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Author Topic:   Dating Methodology and its Associated Assumptions
MisterOpus1
Inactive Member


Message 1 of 217 (139558)
09-03-2004 11:56 AM


Hello all,
I've recently ventured a little bit from my personal interest in evolutionary biology and started examining geology a little closer. Specifically, the various dating methodologies. In a recent debate with a young earth creationist, he directed me towards the following website called "Foolish Faith", which is a book that outlines it's arguments for creationism.
More specifically, I was directed towards the following page:
Foolish Faith - Chapter 3: Two Worldviews in Conflict - Radio Dating
which outlines the following assumptions on dating methods:
quote:
The accuracy of these dating methods depends critically on several assumptions.[69] To date a rock by radiometric means, one must first assume:
1.What the initial amount of the parent atoms was at the time that the rock formed.
2.That the original composition of the rock contained no daughter atoms.[70]
3.That neither parent nor daughter atoms have ever been added or removed from the rock.
4.That the decay rate of parent atom to daughter atom has always remained constant.
If these assumptions are correct, then the radiometric dates are correct. However, there is no way to independently test these assumptions. If they are wrong, the method could yield faulty dates that might be far too old.
Now the conclusions that follow are quite a stretch, and even I can depict a number of instances of fallacious logic. But what I have a question about are the assumptions outlined above. Are these assumptions true? I get the distinct impression that they are, in fact, true "assumptions", but that does not necessarily weaken the case for utilizing these assumptions in dating methodology. Furthermore, I also have a notion that the author is incorrect that these assumptions cannot be independently tested, but again I really do not have the knowledge to explain further.
Any thoughts? Thanks for any replies.
Opus1

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Message 2 of 217 (139564)
09-03-2004 12:05 PM


Thread moved here from the Proposed New Topics forum.

PaulK
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Message 3 of 217 (139566)
09-03-2004 12:18 PM
Reply to: Message 1 by MisterOpus1
09-03-2004 11:56 AM


There are some obvious errors and omissions here.
Firstly if 1) is true we don't need 2) to be true. We can just count the number of remaining "parent" atoms. We don't even need to consider "daughter" atoms.
If 2) is true we don't need 1) to be true because we can calculate the original number of parent atoms from the number of "daughter" atoms and the remaining "parent" atoms.
What is more isochron methods account for the number or "daughter" atoms in the original state so we don't need 1) OR 2) to be true.
3) is true but can be checked for by inspecting the rock for signs of chemical or thermal alteration or other damage that might affect the results.
4) is true but there is as yet no relible evidence of a change in radioctive decay rates nor any plausible mechanism by which the decay rates would change significantly and still give consistent results over all the different methods of radiometric dating.
[Added in edit]
Here is the t.o. Isochron dating FAQ
Isochron Dating
Isochron dating itself represents a check on 3) because the samples usually will not fall on the ascending straight line required for a true isochron if the samples have been affected in this way.
This message has been edited by PaulK, 09-03-2004 11:33 AM

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Chiroptera
Inactive Member


Message 4 of 217 (139569)
09-03-2004 12:30 PM
Reply to: Message 1 by MisterOpus1
09-03-2004 11:56 AM


Hello, MisterOpus.
The first three of the alleged assumptions are not assumptions that need to be made in all cases of radiometric dating. If the unit to be dated is heterogenous (for example, it contains crystals of different minerals) then isochron dating can be used. Isochron dating completely eliminates the need for the first two assumptions. Furthermore, it also puts into place a diagnostic that allows the investigator to tell whether assumption 3 is warranted.
In regards to the third assumption, it is currently, and has been in the past, to discover when and how the sample may have been contaminated by the parent or daughter materials, or when some of the daughter materials may have been lost. There is a body of knowledge now that allows a researcher to determine which dating methods will not be accurate based on the composition and physical state of the sample in question.
Also, several different dating methods are often employed. Each isotope has a different half-life, the decay mechanisms are often different, and, most importantly, each of the parents and each of the daughters have different chemical properties, making it unlikely that each of them will be added or lost in just the right amount to make the different dating methods give consistent results. So consistency of dates by different methods is an indication that there has been little or no addition or subtraction of the parent or daughter materials.
Finally, as far as your fourth assumption, there is no reason to believe that decay rates have changed. Decay rates are constant despite any change in chemical or physical environment -- the only exception is that for some nucleotides beta decay is slightly affected by physical conditions (like complete ionization of the atom) that are simply not met in a terrestrial geologic setting.
To change decay rates would require changes in the laws of physics themselves. But there is no indication that the laws of physics, particularly the ones involved in radioactive decay, have ever substantially changed. This is born out by astronomical observations -- the further we see in distance, the further back in time we observe. We see no evidence that the laws of physics have changed -- such an assumption is not warranted by physical data, but by a need to preserve certain a priori religious beliefs.
Furhermore, quantum mechanics shows us that certain conservation laws are tied to the invariance of physical laws. If the laws of physics change, then energy would not be conserved. So far, we have never seen a violation of the law of conservation of energy.

