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Author Topic:   Assumptions involved in scientific dating
JonF
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Message 6 of 222 (789101)
08-10-2016 1:51 PM


Copied from another forum
Part the first: "assumptions" (I prefer "premises") underlying radiometric dating

A. The amount of decay (daughter) product present at solidification must be known.

It certainly is true that the amount of initial daughter must be known. It is not true that this is assumed. Only K-Ar dating (seldom used any more) is susceptible to error due to "excess argon" present at solidification, and we know that such is rare. (E.g. in 40Ar-36Ar Analyses of Historic Lava Flows Dalrymple found that one of 26 samples had significant excess argon, 18 did not have excess argon, and seven had a little excess argon that would be insignificant after a few million years, compared to the decay product.) The K-Ar method, beloved of creationists because it is possible for it to be fooled but not used much anymore, relies on the premise that the gaseous daughter product escaped from the liquid melt. Rational sample selection (e.g. avoiding the situations in which this is known to be problematic such as pillow lavas that solidified very quickly underwater) almost always leads to reliable dates, as shown by the excellent agreement of K-Ar dates with more robust methods (such as shown at Consistent Radiometric dates). Irrational and fraudulent sample selection, often practiced by creationists, can produce obviously false results; but this is a problem with creationists, not with the method.

But the various methods in wide use today are not susceptible to such errors. Isochron methods use the chemical/mechanical identity of various isotopes of the daughter product to produce the initial quantity of daughter product as a result of the analysis, not a premise (Isochron DatingHelium Diffusion Rates Support Accelerated Nuclear Decay, pp 3-4:

quote:
Samples 1 through 3 had helium retentions of 58, 27, and 17 percent. The fact that these percentages are high confirms that a large amount of nuclear decay did indeed occur in the zircons. Other evidence strongly supports much nuclear decay having occurred in the past this point because many creationists have assumed that “old” radioisotopic ages are merely an artifact of analysis, not really indicating the occurrence of large amounts of nuclear decay. But according to the measured amount of lead physically present in the zircons, approximately 1.5 billion years worth—at today’s rates—of nuclear decay occurred. Supporting that, sample 1 still retains 58% of all the alpha particles (the helium) that would have been emitted during this decay of uranium and thorium to lead.

The widely used Ar-Ar method is similar to isochron methods in that it is not affected by any premises about the amount of initial daughter. A sample is irradiated to convert some of the 40K to 40Ar, and a known-age sample is irradiated at the same time to find the percentage of the 40K that was converted. The basic age determination could be made by back-calculating the amount of 40K and using the K-Ar dating equation... but there's another important wrinkle. The sample is heated by a laser, the 40Ar and 40K released is measured and used for dating, the sample is heated a little hotter, the 40Ar and 40K released is measured and used for dating, and so on until the sample is vaporized. It should be obvious that if there is no excess argon or argon loss all those dates will be the same. If we plot the heating step number on a horizontal axis and the date obtained from that heating step on a vertical axis we would get a horizontal line:

It is a fact that if there is excess argon the left side of the "plateau" will be higher than the middle, and if argon has been lost it will be lower. But if there is a significant plateau in the remainder of the plot it still indicates the real age. (Of course sometimes there's no plateau at all and the method fails). A good example of this is 40Ar/39Ar Dating into the Historical Realm: Calibration Against Pliny the Younger (free registration required), in which the Berkeley Geochronology Center dated lava from the 79 AD eruption of Vesuvius, which contained excess argon. Alas, they did not produce a plot similar to the one above.

More detailed information on Ar-Ar can be found at Argon-Argon Dating: What is it Good For?.

B. Relevant material must not be gained or lost after solidification.

Again, K-Ar is susceptible to this kind of error, but we know it happens infrequently because K-Ar correlates so well with more robust methods. Other methods at least indicate the issue, and some can often produce a valid date if material has been gained or lost.

