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Reserve
Junior Member (Idle past 3797 days)
Posts: 26
Joined: 03-29-2007


Message 1 of 94 (392452)
03-31-2007 2:11 PM


Hello everyone,

I am new here, however I have read quite a few posts so I am familiar with some of the material. I have a few question that attacks dating negatively.

I have read else where but this link will suffice. It says that Potasium-argon does not work for recent dates. I wonder, why not? why only for ages older than 100kya? Radioactivity is a recently discovered tool from around the 19th century which is about 200 years ago.

So the question is, why can we know the half life of this method in such a short period of time, and not able to use it on anything under the age of 100kya? If we can know the accuracy of the half life within 200 years, we should be able to use it on anything that is 200 years or older.

Potasium-argon does not work for recent dates. It works between about 4.3 bya and 100kya
quote by John at this link, message 4
http://www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=3&t=38&m=4#4

A similar question for radiocarbon dating. If radiocarbon dating is only useful for a maximum date of 100,000 why is it that when dating anything older we would get "back nonsense numbers"? Since the method (Mass spectrometer) counts the atoms, then older objects should give back very low parent atoms. However if we date supposedly older objects and we can count the parent atoms within error, then this tells us that there is an extremely big amount of contamination, or the date of the object is below 100,000 years depending on the ratio.

Radio carbon dating is good for, at the extremes, up to about 50,000 years. Any use of it to date anything suspected to be older will produce a date of about that. It would be stupid to use a measuring tool that is only 50 units long to attempt to measure 100,000 unit long thing.

The physics demands that this be the limit. Up to that limit C14 dating has been well calibrated with various independent approaches.

If one were stupid enough, or dishonest enough, to submit samples of suspected great age for C14 dating one would get back nonsense numbers

qouted by Nosy Ned at this link, message 3
http://www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=3&t=115&m=3#3

Here NosyNed says "suspected great age", however that would be from an evolutionary perspective, from a creationist perspective, why not date objects subjected to the carbon cycle at some point in time and measure their age using radiocarbon?

Edited by Reserve, : wrong word used

Edited by Adminnemooseus, : Made links message specific.


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AdminNosy
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Message 2 of 94 (392613)
04-01-2007 3:27 PM


Thread moved here from the Proposed New Topics forum.
  
Iname
Junior Member (Idle past 1502 days)
Posts: 28
Joined: 06-08-2006


Message 3 of 94 (392629)
04-01-2007 4:06 PM
Reply to: Message 1 by Reserve
03-31-2007 2:11 PM


quote:
It says that Potasium-argon does not work for recent dates. I wonder, why not? why only for ages older than 100kya? Radioactivity is a recently discovered tool from around the 19th century which is about 200 years ago.

From Potassium-Argon Dating under the subsection "Limits to K-Ar Dating"

quote:
At 100,000 years, only 0.0053% of the potassium-40 in a rock would have decayed to argon-40, pushing the limits of present detection devices.

Any lower and it becomes nearly impossible to accurately gauge the amount of decay.

quote:
A similar question for radiocarbon dating. If radiocarbon dating is only useful for a maximum date of 100,000 why is it that when dating anything older we would get "back nonsense numbers"?

Here's the exact opposite problem. After 100K years there isn't enough carbon left to accurately gauge the age. So no matter how much older the object actually is you'll probably get back an age of around 100K years.


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Reserve
Junior Member (Idle past 3797 days)
Posts: 26
Joined: 03-29-2007


Message 4 of 94 (392634)
04-01-2007 4:19 PM
Reply to: Message 3 by Iname
04-01-2007 4:06 PM


Here's the exact opposite problem. After 100K years there isn't enough carbon left to accurately gauge the age. So no matter how much older the object actually is you'll probably get back an age of around 100K years.

But isn't that the misconception, that these methods return dates? These methods return a ratio or a atom count. Then they are put into formulas using some assumptions, THEN you get the date. So you wouldn't get back 100 000 but a very low or zero atom count for carbon dating. This can be translated as around 100 000 years, or just much older. And this would be the interpretation of the low or zero count. We wouldn't get back dates or nonsense numbers. As for your link, it is not working for me. Ill try a different source.

Edited by Reserve, : clarification


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ringo
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Joined: 03-23-2005
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Message 5 of 94 (392635)
04-01-2007 4:19 PM
Reply to: Message 1 by Reserve
03-31-2007 2:11 PM


Reserve writes:

It says that Potasium-argon does not work for recent dates. I wonder, why not? why only for ages older than 100kya?