This message is a reply to:
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Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 5 of 217 (139572)
09-03-2004 1:09 PM
Reply to: Message 4 by Chiroptera
09-03-2004 12:30 PM


This is born out by astronomical observations -- the further we see in distance, the further back in time we observe. We see no evidence that the laws of physics have changed...
And even more than that, we see strong positive evidence that the rate of decay of at least some elements hasn't changed in a few billions of years now. Most of the visible light from a supernova is powered by the electron capture decays of nickel 56 to cobalt 56 and then on to iron, with (earthly) half lives of 5.9 and 77 days, respectively. And, imagine that! The light decay curve of a supernova nine billion LY away looks just like one you would calculate using these ground (= present day) radiodecay rates.
Additionally, isotopes used for dating come in several flavors - both alpha and beta decay are used. These, as I understand it, are governed by different forces - on by the Strong and one by the Weak Nuclear Force. It's a rather big coincidence to have ages from four or more different isotopes match up, like for example in the Isua rocks from Greenland, if they all have been tinkered with by some deity......

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 6 of 217 (139792)
09-04-2004 12:19 AM
Reply to: Message 1 by MisterOpus1
09-03-2004 11:56 AM


another good source on dating methods is Dr. Roger C. Wiens
Radiometric Dating
Dr. Wiens has a PhD in Physics, with a minor in Geology. His PhD thesis was on isotope ratios in meteorites, including surface exposure dating. He was employed at Caltech's Division of Geological & Planetary Sciences at the time of writing the first edition. He is presently employed in the Space & Atmospheric Sciences Group at the Los Alamos National Laboratory.
He speaks as a christian as well as a scientist, and pays particular attention to the C versus E debate issues. He also brings the topic down to high school level of discussion.

we are limited in our ability to understand
by our ability to understand
RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}

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Cold Foreign Object 
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Posts: 3417
Joined: 11-21-2003


Message 7 of 217 (144705)
09-25-2004 5:38 PM
Reply to: Message 3 by PaulK
09-03-2004 12:18 PM


The KBS Tuff dating fiasco (1976 "Nature" magazine) used Isochron methods, the very methods that are claimed to ensure errors cannot occurr because of anomalous loss or gain of argon.
The Fitch team and the Berkeley team produced a descrepancy of a half million to one million years. Of course many years later in 1981 the Australian National University bailed out both teams by producing a split the difference dating.
The real thriller of interest is in the rejected dates of 0.5 million years and 17.5 million years "in favor of 2.6 million" originally.
By what scientific criteria was the rejected - rejected and the accepted - accepted ?

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crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 8 of 217 (144729)
09-25-2004 6:30 PM
Reply to: Message 7 by Cold Foreign Object
09-25-2004 5:38 PM


By what scientific criteria was the rejected - rejected and the accepted - accepted ?
Presumably by the same criteria we would use to reject any sort of measurement - convergence or divergence with other, unrelated measurements of the same phenomenon.
Let's say you're on a diet that you invented; you're sure it works. You started at 250 pounds. On the 2nd week of your all-butter diet, you weigh yourself on your bathroom spring scale.
260 pounds. "Impossible!" you say. Maybe the scale is off? You decide to test it. You weigh yourself on a giant pan balance using enormous, calibrated weights. You find yourself balanced by weights equalling 260 pounds. As well, when you put the 100 pound calibrated weight on the scale, it reads 100 pounds.
The clear conclusion? You weight 260 pounds, no matter how much you want to disagree. There's no other explanation for the convergence of the spring scale and the pan balance other than that they both reflect your true weight. (If you were standing in an elevator acelerating upwards, for instance, the spring scale would show a greater weight than the pan balance, because technically the pan balance measures mass, not weight.)
This message has been edited by crashfrog, 09-25-2004 05:30 PM