Isochron methods (see reference above) will not produce a straight line if this issue arises. Ar-Ar dating and U-Pb dating also indicate when relevant material has been gained or lost (almost always lost). Ar-Ar can often produce a valid date if a plateau is present such as shown in the bottom plot below:

The argon lost over the years is indicated by the left side, where most of the loosely bound argon has already escaped and the indicated age is less than the real age..

U-Pb dating also indicates when relevant material has been gained or lost (almost always lost), and can often produce a valid date. There's somewhat technical explanations at Radiometric Dating, heading "The U, Th, Pb System" and The U-Th-Pb System: Zircon Dating.

C. Constant decay rate.

The RATE group concluded that the only viable explanation for radiometric dates in a young Earth is Accelerated Nuclear Decay (AND). They attempted to prove the existence of such. There are many refutations of their claims on the Web: I recommend RATE (Radioactivity and the Age of The Earth): Analysis and Evaluation of Radiometric Dating and Radioisotopes and the Age of the Earth. However, AND is easily disproven by the fact that we do not see the heat and radiation effects that would be produced by AND; a molten Earth and no life on it except perhaps for some thermophilic bacteria..

C.I. Heat

Condensing 5E8 years of decay into one year or less would produce an immense quantity of heat. From the first RATE book, Introduction, page 8, Vardiman writes:

quote:
One major obstacle to accelerated decay is an explanation for the disposal of the great quantities of heat which would be generated by radioactive decay over short periods of time. For example, if most of the radioactive decay implied by fission tracks or quantities of daughter products occurred over the year of the Flood, the amount of heat generated may have been sufficient to vaporize all the waters of the oceans and melt portions of the earth’s crust, given present conditions.

Snelling quantifies this problem in Radiohalos in Granites: Evidence for Accelerated Nuclear Decay, page 183:

quote:
To put this heat problem in perspective we can quickly do a rough estimate of the effect of just the accelerated nuclear decay, say 500 million years worth (at today’s rates), but instead taking place in a single year (the Flood year). The following values of the relevant parameters were obtained from Stacey [1992]:

  • the typical heat production in a granitic pluton from radioactive decay of U, Th, and K is ~10 -9 W/kg,
  • the specific heat of granite is ~700 J/kg-K, and
  • the number of seconds in 500 million years is ~1.6 · 10 16 sec.

Thus the adiabatic temperature rise =

((1.6E16 sec) * (1E9 W/kg))/(700 J/kgK) = 22,400 K

This is equivalent to a temperature rise of more than 22,000°C, which is sufficient, of course, to vaporize a granitic pluton many times over!

Another approach is to assess the heat production in the zircons themselves within the granitic rocks. Note that the U concentrations in the zircon grains can be on the order of 1% by mass of the grains. If the mass of a zircon grain relative to the mass of the biotite crystal that includes it is 0.01, then with the current heat production from radioactive decay of U of 10 -4 W/kg, the average heat production in the biotite enclosing that zircon grain is 10 -8 W/kg, which is only an order of magnitude higher than the value used above for a typical granite. Thus the adiabatic temperature rise in the biotite as a result of 500 million years worth of accelerated radioactive decay is an order of magnitude higher than the value obtained for the granitic rock as a whole. Of course, the biotite crystal and the zircon grain included in it would be vaporized! So whichever way the calculation is made, there is no denying that there is a genuine heat problem associated with accelerated nuclear decay.


Obviously if the Flood is taken to have occurred more recently, the numbers would be different but just as disastrous. The only hypothesis I've seen proposed to solve this problem is Humphreys' cosmic expansion theory, in which the Earth is cooled by the expansion of space. The problems with this hypothesis are discussed in detail at Nonexistence of Humphreys’ “Volume Cooling” for Terrestrial Heat Disposal by Cosmic Expansion and Flaws in a Young-Earth Cooling Mechanism. But without even considering whether the hypothesized mechanism is possible we can see a major problem with it. The cooling would have to be applied not evenly throughout the Earth, but very selectively: more cooling where there's more radioactive elements (e.g. rocks) and less cooling where there's fewer radioactive elements (e.g. oceans and living creatures). That just isn't going to fly. Humphreys acknowledges the problem in Young Helium Diffusion Age of Zircons Supports Accelerated Nuclear Decay, pp 73-74:

