Radiometric Dating and Estimated Dates— A Scientist Responds
This article is a followup to an exchange I had with “Douglas” in the comments section of my recent posting, The Three Arguments Against Atheism. In that discussion, I offered to refer the question of estimated dates in radiometric dating to an actual scientist and post the result. The scientist I contacted was Dr. Daniel J. Berger, Professor of Chemistry at Bluffton University, Ohio. With his permission, I have published our exchange below.
From: Robert McNally
Sent: Sunday, December 31, 2006 11:46 PM
To: Daniel Berger
Subject: Question on Radiometric Dating
Dr. Berger,
I found your contact information through madsci.org, where I see you answered a similar question to the one I have. I hope you will take the time to clear up an issue that has arisen in an on-line discussion I am having with a young-earth creationist. This gentleman seems to presume that the Earth is less than 12,000 years old, and is therefore skeptical of radiometric dating methods, saying:
As for any of the “dating” methods - On the form used to submit samples for dating, is a space to indicate how old you “think” the sample should be. If this is an objective and reliable method, why is this field there?
Not being an expert in this area, I asked him to produce such forms, which he did:
Some radiometric dating submission forms for you:
http://www.brocku.ca/earthsciences/radiocarbon/
Check the link to the RTF request form on the left. Once you have the file, look for the “probable age” field.
http://www.radiocarbondating.com/submission%20form%202003.pdf
Again look for “Estimate Age” and “age limits” fields on this form.
http://www.gla.ac.uk/centres/surrc/radiocarbon/submission.html
Download the submission form in Word format. Also has the “estimated age” field.
These are just the first 3 forms I found using Google. All 3 ask for an Estimated Age. The last one even supplies some reasons - “this helps the laboratory to select the appropriate instrument for measurement as well as enabling the laboratory to contact the submitter at an early stage if the estimated age is excessively different from the measured age”.
I am sorry but the reasoning to justify this is very weak. I thought the whole point of radiometric dating is that it is supposed to objectively and reliably supply the dates based on radioactive decay rates etc. I think its nuts that you are submitting a sample to “scientifically” determine the age, and at the same time you have to give them your estimate and upper and lower age limits. What if I have a sample and I’ve guessed wrong by several billion years? They are using my guess to calibrate the machines, and the result comes back way outside of my limits. “Oops,” they say, “the machines must have it wrong. Lets repeat the process.”
As for contaminants, if these cannot be reliably detected by the dating lab, how can the process be considered valid? Many huge dating mistakes have after the fact been ascribed to contamination. If they have no way of knowing that a sample is contaminated enough to severely distort the results beforehand, this process is a waste of time.
I have seen a separate Creationist web site take a similar position:
One interesting thing is that on the form for submitting rock samples to dating and testing labs, you have to specify how old you think the sample is. Presumably, this is because the labs know the discrepancies in the dating method, and want to choose the “correct date” from the many “bad dates.”
My questions are: how would you respond to such a position? Why are estimated dates required prior to dating? Is radiometric dating as subjective as this gentleman asserts?
Thanks for your consideration,
Robert McNally
From: Daniel Berger
Sent: Tuesday, January 2, 2007 7:10 AM
To: Robert McNally
Subject: Re: Question on Radiometric Dating
Dear Mr. McNally,
There seem to be a couple of crucial misunderstandings behind your interlocutor’s objection to the request for estimated dates; I hope that this will be enough to answer your question. If not, please ask again.
First, the objections to radiometric dating seem to be demanding a mythical “crucial experiment.” Crucial experiments, in which one experiment, by itself, establishes the truth or falsehood of an hypothesis, are not completely unknown, but their mythical, highly celebrated status stems from their rarity. Most scientific statements are based on a preponderance of the evidence; well-established ones are based on an overwhelming convergence of evidence. But (pace Popper) a few contradictory results do not instantly destroy a theory, nor can we expect a single “crucial experiment” to establish one in the presence of contradictory evidence.
To put it bluntly, people make mistakes; but mistakes tend to cancel. It’s much less likely that a whole bunch of competent people will make a whole bunch of mistakes. It is even less likely that all the mistakes will produce results that are consistent with each other — unless the experimenters are in a conspiracy of lies. The larger and more competitive the group (and there are lots of scientists, who compete fiercely for prestige), the less likely that such a conspiracy can be maintained.
In the dating game, there are other bits of evidence than radiometrics. The evidence, taken as a whole, is expected to converge on a single answer (or a range within which the answer lies). In the few cases that it doesn’t do so… well, everybody has had experiments go bad. See the appendix to Michael Polanyi’s “Science, Faith and Society.”