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NosyNed
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Posts: 8996
From: Canada
Joined: 04-04-2003


Message 9 of 217 (144734)
09-25-2004 6:41 PM
Reply to: Message 8 by crashfrog
09-25-2004 6:30 PM


Not really the point
I don't think your analogy is really to the point crash.

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Cold Foreign Object 
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Message 10 of 217 (144738)
09-25-2004 6:48 PM
Reply to: Message 8 by crashfrog
09-25-2004 6:30 PM


Crashfrog:
I appreciate your response but what determines the reliability of the constancy from which the accepted date was accepted but not the rejected dates ?
If the same dating method was used (and it was) then there must of been (hopefully) a scientific basis to accept and reject the different dates ?
The Isochron method is allegedly billed as the method by which anomalous argon errors cannot occurr. Yet mistakes were made and a choice was made to accept a date and reject others.
What scientific criteria was employed to determine which date to accept ?
I contend the accept date was determined to be the one closest to desired expectations and/or previous ballpark dating already known.
This message has been edited by WILLOWTREE, 09-25-2004 05:49 PM

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jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 11 of 217 (144746)
09-25-2004 7:12 PM
Reply to: Message 7 by Cold Foreign Object
09-25-2004 5:38 PM


The KBS Tuff dating fiasco (1976 "Nature" magazine) used Isochron methods, the very methods that are claimed to ensure errors cannot occurr because of anomalous loss or gain of argon.
While I don't think many really consider the dating controversy over KBS Tuff and the other Tuffs from the area a 'fiasco', it is a good example of how science works to correct itself and provided even more support for evolution and the descent of man.
Here is a great interview with Dr. Ian McDougall where he discusses that very incident as well as the general growth in both knowledge and technique in dating. It also shows how multiple means of dating are used to cross check results.
Also, here is a link to the dates for some of the other tuffs found in the Koobi Fora Formation and it's the other tuffs that date from 700,000 years ago to 3.5 million years ago.

Aslan is not a Tame Lion

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crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 12 of 217 (144751)
09-25-2004 7:26 PM
Reply to: Message 10 by Cold Foreign Object
09-25-2004 6:48 PM


I appreciate your response but what determines the reliability of the constancy from which the accepted date was accepted but not the rejected dates ?
Read my post again, especially the first paragraph, where I answered this.
If you don't believe it was answered in that post then perhaps I didn't understand your question; you might aid me in rephrasing it in that case.

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Cold Foreign Object 
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Posts: 3417
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Message 13 of 217 (144764)
09-25-2004 8:03 PM
Reply to: Message 12 by crashfrog
09-25-2004 7:26 PM


Read my post again, especially the first paragraph, where I answered this.
If you don't believe it was answered in that post then perhaps I didn't understand your question; you might aid me in rephrasing it in that case.
This reply sticking to your guns/initial reply confirms what I already suspected, that there is no reliable benchmark, that it is determined by previously decided needs.
IOW, evos are just confirming dates by previous dates already determined non-scientifically.

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Cold Foreign Object 
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Message 14 of 217 (144766)
09-25-2004 8:14 PM
Reply to: Message 11 by jar
09-25-2004 7:12 PM


Jar:
With all due respect I am not engaged here to "learn" per se.
I have no interest in debating with a website.
I am here to substantiate the unreliability of said dating methods of which I have established a beach head to that end.

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crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 15 of 217 (144770)
09-25-2004 8:17 PM
Reply to: Message 13 by Cold Foreign Object
09-25-2004 8:03 PM


This reply sticking to your guns/initial reply confirms what I already suspected, that there is no reliable benchmark
No, WT, the benchmark is convergence - just like every other thing that has ever been measured.
Convergence is the scientific way that all measurements are validated, in any field. You betray considerable inconsistency by labelling this as "unscientific" in one field but not giving it a second thought in any other.

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