More about Potassium Argon Dating....

[youngborean]

http://id-archserve.ucsb.edu/Anth3/Cour ... ating.html


There is something that I suspected of these dating methods, that the study posted by the Creation researchers seemed to point out. It is best illustrated by some information on the website I posted. We move out of statistical relavance when using this method to date anything less than 100,000 years. That coupled with the idea that precentage errors can mean a lot of time when we are talking exponential decay. So my point is this. How can we even say that a volcanic rock is less than 100,000 years compared to 1,000,000 years old assuming some error, etc.? Is then a fair method to use to refute suggested dates for an early earth since the method is unable to detect a volcanic rock that is early, like 7000 years ago? Choosing this method must therefore assume that a rock is older than 100,000 years old. Now I would argue that the research project on answersingenesis that shows the volcano from 60 years ago being analyzed as being 1.5 million years old is not novel science. That is becasue that result is inherent in the margin of error. It only clearly showed the limitation of this method.

[youngborean]

A false positive occurs because all readings would still show a date. We still get results when dealing near control limits. But the argon would not be undectable, the instrumentation would still likely detect "things" due to noise or experimental error, because it would theoretically still be there but the ratios and detection would be too random to show a difference. The result of this could be very significant if we were to measure a rock that was 10 years old. As for the upper age threshold of the dating billions of years, you are absolutely correct. I don't have a model to describe these results and could not disprove their theories at this point, nor would I try. Because there is no model that can test the age of rocks completely. And you theoretical argument also makes sense. I would just say again that using this data to disprove dates for creation is incomplete because the method cannot account for the proposed dates of geology as proposed by people who believe in a young earth. It is a curious method that proposes to measure time without being verified by a control.

[nikolayevich]

Well, the problem lies in that there's no way to actually know without a shadow of a doubt how old a rock or anything is without watching it being created and timing it.

If you want to be able to date something at all, you have to accept the results and not say they're wrong,

Isn't that fairly unscientific? To simply accept, because otherwise you won't have answers? I know that this is prevalent but does it come with wisdom? (speaking of us all, not you personally)

...because let's say I have something that dates 10,000 years ago with perfect accuracy. How can you confirm that it's 10,000 years old, or that it's 8,000 and I'm just getting a "perfectly" false reading. Any system could theoretically be completely wrong without us know. You either accept that the systems are not possible to be proven without a shadow of a doubt, or not date stuff.

Or... recognize inherent problems with current methods and try to find better ways to calculate age. Not having a better replacement isn't reason to invest so much trust in what known to be flawed.

It makes me think of certain teachings known to be spurious in the community but which are not removed from highschool biology textbooks, because there aren't replacements for the concepts which they engender. It is a different issue based on the same line of thinking- What should we do without replacement for this thing [which we feel is] fundamental to historical science? We often just let it run its course.

You could get a rock that could look new while actually being old, but how would you mistakenly read that the rock is millions of years old when it's new? The argon wouldn't be there...

It's based on the assumption that rock with measurable amounts of Ar-40 is always older than 100,000. A statement predicated on its assumption is generally not so reassuring.

[juliod]

How can you ensure that those rocks were not less than 100,000 years?

Because of the potassium-argon dating. You were questioning it's accuracy at dates newer than 100K BP, not older than than.

A creationists assertion is that all rocks are under 100,000 years old.

The YECs say less than 10,000 years old.

The only way you could disprove that theory is to have a test that could test in that range and past that range to establish a control.

This was done long ago, and using methods that require no sophisticated methods. Dendrochronology goes back as far as 15,000 BP. Ice cores with annual layerings also.

And one of the earliest things that showed the great age of the earth was a study of the volcanic cones on and around Mt. Etna. Knowing that only one cone had come into existance in recorded history, the person (I forget who it was) looked at the dozens of cones around the volcano, and the hundreds covered up by Etna itself and then exposed by erosion. While no absolute date could be given, the landscape shows that the Etna area is much older than allowed by biblical chronology.

But if you choose this method to measure a rock, you must first assume that the rock is over 100,000 years old.

Which is entirely reasonable given the comprehensive evidence of the extreme age of many geological features.


DanZ

[ENIGMA]

A false positive occurs because all readings would still show a date. We still get results when dealing near control limits.

Although the time-translated margin of error will indicate the occurrence of such samples.

But the argon would not be undectable, the instrumentation would still likely detect "things" due to noise or experimental error, because it would theoretically still be there but the ratios and detection would be too random to show a difference.

