Carbon-14 Dating

Great Debates
1

I am not sure if I am allowed to do this, but I will try. I have been reading a lot lately, sparked by my reading in this Forum, trying to devour what I can about the Evolution Debates.

I would like to post an idea I have run across and get some comments. Here goes:

The idea is that Carbon-14 radiocarbon reading, which many anti-creationists use to shoot holes in the idea that the world is only 6000 years old, is not really as accurate as most people believe. The claim is that the process depends on the assumption that atmospheric concentration of radioactive C-14 has not changed since the Big Bang. Similarly, it requires that c-14’s rate of decay has not changed.

Evidence that these assumptions are erroneous:
[ul]
[li]Methuselah, a bristlecone pine tree in California is estimated to be 4,600 years old.[/li][li]A similar tree, believed to be older, was cut down for research.[/li][li]This second tree’s radiocarbon readings were compared with its growth rings.[/li][li]This comparison showed a discrepency.[/li][/ul]

The idea is that this discrepency demonstrates a fundamental flaw in the efficacy of C-14 radiocarbon dating: An organism could conceviably seem to be, by today’s assumptions of yesterday’s radioactive bombardment levels and rate of decay, thousands or millions of years old only months after its death.

Comments?

2

Well, let’s look at this.

The assumption that C14’s decay rate does not and has not changed: we base this assumption on what we know about nuclear physics now. There is no mechanism by which the stability of the C14 nucleus could be changed.

(A sidebar: changing our assumptions would mean rebuilding a lot of science from the ground up. You can’t do just one thing.)

Now, of course, a thousand well-reasoned theories are never comparable to a hard fact. If it could be shown that C14’s decay rate does change under certain circumstances, we’d just have to say, “Oh well, so much for current science” and start over (maybe we’d be able to save much of it by saying, “OK, it’s not exactly true, but under most circumstances it’s a pretty good approximation, like Newtonian mechanics is.”)

But, I don’t believe that there is evidence that C14’s decay rate has changed or can be changed.

Now, the criticism that the production of C14 has changed significantly has a little more room to stand in. C14 is produced by cosmic secondaries in the upper atmosphere from N14 (the by far more common stable isotope); it then decays back to N14. Now, N14 is obviously volatile; under most circumstances we cannot count on it’s lingering in once-living tissue for a ratio of C14/N14 to be detected. Instead, the actual amount of radiocarbon must be measured, which can leave room for error.

OTOH, the assumption that C14 production has changed enough to introduce serious error into dating is not one that can be satisfied by invoking minor changes in the irradiation of the Earth. We need (doing a BOTEC, which could easily be inaccurate) two or three orders of magnitude of increase in iradiation over the past few millennia to mess up C14 dating that much. Moreover, radioactive decays such as Rb87->Sr87 and the upper reaches of the uranium and thorium decays chains, which don’t involve volatile fractions, and don’t involve progenitors created by cosmic radiation, give ages of terrestrial rocks of millions and billions of years. Invoking a major change in irradiation could, in theory at least, mess up dating of recent prehistorical and quasihistorical times, but it’s not going to save “young earth” creationism.

Now looking at the specific points mentioned:
[ul]
[li]“Methuselah, a bristlecone pine tree in California is estimated to be 4,600 years old.” So?[/li][li]“A similar tree, believed to be older, was cut down for research.” OK, accepted (although I don’t know why it would be necesary to cut it down; neither dendrochronology nor carbon dating require it).[/li][li]“This second tree’s radiocarbon readings were compared with its growth rings.” and “This comparison showed a discrepency.” A question that immediately springs to mind is: how big a discrepancy? Radiocarbon dates are never given, to my knowledge, as “X years B.P” (before present), but “X ± Y years B.P.” (I suppose that some careless or unscrupulous person might have quoted the date as “X years B.P”, giving the impression of a precision that isn’t there).[/li][/ul]
Point #1 seems irrelevant, unless I’m missing something. Points #2 and #3 both differ enough from accepted practice that I require a little more evidence to show that someone did what is not ordinarily done.

