charts of the carbons half-life.

Adams.1714 (talk) 01:46, 2 March 2017 (UTC) Ethan Adams