Second, there is no single “radiometric dating” method. Instead, the technique examines several different natural radionuclides, of widely-varying half-lives. For example, C-14 has a half-life of 5730 years; K-40 of 1 billion years; and U-238 of 4.5 billion years. There are differences in detailed chemical behavior that will influence the choice of isotopes depending on the sample being dated — you can’t get a C-14 date on rocks, or a U-Pb date on biological samples — but largely the particular radionuclide you look at will be determined by how old you think the thing is. If the object is thought to be more than a hundred thousand years old, there’s no point in looking for C-14 because it’ll all be gone. On the other hand, you probably can’t get a reliable K-Ar date on something much younger than about half-a-million years old; the result would be indistinguishable from background. The most precise results are probably for objects between about 0.5 half-life and 5 half-lives old, though I could be off a bit because this is not my area of practice.
The estimated age is established by (for example) where you find the item: is it in an undisturbed Etruscan tomb (about 2500 ya)? a modern-human stone-age encampment in Europe (at least 4000 ya, perhaps as much as 60,000 ya, but almost certainly no older than 100,000 ya)? a rock stratum containing a triceratops skeleton (between 65 and 75 millian ya)?
That gives the radiometric workers something to go on. But it also plays into the “convergent evidence” thing. Radiometric dating is not knock-down proof of age (see the continuing controversy over the dating of the Shroud of Turin; the 14th-Century radiocarbon date has been questioned by experts in ancient textiles, for example). But it’s another piece of evidence. If you get a radiometric date that’s wildly different than your estimated date, the evidence is diverging and you need to go back and look at everything again.
For more, see Wikipedia: http://en.wikipedia.org/wiki/Radiometric_dating
The OTHER thing is that a number of Young-Earth Creationist arguments ignore the reality of knowledge within a range. We often can’t know a number specifically; we know it within a certain range. The fact that two radiocarbon dates may place an object in two different centuries (say, the 5th and the 8th AD) doesn’t mean that the object was produced yesterday. In general the fact that we are having difficulty establishing where a number (say, an age) lies within a certain range (say, 15,000 to 50,000) doesn’t mean it’s just as likely to be wildly outside that range (say, 4,000). See, for example, my MadSci answer at http://www.madsci.org/posts/archives/may97/863724333.As.r.html
From: Robert McNally
Sent: Tuesday, January 2, 2007 11:38 PM
To: Daniel Berger
Subject: Re: Question on Radiometric Dating
Dr. Berger,
Thanks for your very clear response. May I have permission to post it to my blog as an article and credit you?
http://ironwolf.dangerousgames.com/blog/
The exchange in which this question came up was in the comments section of this post:
http://ironwolf.dangerousgames.com/blog/archives/196
My interlocutor posted his comments there as “Douglas”, and specifically said he’d like to see a response post from the scientific community.
Thanks again,
Robert
From: Daniel Berger
Sent: Wednesday, January 3, 2007 5:57 AM
To: Robert McNally
Subject: Re: Question on Radiometric Dating
Dear Mr. McNally,
Thank you, I’m flattered. A conservative Christian myself (a member of the ASA, www.asa3.org), I’m of two minds about whether I want to be associated with a blog like yours.
On the other hand, Douglas is calling into question any but the most vapidly general knowledge about the past, which is clearly silly. I’m a Polanyian in epistemology, and his “meal at McDonald’s” example is a denial of the ways of knowing within both science and history. The assumption that he was the one using his credit card is probably the major weakness in the chain of inferences, but it’s not unreasonable, and — were it considered important enough — other corroborating evidence would be brought into play, such as the consistency of this purchase with others he is known or inferred to have made. Arguments based on his purchase records and other papers would probably be used as evidence of whether he was likely to have lent his credit card to someone else. The purchase could not be established with 100% certainty, but why do we demand such?
To a Polanyian, one is free to deny the ways of knowing of a particular community… but one is not free to think that one can know what scientists and historians know if one denies their methods.
As to the assumptions behind science in general and radiometric dating in particular, they are simply that the patterns we observe now also obtained in the past. Within limits, variances in radiometric dates can be accounted for by comparison with samples whose ages are known independently — radiocarbon dates for the past 5000 years or so are calibrated by comparison to tree ring samples — but even if the number were no better than +/- 20%, that excludes values outside that range with a confidence of at least 80%, if I remember my stats correctly.
I would dearly love to know what “huge assumptions about the past” Douglas thinks radiometric dating makes. I’ve other things to do than go delve into YEC sites — classes start Monday, and I’m teaching two new courses that I have to prep for — but the above, and my previous answer, is my best guess at what he was talking about.