Would you use your car's odometer to measure your living-room drapes?


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Reserve
Junior Member (Idle past 3797 days)
Posts: 26
Joined: 03-29-2007


Message 6 of 94 (392640)
04-01-2007 4:28 PM
Reply to: Message 5 by ringo
04-01-2007 4:19 PM


Would you use your car's odometer to measure your living-room drapes?

Responses like these, they dont help at all. I do see what you are getting at, except the analogy doesn't work for this. Read the material before the question, and try again.


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Chiroptera
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Posts: 6397
From: Oklahoma
Joined: 09-28-2003


Message 7 of 94 (392642)
04-01-2007 4:29 PM
Reply to: Message 1 by Reserve
03-31-2007 2:11 PM


Hi, Reserve.

I'll give some quick answers here. If they aren't sufficient, then ask some more.

quote:
So the question is, why can we know the half life of this method in such a short period of time, and not able to use it on anything under the age of 100kya?

This is because the half-life of a long lived element isn't measured by waiting for half of it to decay away. One can calculate the half-life simply by calculating the rate at which it decays, that is, by counting how many atoms decay in a second. Of course this is (more or less) the number of clicks you hear on the geiger counter in a second.

I can go through the math if you want, but this is the basic answer.

-

quote:
I have read else where but this link will suffice. It says that Potasium-argon does not work for recent dates. I wonder, why not?

This is because one must measure the amount of Argon-40, which is produced by the decay of Potassium-40, that is present and compare it to the amount of Potassium-40. This will determine what fraction of the original K40 has decayed, and will determine how old the sample is.

Well, if the sample is too recent, then not very much K40 has decayed at all. So there is only going to be a very, very minute amount of Ar40, perhaps so minute that our instruments cannot even measure it. Or so minute that the inaccuracies in measurement will be large compared to the actual amounts. In fact, minute contamination -- Ar40 left in the instrument from the last sample dated -- could very well make it seem like the amount present is much more than in actuality, and so the sample will seem "younger" than it really is.

Of course, for a truly old sample the amount of Ar40 present will be large enough that errors like a small amount of contamination (which should still be avoided if possible) will only be a tiny fraction of what is actually present.

The problem is that many sensitive instruments will rarely read "0" even if the amount is "0". All measurements contain some small error -- however, if the real signal itself is small, then this error will be a large fraction of the value returned by the instrument.

-

quote:
If radiocarbon dating is only useful for a maximum date of 100,000 why is it that when dating anything older we would get "back nonsense numbers"?

This is because, as Iname pointed out, C14 dating is done opposite the way K/Ar dating is. Here we measure the amount of C14 that is present. However, C14 decays very quickly, so very soon only a very, very small amount is left. The amount left is so small that our instruments cannot measure it very accurately, or even at all. Things like background radiation or contamination from a previous sample will make it seem like some C14 is present, and so, again, it may make it appear that the sample is younger than it really is.

-

quote:
from a creationist perspective, why not date objects subjected to the carbon cycle at some point in time and measure their age using radiocarbon?

Well, creationists believe that the earth and all that is contained therein is only about 6000 years old or so. What are they going to do with C14 dates that indicate an artifact is 10,000, 20,000, or even 75,000 years old?


Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Dr Adequate
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Posts: 15987
Joined: 07-20-2006
Member Rating: 4.0


Message 8 of 94 (392647)
04-01-2007 4:49 PM
Reply to: Message 4 by Reserve
04-01-2007 4:19 PM


But isn't that the misconception, that these methods return dates? These methods return a ratio or a atom count. Then they are put into formulas using some assumptions ...

No, let me stop you there.

They are put into formulas which are based on hard evidence, i.e. measurements of the decay rate.

You are suffering from a common creationist disease: when you don't know where evidence comes from, you call it an "assumption".

Scientists know the decay rate of various substances because they have measured them. Scientists aren't allowed to just "assume" things.