quote:
The real problem is how to keep non-radioactive materials from getting too cold at the same time. I have not had time to pursue this part of the idea further, so here I can only outline a speculation that may turn out to provide a good explanation later. If the "fabric" of space is a real material, as Scripture implies [Humphreys, 1994, pp. 67–68], then it must have a temperature. I speculate that its temperature might set a minimum on how much heat could be transferred to the fabric during rapid expansion. For example, equation (31) might become:

T = -2H(T - Tmin) (32)

where Tmin is a minimum temperature that might depend on the amount of time dilation occurring at the moment. If Tmin were about 300 K during the Genesis Flood, then creatures aboard the Ark could stay warm. Though this is sheer guesswork now, I am confident that a good explanation exists (whether or not we can find it). That is because (a) the evidence convinces me that accelerated nuclear decay did indeed occur, and (b) as one of Noah’s descendants, I know that his family did not freeze to death aboard the Ark!


Note that he's not really presenting a viable hypothesis, and note the reality of Biblical literalism overlying the false claim of scientific inquiry.

C.II. Radiation

Condensing 5E8 years of decay into one year or less would also produce an immense quantity of radiation. Again from the first RATE book, Introduction, page 8, Vardiman writes:

quote:
A second obstacle to accelerated decay is the ability of life to cope with the great quantities of ionizing radiation that would have been generated by accelerated decay over short periods of time. This is particularly so with respect to 40 K in animal and human bodies. For example, Noah and his family and the animals would likely have been subjected to deadly concentrations of radiation during their stay on the ark if accelerated rates of decay occurred during the Flood. Although the water beneath the ark would have probably protected him from radiation from the earth below, if Noah had similar concentrations of K in his body as we do today, radioactive decay from within his body would have been very destructive.

Note that this assumes that the heat problem is solved, so there would be water remaining to shield Noah from the radiation from the rocks. I haven't looked into whether this shielding is realistic (there is uranium dissolved in sea water).

I haven't seen any YEC quantifications of this problem, but it turns out it isn't difficult. There have been many studies of radiation dosage due to 40 K in humans, e.g. Assessment of the doses received by the Cuban population from 40K contained in the body: modelling based on a neural network, Body potassium content and 40K radiation dose to Iranian subjects, and Body potassium content and radiation dose from 40K to the Slovak population. Note that, for decay that produces beta radiation in a human body, 1 microGy = 1 microSv = 1 micro Sievert. All these sources agree that the radiation dosage in the human body due to decay of 40 K is in the range of 100-200 microSv/year, and I doubt that all the subjects were heavy banana consumers. Let's take 100 microSv/year for simplicity, and see what dosage would result from condensing 5E8 years of decay into one or less. It's pretty simple:

5E8 *100*1E-6 = 50,000 Sv

Again a more recent flood would yield a different but essentially similar number. How bad a radiation dose is this? At Lethal dose (LD), 4-5 Sv is listed LD 50/30, meaning 50% of the people exposed to this die within 30 days. At How Much Radiation can the Human Body Safely Receive? the external background radiation on Earth is about 2.4 mSv, and an exposure of 6 Sv is equivalent to 90% death rate, increasing to 100% at higher levels. Obviously dosing Noah et. al. with 10,000 times the LD 50/30 would turn the ark into a casket of rotting flesh (or maybe zombies!!).

The only solution I've seen proposed for this problem is that living things didn't have any 40 K in their bodies until after the Flood. In Summary of Evidence for a Young Earth from the RATE Project, page 765, Vardiman et. al. write:

quote:
One solution has been offered that possibly could mitigate this problem—namely, that the 40K we measure in plants and animals today is the result of the Genesis Flood itself. The RATE team believes an attempt should be made to test for 40K in the bodies of pre-Flood insects which were trapped in amber during the Genesis Flood and were thereby protected from subsequent contamination.