You may go ahead and post what I’ve written (it’s not really any different than material I’ve posted on the Mad Scientist Network), but I’d appreciate seeing how it’s redacted.
Daniel J. Berger
From: Robert McNally
Sent: Wednesday, January 3, 2007 5:19 PM
To: Daniel Berger
Subject: Re: Question on Radiometric Dating
Dr. Berger,
I understand your ambivalence. I did not reveal my own philosophical biases when asking my question, because I did not want to unduly bias your answer. But in the question of publishing, I definitely wanted you to know in advance that the general approach I take in my blog is hardly unbiased.
But while I may rail against religion as harmfully dogmatic, I also have many friends who are religious, and I respect them for all that they are. I also believe in people finding common ground. Your common ground with Douglas is that you both believe in God and the Word of God. Your common ground with me, without prejudice to any other possible way of knowing, is that we both respect the modern scientific way of gaining knowledge. This is an important dialog: while I understand that acceptance of science does not imply a refutation of faith in general, many mainstream believers do not— and I believe this misunderstanding harms both the advancement of science and civil society.
So, with your permission, I would be pleased to publish this entire e-mail exchange unredacted except to 1) put the exchange in chronological order, 2) provide contact information only once, 3) put Wikipedia links on terms with which my readers may be unfamiliar, and 4) provide a brief preface directing readers to the original exchange of comments with Douglas.
Regards,
Robert
From: Daniel Berger
Sent: Thursday, January 4, 2007 4:38 AM
To: Robert McNally
Subject: Re: Question on Radiometric Dating
“So, with your permission, I would be pleased to publish this entire e-mail exchange unredacted except to 1) put the exchange in chronological order, 2) provide contact information only once, 3) put Wikipedia links on terms with which my readers may be unfamiliar, and 4) provide a brief preface directing readers to the original exchange of comments with Douglas.”
Sounds good to me. Please go ahead.
Daniel J. Berger
bergerd@bluffton.edu
419-358-3379
www.bluffton.edu/~bergerd
Professor of Chemistry
Bluffton University 87
One University Drive
Bluffton, OH 45817-2104
January 13th, 2007 at 6:37 pm
Thank you for the linkage to my site, and the comment. I also appreciate your curiosity and willingness to investigate and ask questions instead of just ignoring something as hogwash. However, the response of Daniel Berger contains many flaws that I will attempt to refute.
First, the objections to radiometric dating seem to be demanding a mythical “crucial experiment.”
No they don’t. We have many examples of radiometric dating gone wrong. We have exposed many flaws in the process that evolutionary scientists use to come up with very old dates. We have a large body of evidence that demands an explanation.
Most scientific statements are based on a preponderance of the evidence; well-established ones are based on an overwhelming convergence of evidence.
And evolution/old-earth views are not based on an overwhelming convergence of evidence.
It’s much less likely that a whole bunch of competent people will make a whole bunch of mistakes.
What about all of the Greek scientists and others up till Copernicus and Galileo who believed in geocentricism? You constantly hear about scientists who overcame the objections of the entire scientific community to prove their theories. I’m not saying that this is always the case; I’m just saying that there have been cases when a whole bunch of competent people have been wrong. Further, when you have many scientists basing their views on one man’s book that was faulty, and accepting it in spite of practically the entire scientific community before that man, you can end up with problems.
But that’s just preliminaries, now for the meat.
If the object is thought to be more than a hundred thousand years old, there’s no point in looking for C-14 because it’ll all be gone.
This guy is very honest, I like him. Most evolutionists won’t mention that you can’t get millions of years with Carbon dating because the carbon-14 will all be gone, decayed into carbon-12. Thus you cannot get any dates higher than 50,000 years. Those ages that are above the age that Bible lays down are easily accounted for by various things.
On the other hand, you probably can’t get a reliable K-Ar date on something much younger than about half-a-million years old; the result would be indistinguishable from background.
That’s interesting, I didn’t know that. The juice is coming though…
The estimated age is established by (for example) where you find the item: is it in an undisturbed Etruscan tomb (about 2500 ya)? a modern-human stone-age encampment in Europe (at least 4000 ya, perhaps as much as 60,000 ya, but almost certainly no older than 100,000 ya)? a rock stratum containing a triceratops skeleton (between 65 and 75 millian ya)?
I love this. It’s a classic example of circular reasoning. I’ve read about stuff like this but haven’t seen it until now. The conclusions on the dates are interesting as follows:
The Etruscan tomb is fine, since that is supported by the writings of ancient historians.
The modern-human stone-age encampment is even okay, since it actually is 4000-6000 ya.