3

Akatsukami:

Thank you for answering so clearly. As you can imagine, after spending a few weeks reading this stuff, I have begun to become confused - I’m not always able to catch an author skipping steps.

Your answer is cogent and helpful.

Thanks!
(Some Debate, huh?)

4

Furthermore…

This may be a nit, but neither the Earth and its atmosphere, nor any isotope of carbon were formed at the time of the Big Bang. At least one “solar generation”, lasting billions of years, had to be completed before enough higher elements existed to form rocky worlds, etc.

5

Sdimbert, here is some further reading if you’re interested:

This one deals in part with radiometric dating, also showing how it works in the grand scheme of things:

http://www.talkorigins.org/faqs/dating.html

Here’s one about isochron dating:

http://www.talkorigins.org/faqs/isochron-dating.html

A general one on the age of the Earth and how scientists have figured it out:

http://www.talkorigins.org/faqs/faq-age-of-earth.html

From those, you can navigate around and see if there are any others that interest you.

6

A couple more comments:

Carbon dating in things as young as a living tree is not terribly reliable. Statistical variation will mess things up somewhat.

Also, I once heard of a study (sorry, no cite. I know) where they took many samples of old wood found in the same general area. They looked at the pattern of rings (i.e., small rings in dry years and bigger ones in wet ones), and using these, were able to find overlaps in the different samples and put together a chain going back a long long time. In this way, they were able to directly examine the level of C14 in the atmosphere. They found that its level has fluctuated over time, and has increased in recent years. IIRC, they found it was increasing very slightly until the Industrial Revolution, at which point it began increasing much more quickly.
The point is, C14 levels have changed over time - a little. Most radiocarbon dating these days now takes this into account, and corrects for our best guess as to what the level would have been then. Hope that helps somewhat.
I’m working through the aftereffects of 2 Excedrin washed down with a Mountain Dew, so I’m kind of incoherent right now. Even more than usual.

7

Do I miss something here? I always thought that radiocarbon dating was used to determine the age of DEAD tissue, ie to find out how long ago a tree was felled etc, and given that, why on earth would anyone use it on a living tree?

Floater

8

Thank you all - good information and thoughtful answers.

DavidB - as usual, you’ve exceeded my expectations. Thanks for the cites… I’ve checked two out and expect to have some more time later today.

Was I right to be apprehensive about the format of my OP? Or is it OK if I try that trick again? I read a lot and don’t always understand what I’m reading… Is this Forum an appropriate place to come for clarification, comments and a healthy dose of re-thinking?

9

Most C 14 dates are corrected for known/postulated variations in the amount of C 14 in the atmosphere. The data for the correction involves many iterations of known dated organic materials and raw C 14 dates. The result is sort of a saw toothed graph showing probable amounts of atmospheric C 14 through the last 20K years. The thing that I find fascinating about this graph is that it MIGHT be showing variations in the earth’s magnetic field. As mentioned by Akat, the C 14 is produced by N 14 and cosmic radiation/particles. A variation in the earth’s magnetic field, would allow less/more charged particles and produce less/more C 14 like the graph shows. I am really concerned about magnetic reversals and am desperately looking for such a precursor since I sunburn easily.

10

IIRC, Carbon 14 has a relatively short half-life (on the order of a few thousand years) and isn’t used much in the geological dating that evolutionary theory depends on. Generally geologists use radioactive materials with much longer half-lives like some Uranium isotopes. Since these are buried deep within the earth, it’s a safe bet that there “relative abundance” hasn’t changed.

essentially geologists use a three pronged approach to dating rocks: Radioactive decay, the fossil record, and classical geology. By using these methods to cross check each other, extremely accurate datings can be obtained.

11

That’s probably true. However, that is not to say that it is not as accurate as scientists believe.

No, there’s no way that could happen, because:

  1. This would require an extremely low C-14 level, by several orders of magnitude (and C-14 dating doesn’t really deal with things million years old).
  2. If C-14 levels were that low any time in recent history, scientists would have noticed.
  3. If one month old sample is dated as thousands of years old, then all month old samples would be so dated. Scientists would have noticed such a thing.