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Reserve
Junior Member (Idle past 3797 days)
Posts: 26
Joined: 03-29-2007


Message 9 of 94 (392649)
04-01-2007 4:53 PM


One more thing I would like to add;
It is common for long age believers to say that all dating methods agree with one another. But this is not what I read from this website concerning the potassium argon method.

http://www.creation-science-prophecy.com/K-Ar-dating.htm

To save you guys some extensive reading I'll quote a few lines.

quote:
A very good example of this kind of filtering is a paper by Evernden JF, Savage DE, Curtis GH, James GT: Potassium-argon dating and the Cenozoic mammalian chronology of North America. Am J Sci 1964;22:145-98. This paper is now considered to be a classic paper.

quote:
On pages 171-174 they discuss why all but one potassium/argon date for the Rusinga Island bioites was discarded. Yet they use biotite in an uncritical manor in other areas where the dates they obtained matched their expectations. On Page 174, we can also note: "Unfortunately many of the samples that passed field inspection for suitability and were laboriously collected, later proved unsuitable for dating. . . . Thus, of some 65 samples collected by M. Skinner, only 10 could be used." Other creationists such as Paul Giem (in his book, Scientific Theology see references below), have thought: "It might have been interesting to know why such samples proved unsuitable for dating, and what their potassium/argon dates were."

quote:
It is amazing that a paper that only reports 1/6 of the data, is also considered to be a classic paper. Paul notes: "It is interesting to speculate what would happen if an article in chemistry or medicine were submitted with perhaps 1/6 of the data reported."

From this I really do not agree with people saying that radiometric dating is carved in stone and only few minor problems ever prop up, according to this, only 1/6th of the data was used which translates to 5/6th of the data not working out...

Is there something wrong with this person's view or are evolutionists and long agers trying to hard to make radiometric dating look like infallible proof of an old earth.


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ringo
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Posts: 14015
From: frozen wasteland
Joined: 03-23-2005
Member Rating: 1.7


Message 10 of 94 (392650)
04-01-2007 4:56 PM
Reply to: Message 6 by Reserve
04-01-2007 4:28 PM


The analogy works just fine if you really do see what I'm getting at.

You can't use your car's odometer to measure your drapes because it's only calibrated to tenths of a mile. Since it can only measure to the nearest tenth of a mile, anything less than a tenth of a mile will return... a tenth of a mile. Every set of drapes you measure will be a tenth of a mile, so there's no point in measuring at all. Just go to the store and order "drapes".

Similarly, the K-Ar method is calibrated to - let's say - millions of years. Since it can only measure to the nearest million years, anything less than a million years will return... a million years. Every young sample you measure will be a million years, so there's no point in measuring at all.

That doesn't mean that either your odometer or K-Ar dating is inaccurate.

Don't take the exact numbers too seriously - I don't know what the actual sensitivity of K-Ar is, off hand. But the principle is sound and the analogy is sound.

If that's not the objection you have, then please be more clear in expressing it.


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Dr Adequate
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Message 11 of 94 (392653)
04-01-2007 5:01 PM
Reply to: Message 1 by Reserve
03-31-2007 2:11 PM


I have read else where but this link will suffice. It says that Potasium-argon does not work for recent dates. I wonder, why not?

But you didn't "wonder" so much that you looked it up.

Again, this is typical creationism. Your case is built on things which you personally don't know.

The answer is simple. When rock is molten, as it is when igneous rocks are formed, then the argon, being a gas, boils out of it. But not quite all of it, and the precise quantity will depend on the particular volcano, how hot it was, the original composition of the rocks, and so forth.

This can be verified by measuring the argon content of fresh volcanic rock.

So the question is, why can we know the half life of this method in such a short period of time, and not able to use it on anything under the age of 100kya? If we can know the accuracy of the half life within 200 years, we should be able to use it on anything that is 200 years or older.

Because knowing the half-life is not sufficient: we would also have to know the exact amount of residual argon which did not boil out of the rock.

Edited by Dr Adequate, : No reason given.

Edited by Dr Adequate, : No reason given.

Edited by Dr Adequate, : No reason given.


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Chiroptera
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Posts: 6397
From: Oklahoma
Joined: 09-28-2003


Message 12 of 94 (392656)
04-01-2007 5:24 PM
Reply to: Message 9 by Reserve
04-01-2007 4:53 PM


On pages 171-174 they discuss why all but one potassium/argon date for the Rusinga Island bioites was discarded.

What was their discussion? It seems a bit unfair to blame them for deciding that some of the dates were unreliabe without hearing their side of the story.

-

Paul notes: "It is interesting to speculate what would happen if an article in chemistry or medicine were submitted with perhaps 1/6 of the data reported."

But according to the article they did report the dates.

Now why in the world would they publish the fact that they discarded the dates, for the entire world to read, if there was something fishy going on?

Evernden et al. can be accessed online, although I don't want to pay to see it. If anyone has access to a university library, they can probably read the article themselves. All I can get is the abstract:

Potassium-argon ages of sanidines, biotites, and basalts are found to be in essential agreement with time-sequential dating of Tertiary land mammals. A detailed time scale of the Tertiary based on an age breakdown is given.