Would this be to determine the age of a given sample or the half-life of a given isotope?

If to determine a sample then yes, it would yield a large margin of error and indicate that an isotope with a smaller half-life is likely needed to get a decent approximation.

If to determine the half-life of a given isotope, one can get around this bottleneck by starting with several large samples composed purely of a given isotope and then wait some specified period of time (a year, decade, etc, with the understanding that the larger the sample size, statistically the less distortion and thus the less time needed to get acceptable results.) After the elapsed period of time, measure the samples, interpolate the results, and determine a best fit exponential decay curve.

The result of this could be very significant if we were to measure a rock that was 10 years old.

Since the distortions are errors in measuring the quantity of each kind of isotope, having a larger sample size of isotope decreases the impact of such deviations from the actual results as per the law of large numbers. Also, having several independant measurements dramatically lessens the likelyhood of getting data systemically distorted by bad equipment.

As for the upper age threshold of the dating billions of years, you are absolutely correct. I don't have a model to describe these results and could not disprove their theories at this point, nor would I try. Because there is no model that can test the age of rocks completely. And you theoretical argument also makes sense. I would just say again that using this data to disprove dates for creation is incomplete because the method cannot account for the proposed dates of geology as proposed by people who believe in a young earth.

Not can't, doesn't. Big difference. If the dates for creation were that recent then all such rocks should have negligible or near-negligible isotope decay.

To pass the 6k-10k year threshold, one doesn't even need to reference K/Ar dating. Carbon would suffice quite nicely seeing as it happens to be scaled to work without much distortion well before and well after that time period.

[Gollum]

Perhaps this http://www.asa3.org/ASA/resources/Wiens.html#page%2019 will clear it up.

It was written by a christian scientist (lower case ... not an L. Ron Hubbard Christian Scientist) who is also an expert in Radiometric dating techniques.

As he says in summary, there are many radiometric dating techniques and a competent expert selects the one(s) most appropriate to the sample being measured. You get the false positive dating results when you select an inappropriate technique.

[Jose]

Welcome to the fray, Gollum! Your link helps a lot (or, at least, I think it should). The critical point is that no one relies on a single isotope for dating. There's a bunch of different ones, with different half-lives, that can be used for different time ranges. The key is to choose the right one for the right material. If you choose the wrong one, you are guaranteed not to get a valid answer.

I don't know if there is a systematic problem in teaching how this works, or whether there are intentional misrepresentations going around, but it does seem that carbon dating and K/Ar come in for the most criticism as being "unreliable." Carbon is a target because it provides answers in the time frame that should span biblical creation. K/Ar is a target because it gives answers that are vastly different from the predictions of biblical creation. Either one, if true, would seem to rule out the biblical creation story, at least the young-earth version thereof.

[youngborean]

I don't know if there is a systematic problem in teaching how this works, or whether there are intentional misrepresentations going around, but it does seem that carbon dating and K/Ar come in for the most criticism as being "unreliable." Carbon is a target because it provides answers in the time frame that should span biblical creation. K/Ar is a target because it gives answers that are vastly different from the predictions of biblical creation. Either one, if true, would seem to rule out the biblical creation story, at least the young-earth version thereof.

My point is precisely that. That a researcher has to choose a technique for dating based on preconcieved notions of age. This hardly provides a method for a definitive techinque for assessing the age of the earth. Until we have a method that can cablibrate accurately past 10,000 years, it is very difficult to assume that we have anything that isn't theoretical. The fact that we can't create 1 test for a material that spans from 0-millions of years creates problems. This christian (admittedly) article cites an interesting example that would seem to occur often when mixing methodolgies.

http://www.answersingenesis.org/creatio ... dating.asp

So date which would take precedence when this overlapping occurs?

I think both C14 and K-Ar dating come into question because both are only able to give half the picture, and have to be filled in with assumption. Until a well calibrated method that spans from 0-millions of years, a young earth model is completely within reason.

[Jose]

My point is precisely that. That a researcher has to choose a technique for dating based on preconcieved notions of age. This hardly provides a method for a definitive techinque for assessing the age of the earth.

Not so. With adequate material (usually the case with your average lava flow), one can use all possible techniques. One asks which ones provide reliable data (ie, ratios of parent isotope to daughter isotope that are within measurable range, without great error in measurement). One takes multiple samples, and performs multiple tests. One also correlates the conclusions with other information to try to obtain an independent assessment of reliability.