If you were just looking for a clarification, GQ might have been a better place for this question. If you want to keep this thread in GD, you should respond to responses more beligerently and constantly contradict what other people say. An occasional insult might help, too. All this politeness is so… out of place.

12

Ah, but sdimbert is a poster looking for contradictions to answer him (her); not for answers for him (her) to contradict!

13

SDIM: C14 is not used to measure the age of the Earth. It only goes back so far, and besides, the Earth was around for billions of years before Life. All the evidence, not just C14, points to the Earth being 10000X older than 6000 years.
And the evidence that the Universe is at least 13 billion years old, hardly comes from C14. Even without C14, ther is plenty of proof of the (rough) age of the Earth & various forms of life.

But, thanks for being such a nice guy on this.

Incidentally, the 4000BC figure for the Earth is not a bad figure for the begining of civilization. However, Jericho, prob the 1st city. was around in 8000BC.

14

The Ryan said:

No you shouldn’t!

15

Oh, and SDIM, Beer was invented at least 8000 years ago. Who drank it for those 1st 2000 years? :smiley:

16

In 1972, in Uppsala, Sweden, there was an international convention of scientists; suffice it to say that they tested several hypotheses regarding the radiocarbon clock and found, among other things, that 1) The half-life of Carbon-14 is not 5,568 years; and 2) The rate of decay of the radioactive isotope has not been consistent (that is, even) in the last 5,568 years, or whatever period.

17

Of course the half-line isn’t 5,568 years; it’s 5,730 years.

As for the rest: no cite given, the one fact given is given wrong, and the convention was apparently so poorly publicized that, twenty-eight, it is still ignored worldwide. Sounds like another creationist lie to me.

18

The rate of decay is consistent, the amount of C14 in the atmosphere has not been consistent. However, the correction has been calibrated.

19

Gosh, when it comes to science, I always try to just take the word of a guy who’s willing to kill children in order to support his particular interpretation of the Bible. So if dougie_monty says there was a conference, and gives no other information whatsoever, well then, I’ll just believe it and pack up my scientific bags.

“The most amusing threads on this board involve David B kicking some obnoxious creation scientist ass.” – Greyson3

20

I can’t find any references, even in the on-line creationist literature, to any such conference in Uppsala.

The closest I can find is something that appears in many pro-creationist places, including Radiometric Dating Game:

“Dr. Libby, the discoverer of the C14 method, which won for him a Nobel prize, expressed his shock that human artifacts extended back only 5000 years, a finding totally in conflict with any evolutionary concept. Older dates were found to be very unreliable (CRSQ , 1972, 9:3, p.157). By this time tens of thousands of C14 dates have been published from tests performed by various laboratories around the world. In the annual volumes in which the dates are published, concerns have been expressed about many relatively young dates that violate established geological age notions. One example given was Ice-Age materials that were dated by C14 to fall within the Christian era (CRSQ , 1969, 6:2, p.114). In his book on prehistoric America, Ceram notes a classic case of the difficulties that befall C14 dating. Bones 30,000 years old were found lying above wood dated at 16,000 years (Ceram, 1971, p.257-259). … Even more astonishing is this cynical statement made at a symposium of Nobel Prize winners in Uppsala, Sweden, in 1969: If a C14 date supports our theories, we put it in the main text. If it does not entirely contradict them, we put it in a footnote. And if it is completely ‘out of date,’ we just drop it (Pensee , Winter 1973, p.44).”

Note that there’s no mention of who allegedly made this statement, just where it was allegedly stated.

I attempted to look up some of the references. It’s a little difficult because the author does not, as should be standard, list where to find his sources … perhaps it’s reasonable to assume that, in the closed and closed-minded society of “creation science”, everybody knows? All the ones I located were creationist literature, with the exception of Pensee … that’s a Velikovskian “journal”. None of the articles are online, but some abstracts are, and can’t see any indication in the abstratcts that any or these references might be true …

PENSÉE Volume 3, Number 1. Winter, 1973 contents

Creation Research Society Quarterly Volume 6, Number 2 Abstracts

Creation Research Society Quarterly Volume 9, Number 3 Abstracs