I would sure like to see some YEC try to defend this one! Of course there's a big fat pile of observations and analyses that establish that there has been no significant change in decay rates for many billions of years


  
JonF
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Message 46 of 222 (798944)
02-06-2017 5:09 PM
Reply to: Message 42 by ICANT
02-06-2017 1:32 PM


Re: Assumptions are not wild guesses
The first assumption you have to make is that the universe is x years old, A constant rate of decay, an isolated system in which no parent or daughter element can be added or lost, and a known amount of the daughter element present initially.

Addressing them in order, nope, nope, nope, and, finally nope. You do not have an iota of a clue about radiometric dating.

But I don't care what age you tell me a particular rock is I will disagree with you as I believe it is much older than you do, because of what I read in the Bible.

I would be glad to explain why you do not have an iota of a clue about radiometric dating, but you make it clear you are not interested in facts.


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JonF
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Message 47 of 222 (798952)
02-06-2017 5:20 PM
Reply to: Message 44 by Taq
02-06-2017 2:24 PM


Re: Assumptions are not wild guesses
We can observe that daughter element does not leave certain crystals, such as Pb in zircons

We observe that uranium and thorium are relatively plentiful in zircons, whereas lead is only present in minuscule quantities at solidification, and we understand why. Lead doesn't substitute in the lattice and is too big to fit inside. Uranium and thorium substitute nicely for zirconium.

But that means all the lead is radiogenic and is in a place where it does not fit, is not bonded, and is in a damaged portion of the crystal. Lead loss is possible and is by far the most common alteration.

The good news is that the method detects lead loss, and often produces a valid date anyway. And geochronologists have developed methods for locating unalterd7samples samples samples.


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JonF
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Message 48 of 222 (798958)
02-06-2017 5:41 PM
Reply to: Message 45 by Coyote
02-06-2017 2:37 PM


Re: Assumptions are not wild guesses
constant decay rate is a good assumption, well supported by the evidence. Only a few creationists disagree based entirely on non-scientific beliefs

I prefer "premise" to "assumption". As you know "well supported" is an understatement.

Edited by Adminnemooseus, : Fix quote box.


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JonF
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Member Rating: 2.3


(3)
Message 50 of 222 (799005)
02-06-2017 8:38 PM
Reply to: Message 49 by Modulous
02-06-2017 7:23 PM


Re: Assumptions are not wild guesses
Yeah, but here you aren't communicating with people who realize that "assumption" is not synonymous with "wild-ass guess".

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JonF
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Message 70 of 222 (827317)
01-22-2018 3:57 PM
Reply to: Message 67 by edge
01-21-2018 10:25 PM


Re: Questions
The assumptions are the the system is closed, the original isotopic composition can be estimated, the decay rates have been very nearly constant

I prefer "premises" to "assumptions" since the latter connotes lack of solid foundation.

The system is rarely assumed closed. Isochron methods indicate if the system has been open and fails to produce a date. Ar-Ar and U-Pb (the two by far the most widely used) also indicate if the system has been opened and often produce a valid date anyway.

Isochron methods produce the original isotopic composition and a date as part of the method. In Ar-Ar the original isotopic composition seldom affects the date. In U-Pb (almost always on zircons) the crystallization process readily incorporates Uranium and strongly rejects lead so the original ratio of lead to Uranium is always zero or infinitesimal.

The absolute constancy of the decay rates of relevant isotopes under terrestrial conditions is as well established as the atomic constituents of a water molecule. The processes that govern decay are fundamental to the operation of the Universe, and changes would leave unmistakable traces in an astonishing number of places. We've looked; they aren't there. http://www.talkorigins.org/origins/postmonth/oct01.html, http://www.talkorigins.org/origins/postmonth/aug06.html.