We know enough now, however, that the researcher usually does choose the isotopes beforehand. This is not a bias in terms of "trying to get a certain age" but rather, having some knowledge of the age range already.

Until we have a method that can cablibrate accurately past 10,000 years, it is very difficult to assume that we have anything that isn't theoretical. The fact that we can't create 1 test for a material that spans from 0-millions of years creates problems.

But we do have methods that can calibrate past 10,000 years. As noted above and elsewhere, ice cores do so very nicely. Other isotopes do, too. However, because god didn't give us one isotope that can give measurements from 0 years to 4.5 billion years, we are stuck with what we have. There's no conceptual problem here. We measure the distance from New York to Boston in miles, because it would be inconvenient to measure it in millimeters. We measure the sizes of mold spores in micrometers, because it would be impossible to measure the sizes using a ruler the length of a light-year. We are quite happy using different yardsticks for different physical distances; here, we are using different yardsticks for different temporal differences. The principle is the same.

This christian (admittedly) article cites an interesting example that would seem to occur often when mixing methodolgies.

http://www.answersingenesis.org/creatio ... dating.asp

So date which would take precedence when this overlapping occurs?

Neither one. It is necessary, in the case of such obvious conflict, to figure out the source of the discrepancy. Answers In Genesis doesn't do this; it simply concludes that C14 dating is unreliable, and therefore, all radiometric dating is unreliable. Was the coal sample "reworked" from much younger sediments? Was the sample handled properly during preparation? How many replicate measurements were made--enough to be statistically reliable? Had the coal sample been altered through weathering or burrowing or some other process that might contaminate the sample? Alternatively, what is the evidence that the strata really are Miocene? In short, there are a great many unknowns in the AiG story. This is why it is essential to look in refereed journals, for which the rules are quite strict: the reader must be given enough information to assess the validity of the results for themselves, and to draw their own conclusions. If there is not enough information for this, the paper should be rejected (although not all are, but that's another issue).

I think both C14 and K-Ar dating come into question because both are only able to give half the picture, and have to be filled in with assumption. Until a well calibrated method that spans from 0-millions of years, a young earth model is completely within reason.

No, neither one comes into question on the basis of their being effective at different ages. What is questionable is using one to cross-check the other. Fortunately, there are alternate methods for cross-checking C14 (dendrochronology, ice cores, etc), and there are alternate isotopes for cross-checking K/Ar. There really is remarkably good agreement of the various methods, and a very large number of samples. Because of the agreement and consistency of the vast majority of analyses (and the recognition of the errors where inconsistency has been found), it really isn't reasonable to conclude that the techniques are just not reliable.

This is why it has been suggested that the rates of decay were vastly different around the time of creation, as well as the values for energy release during radioactive decay. That is, we can get the measured ages to match a young earth only if we change the laws of physics--several of them--which would require divine intervention. That is, a few mistakes in measurement, however widely advertised, do not negate all of the accurate measurements. In the face of the accurate measurements, it is hard to come up with a reasonable justification--beyond faith--for a young earth.

[Gollum]

My point is precisely that. That a researcher has to choose a technique for dating based on preconcieved notions of age.

Yes of course. By way of analogy. I have a car with an odometer that measures distance. I also have a 4-meter tape measure. If I want to determine the width of my living room I make a guess about it in order to select the correct measurement device ... in that case; the tape measure. If I wanted to know how far it was to the nearest ocean (about 1,000 km) then I take another guess and select the car with odometer.

The point is that my "guess" just allows me to select the most likely proper measurement device. It doesn't prejudice the results that I get.

Obviously the odometer, calibrated as it is to the nearest hundred meters, is going to tell me that the width of my living room is zero ... or more precisely it is less than 100 meters. Similarly, the tape measure tells me that the nearest ocean is more than 4 meters away. Both results are correct ... but they speak to the limitations of the measurement devices and not to definition of the actual dimensions being measured.

Sorry to go on about something so obvious. It did seem that the selection of a radiometric dating technique which proceeds by much the same mechanisms, was being unfairly cast as introducing bias or errors when in fact, the whole purpose of that selection is the avoidance of those errors.

[Jose]

You make a good point, Gollum. The question is, for the non-expert, can it seem as if we make a guess when we do this, and then choose a technique that will give an answer similar to the guess? Your tape measure vs odometer is a good analogy that, I hope, puts the problem into a more accessible form.