But the rock stratum containing a triceratops skeleton is the funny one. They assume that the skeleton is 65-75 Ma because the evolutionary paradigm that they fit the skeleton into says that dinosaurs died out long before humans. This isn’t answering the question of how do we know that the triceratops died 65-75 million ya? It just says that it’s that old because it’s that old according to us. I would like to know how Mr. Berger gets the date of 65-75 Ma for the skeleton. The way it usually goes is that they say the skeleton is old because the rock layer is old. The rock layer is old because the skeleton found in it is old.
If you get a radiometric date that’s wildly different than your estimated date, the evidence is diverging and you need to go back and look at everything again.
Once again, I appreciate this person’s honesty, but most scientists do not go back and look at everything again. They just discard the samples as junk and try again until they find a “good” date. There are many cases where a significant percentage of the samples show dates that are wildly different than the estimated date. There are likely many, many more discarded samples that have gone undocumented.
In general the fact that we are having difficulty establishing where a number (say, an age) lies within a certain range (say, 15,000 to 50,000) doesn’t mean it’s just as likely to be wildly outside that range (say, 4,000).
We don’t say that. We say that the original result of 15,000 to 50,000 ya was faulty because of either the procedure, the history of the sample, or the assumptions of the person who got that range. We say that that age is wrong for various reasons, and point out that 4,000 ya is a more likely age for various reasons.
Mr. Berger still did not answer the contention that scientific objectivity is torn askew by the form demanding an estimated age.
Again, thanks for the linkage, I hope to talk to further on this subject. I’ll come back for more discussion.
January 13th, 2007 at 10:02 pm
Althusius,
Thank you for your response. I am going to invite Dr. Berger to respond. But as I do not wish my blog to become an open-ended forum for young-Earth/old-Earth debate, I am going to lay down a few rules.
1) Responses are optional. Lack of response from either viewpoint should not be considered a concession of any point made by the other. Similarly, the failure to refute the any/all content of linked web pages and other cited works shall not be considered a concession to those works.
2) I will allow up to three more responses, two from the old-Earth viewpoint and one from the [edit] young-Earth viewpoint, finishing with an old-Earth viewpoint, since Douglas, a person holding the young-Earth viewpoint started this. This means each viewpoint will have had three chances to speak.
3) Rebuttals can be made by any knowledgeable person of the given viewpoint. I will only allow serious, thoughtful rebuttals in this thread. Anyone else may make brief comments, but I reserve the right to delete any comments I think derail or otherwise detract from the debate.
February 27th, 2007 at 11:18 am
“Once again, I appreciate this person’s honesty, but most scientists do not go back and look at everything again. They just discard the samples as junk and try again until they find a “good” date. There are many cases where a significant percentage of the samples show dates that are wildly different than the estimated date. There are likely many, many more discarded samples that have gone undocumented.”
I love this quote, I do dearly love it because it’s pure unadulterated bullshit. In fact, I just blogged on this today
http://scienceantiscience.blogspot.com/2007/02/radiometric-dating-getting-age-you-want.html
Cheers
Joe Meert
February 27th, 2007 at 2:47 pm
Joe,
Thanks for your response! You’ve got another reader for your blog here.
Robert
May 22nd, 2007 at 11:28 pm
Althusius,
I recently had a brief correspondence with another scientist who happens also to be a Christian (Dr. Keith B. Miller, Dept. of Geology, Kansas State University.) Unfortunately, Dr. Miller is too busy to respond to your rebuttal point by point, although he did provide some general information supporting the current consensus on the age of the Earth that I would be happy to provide to you upon request.
Although I feel no particular burden to find you an opponent for this debate, and so do not intend to contact any more scientists on your behalf (although I will leave this thread open in case anyone qualified would like to respond) I would like to share a final observation stemming from it:
I am struck by the fact that this is really not a debate between non-believers and believers, but between evolutionists (regardless of faith) and Young Earth Creationists. I happen to be both a non-believer and an evolutionist, but to conflate one with the other is making a serious mistake. As I have pointed out elsewhere, Christianity is a mass of schisms, neither able to agree upon how humans can be saved nor upon the right way to lead one’s life— truly “a house divided against itself.” Similarly, it is divided on the issue of the origin of species, and that is simply because the Bible provides no credible alternative to modern science. To a biblical literalist this doesn’t matter, because you accept whatever the Bible says a priori and insist that all other observations be forced to conform, no matter how tortured the logic.
Fortunately, if history is any indicator, the schisms will continue until Christianity adapts completely enough to modern understanding that people who believe as you do end up as rare a minority as flat earthers (and as influential.)
Hey, I’m an optimist.