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JonF
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Message 72 of 222 (827319)
01-22-2018 4:11 PM
Reply to: Message 68 by LamarkNewAge
01-21-2018 10:56 PM


Re: Questions
Wow, what a load of horses**t! The KBS Tuff story is much more complex than that. Some dates were discarded, all for explicit and objective explanations of why they were incorrect. That's the real standard practice; nobody discards data without stating an objective reason. IIRC the initial range of dates was significantly smaller.

I wrote more at Message 5

Edited by JonF, : No reason given.


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JonF
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Joined: 06-23-2003
Member Rating: 2.3


Message 93 of 222 (827359)
01-23-2018 9:12 AM
Reply to: Message 78 by DOCJ
01-23-2018 5:27 AM


Re: Questions
Wowsers, another Electirc Universe nut!

Which has nothing to do with dating.

If you want to understand: Radiometric Dating: A Christian Perspective

If you are just blathering and have no interest in the answers: carry on as you were.

Edited by JonF, : No reason given.


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JonF
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Message 94 of 222 (827360)
01-23-2018 9:20 AM
Reply to: Message 92 by DOCJ
01-23-2018 9:00 AM


Re: Questions
. The dispute is within the scientific community

Link 1: Electric Universe nuttery. Not the scientific community.

Link 2: Thunderbolts forum: Oh, I been there. More Electric Universe nuttery. Not the scientific community.

Link 3: An Electric Universe nuttery video. Not the scientific community.

Got the stones to visit http://dealingwithcreationisminastronomy.bl.../...20Universe? Didn't think so.

Edited by JonF, : No reason given.


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JonF
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Posts: 5950
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Message 114 of 222 (827386)
01-23-2018 12:58 PM
Reply to: Message 100 by DOCJ
01-23-2018 10:52 AM


Re: Questions
Most amusing. You tell us that just saying something is scientific doesn't make it true, and two messages later you say no more than your delusions are scientific.

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JonF
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Joined: 06-23-2003
Member Rating: 2.3


Message 141 of 222 (827418)
01-23-2018 5:43 PM
Reply to: Message 132 by DOCJ
01-23-2018 3:54 PM


Re: Questions
Well, then, no problem. By your definition EU loons aren't doing science.

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JonF
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Message 142 of 222 (827419)
01-23-2018 5:45 PM
Reply to: Message 135 by DOCJ
01-23-2018 5:03 PM


Re: Questions
Not done until you successfully address the objections.

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JonF
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Posts: 5950
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Message 197 of 222 (827674)
01-29-2018 12:34 PM
Reply to: Message 194 by DOCJ
01-29-2018 9:55 AM


Re: Questions and still no answers
The point is that many independent methods produce the same result. This is called "consilience" and nobody has made any credible attempt to explain it other than the obvious one; the methods are measuring real passage of time.

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JonF
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Member Rating: 2.3


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Message 201 of 222 (827685)
01-29-2018 2:11 PM
Reply to: Message 198 by DOCJ
01-29-2018 1:39 PM


Re: Questions and still no answers
Get back to us when you have an explanation for consilience.

You are obviously hampered by your abysmal ignorance of the subject of radiometric dating. Carbon dating uses a method that is not useful for any other type of dating. There are many different and independent radiometric methods used in various situations.

Of course you are ignoring the fact that many of the methods used to make the calibration graph RAZD posted do not involve radioactivity.

Many independent methods all produce the same answer. That's an astonishing pattern of thousands of data points. It demands explanation.


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JonF
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Message 210 of 222 (827723)
01-30-2018 6:49 PM
Reply to: Message 208 by Percy
01-30-2018 1:58 PM


Re: Questions
I feel compelled to comment on knowing the initial isotopic state of the sample. Several modern methods do require that be known but the laws of physics give us the information we need. The most widely used is, of course, the aforementioned knowledge that zircons readily incorporate uranium and strongly reject lead so the initial P/U ratio is essentially zero. Another is the fact that uranium is somewhat soluble in water and thorium is not, so corals and speleothems and bones in groundwater and whatnot start with a Th/U ratio of zero. That's disequilibrium dating... think Hezekiah's tunnel.

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