Now, why would they say this in the abstract if someone reading the article could tell that this was not true? In fact, if they were trying to hide something, if they were trying to dupe someone, why would they say anything at all?

Something doesn't seem right in this accusation. If Evernden et al. were frauds, they seem to be incompetent frauds. How would their findings be published if they were so obviously fraudulent?


Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Dr Adequate
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Posts: 15987
Joined: 07-20-2006
Member Rating: 4.0


Message 13 of 94 (392662)
04-01-2007 5:43 PM
Reply to: Message 9 by Reserve
04-01-2007 4:53 PM


On pages 171-174 they discuss why all but one potassium/argon date for the Rusinga Island bioites was discarded. Yet they use biotite in an uncritical manor in other areas where the dates they obtained matched their expectations. On Page 174, we can also note: "Unfortunately many of the samples that passed field inspection for suitability and were laboriously collected, later proved unsuitable for dating. . . . Thus, of some 65 samples collected by M. Skinner, only 10 could be used."

Well there is clearly something wrong with this nonsense, 'cos they start off by saying that they "all but one" of the dates were "discarded", and then they say that 10 were used.

They're not even talking about the same samples, are they?

If the creationists can't consistently tell the difference between 1 and 10, is it possible that they've misunderstood the rest of the paper?


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RAZD
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Posts: 19332
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Message 14 of 94 (392665)
04-01-2007 5:55 PM
Reply to: Message 9 by Reserve
04-01-2007 4:53 PM


known sources of errors is part of knowing how to use a method
Welcome to the fray Reserve,

One more thing I would like to add;
It is common for long age believers to say that all dating methods agree with one another. But this is not what I read from this website concerning the potassium argon method.

There are many reasons why specific dates can be unreliable. The scientists doing the dating know these factors and base their approach on them.

For instance Carbon 14 dating (C14) is based on the uptake of atmospheric formed C14 during the life of an organism and then its subsequent decay after death of the organism. IF the carbon taken up by the organism does not have any atmospheric carbon, it will not have the atmospheric formed C14 and the dates derived from the analysis will be in error.

A common and well known source of this kind of error is where shellfish or animals that eat shellfish get their carbon from the sea-bed instead of the atmosphere. This is known as a "reservoir" effect, and there are published documents detailing where and how much such effects occur around the world.

Creationist con-artists (what I call "creatortionistas") often go to these sites and make measurements, knowing full well that the results will be bogus, false, erroneous, etc, and they then cite this as evidence that C14 dating does not work. All they really show is that they can misuse science and con gullible people.

If you want to see a discussion on the validity of properly applied C14 dating and the evidence for an old earth that does not rely on radiometric dating see Age Correlations and an Old Earth: Version 1 No 3 (formerly Part III). There is an updated version at Age Correlations and An Old Earth, Version 2 No 1, however it is a new topic that has not been promoted yet. It has a Message 11 (feel free to reply to that information here).

It is also normal to take several samples and to date items by different systems as ways to reduce the possibility of errors.

An excellent resource for learning about radiometric dating methods, problems, limitations and applications is:

Radiometric Dating
A Christian Perspective
Dr. Roger C. Wiens
http://www.asa3.org/ASA/resources/Wiens.html

Feel free to ask questions.

Enjoy.

Edited by RAZD, : poyt


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Coragyps
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Posts: 5299
From: Snyder, Texas, USA
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Message 15 of 94 (392672)
04-01-2007 6:26 PM
Reply to: Message 1 by Reserve
03-31-2007 2:11 PM


Hi, Reserve! Welcome!

It says that Potasium-argon does not work for recent dates. I wonder, why not? why only for ages older than 100kya? Radioactivity is a recently discovered tool from around the 19th century which is about 200 years ago.

That first part is nearly true, but there's a variation of potassium-argon dating, called argon-argon, that's been used to date the Pompeii-burying eruption of Vesuvius. That was in 79AD, by historical and tree-ring dates, and argon-argon got it right with an error of +/- 94 years. There, but you must register for free to read it.

Here's the abstract:

Laser incremental heating of sanidine from the pumice deposited by the Plinian eruption of Vesuvius in 79 A.D. yielded a 40Ar/39Ar isochron age of 1925 ± 94 years ago. Close agreement with the Gregorian calendar-based age of 1918 years ago demonstrates that the 40Ar/39Ar method can be reliably extended into the temporal range of recorded history. Excess 40Ar is present in the sanidine in concentrations that would cause significant errors if ignored in dating Holocene samples.

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