Talk:Radiometric dating

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Archive 1

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[edit] Sr -- Sm

The list of radiometric dating techniques at the end of the article includes

  1. samarium-neodymium (Sr/Nd)
  2. samarium-yttrium (Sr/Y)

Both items begin with samarium (Sm), but the chemical symbol shown is that of strontium (Sr) instead of samarium. I'd fix it, but I don't know what was intended. Mike Sarles

Fixed that (one was a duplicate) and removed the following for clarification and/or verification:
  • strontium-neodymium-hafnium-lead (Sr-Nd-Hf-Pb)
if it's real it can be put back. Vsmith 18:25, 27 August 2006 (UTC)
These are ratios used in isotope dating of mantle plumes: "Popular with plume enthusiasts is the ratio of helium-3 to helium-4. A higher ratio is characteristic of deep mantle origin, they argue. Similar information can be gleaned from isotopes of the elements neodymium, strontium, lead, and hafnium. The ratio of 3He/4He increases over time as 4He is produced by the decay of uranium and thorium. The present day atmospheric 3He/4He ratio is 1.39x10-6, and is referred to as RA. Geochemists infer deep origins whenever 3He/4He are in excess of 9 to 10 RA. These ratios have been found at hot spot locations such as Hawaii, and are consistently different than the basalts of the mid-ocean ridges....A better interpretation would be that the high 3He/4He ratio arises from a deficiency in 4He in the upper mantle caused by low U+Th areas, and thus low rate of addition of radiogenic 4He." http://www.emporia.edu/earthsci/student/sedlacek2/mantle.htm It's also referred to in the book "Radioactive and Stable Isotope Geology" by Hans-Gunter Attendorn and Robert N.C. Bowen. Valich 00:18, 12 February 2007 (UTC)

[edit] "Radiometric" dating?

The section "Short-range dating techniques" in this article contain interesting descriptions concerning various dating methods such as dendrochronology, "varve analysis", "hydration dating" or "obsidian dating", and thermoluminescence.

Strictly speaking, however, those methods do not belong to the topic of Radiometric dating, the current title of this article. Therefore, in my opinion, one of three things should be done: (1) rewrite the section so as not to appear as overtly off-topic; (2) move those other techniques to their proper places and place a link in "See also" section; or (3) rename the article to reflect a more general topic such as "Dating techniques" or the like. What do others think about this? --HYC 21:32, 8 September 2006 (UTC)

Moved three paragraphs to Incremental dating, which was a stub needing more info. Vsmith 22:17, 8 September 2006 (UTC)

Sorry. My fault. I thought U/U, Sr/Nd, Sr-Nd-Pb were radiometric datings but on further research I see they are isotope ratios. Valich 21:15, 10 September 2006 (UTC)


[edit] Re: illogical: Supervening influences on half life of samples

I understand that the half-life of a radio-isotope is unaffected by temperature, pressure, etc. But don't other radiological sources have an effect? e.g. the atomic fallout from a meteorite or a supernova in a nearby star system. It seems such events could trigger substantial 'non-spontaneous' decay that would cause is discontinuity in the typical half-life curve and set dates off by an order of magnitude. Also the level of C-14 in the atmosphere could increase significantly in response to such events too: making a sample appear younger than it really is.

No? Are there any reliable sources research on this? Shortopinions 20:00, 29 March 2007 (UTC)

Go to talk/radiocarbon dating, make a "history" and read last week's comments. Jclerman 21:00, 29 March 2007 (UTC)

[edit] Same animal dates

Living things have been dated over 2500 years old. so the procedure is not fact. Also different parts of animals have been dated. Example some part is 20000 years old and other is 35000 years in same animal. Posted unsigned, at 06:01, on April 22, 2007 by User:84.249.188.213 (Talk) (5,028 bytes).

Cite the reference and we'll tell you what's wrong. Jclerman 13:43, 22 April 2007 (UTC)
IIRC, that was a creationist lie invented by Kent Hovind. --Robert Stevens (talk) 09:38, 3 January 2008 (UTC)
The procedure is inaccurate either way, since in order to use radiometric dating you have to make an assumption about how many isotopes were in the object being dated, don't you? ex: I'm dating a T-rex, and I find - I don't know - twenty billion isotopes. In order to know how old the rex is based on that data, I'd have to assume that it had a certain number of isotopes from the start. So if the isotopes had a half-life of fifty years, I could assume it started off with 80 billion isotopes and say it's a hundred and fifty years old. Please correct me if I'm wrong. Zillakilla (talk) 01:21, 3 January 2008 (UTC)
Um, yes, you're wrong. Each type of radiometric dating uses the radioactive decay of only one isotope of one element. We know how much of the isotope was present originally by several means: such as measuring the quantity of decay product, in cases where the decay product could not have been originally present (e.g. potassium/argon: argon is a gas, therefore it can't accumulate inside solid crystals except by radioactive decay of potassium-40 in those crystals). --Robert Stevens (talk) 09:38, 3 January 2008 (UTC)
I'm not trying to be obtuse and perhaps this isn't the place for such a discussion, but I don't really understand how, excepting cases like Argon, one could determine how much of the daughter element was present when the decay started. The procedure seems simple enough, but you would sort of need to know that to get an accurate ratio? J. David Sargent (talk) 19:54, 16 March 2008 (UTC)

[edit] Radiometric dating a myth?

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.

70.125.94.59 (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)
I hope that dude was joking... —Preceding unsigned comment added by Shniken1 (talk • contribs) 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.

70.125.94.59 (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)