RADIONUCLIDE DATING IS RIGOROUS

Incl. intelligent design, belief in divine creation

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Re: RADIONUCLIDE DATING IS RIGOROUS

#201  Postby Weaver » Feb 25, 2016 5:37 am

That and the whole I don't have to back up my assertions with relevant citations and explanations if I just tell someone else to figure it all out based on some generic stuff spanning a couple of centuries.
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Re: RADIONUCLIDE DATING IS RIGOROUS

#202  Postby Hobbes Choice » Feb 25, 2016 11:57 pm

ScholasticSpastic wrote:I find that amateur psychoanalysis is the blind behind which many people like to withdraw when they're too lazy to do the necessary legwork to support their position.



I agree. But you need to read more, because its boring having to explain every thing. It's easy asking for citations, and ignore the ones I've given already. So as I said - run along and do the reading.
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Re: RADIONUCLIDE DATING IS RIGOROUS

#203  Postby Cito di Pense » Feb 26, 2016 12:31 pm

Hobbes Choice wrote:
ScholasticSpastic wrote:I find that amateur psychoanalysis is the blind behind which many people like to withdraw when they're too lazy to do the necessary legwork to support their position.


I agree. But you need to read more, because its boring having to explain every thing. It's easy asking for citations, and ignore the ones I've given already. So as I said - run along and do the reading.


Well, let's be clear about one thing, and it is that you don't have any cohesive objection to assessing the ages of rocks and so on by considering processes of radioactive decay. If that's the case, what are you fucking around with in this thread?

If you do have an issue with our understanding of radioactive decay series, run along and do some reading about radioactive decay processes and the cosmic abundances of the elements, and how our assessment of the heat flow budget of the planet would have to be reassessed if we had to toss out what we know about radioactive decay series.
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Translation by Elbert Hubbard: Do not take life too seriously. You're not going to get out of it alive.
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Re: RADIONUCLIDE DATING IS RIGOROUS

#204  Postby ScholasticSpastic » Feb 26, 2016 3:30 pm

Hobbes Choice wrote:<snip>But you need to read more</snip>

This is the bit of what you posted that I agree with. I think everyone needs to read more. It would be lovely if we structured our society to better reward the pursuit of knowledge rather than applying bling to our automobiles or idolizing overgrown children who are very good at playing with their balls.

However:
1) It's a dick move to make claims about how much your interlocutor knows without some sort of reasonable basis for doing so.

2) If you're not a fan of explaining things, what are you doing on a discussion forum? Either you'll know more than who you're interacting with and you'll be explaining something, or you'll know less and you'll be having something explained to you. That's just how grown-ups have conversations. Sometimes you'll think you know more, but you'll find out you're wrong. That can't happen without the explaining things part, either. Finding out you're wrong about something is awesome because it means you probably won't be as wrong about that thing later.
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Re: RADIONUCLIDE DATING IS RIGOROUS

#205  Postby skipbond » May 12, 2016 2:21 pm

Calilasseia wrote:I can think of one reason why we can find isotopes with shorter half-lives than 100 million years. They're the decay products of some of those longer-lived isotopes. That's why we find radium in coal dust - it's a decay product of uranium. Any reasonably ancient piece of rock containing uranium will also contain radium in small but measurable quantities. Since uranium percolates through geological water flows into coal seams and becomes resident in the coal in measurable quantities, radium appears in the coal as well. It's one of the reasons that ash from coal burning is a quantifiable radiological hazard. Find out more about this from this scientific paper among others. :)

Then, some of those longer-lived isotopes induce other elements alongside them to become radioactive. Neutron activation is a well-known phenomenon arising from nuclear reactors. My old favourite resource, Kaye & Laby, has a nice long article on neutron activation cross sections. Basically, what happens is this. Long-lived alpha-decay emitters such as uranium and thorium emit alpha particles (helium nuclei). In the case of 232Th, these have an energy of around 35.4 MeV, whilst those for 238U have an energy of 47.3 MeV. These can interact with other nuclei via collisions, producing an effect known as spallation, where the collision results in the liberation of a neutron or other fragment from the target nucleus. That neutron, in turn, can be absorbed by a stable nucleus, and transformed into a radioactive nucleus. For example, a stable 58Ni nucleus can absorb a spallation neutron, becoming 59Ni, which is radioactive, decaying via electron capture to the stable 59Co, with a half-life of 75,400 years.

Of course, which of the surrounding stable nuclei absorb the spallation neutron is dependent upon several factors, but this mechanism produces elements such as technetium in tiny quantities in appropriate geological strata. No isotope of technetium has a half life greater than 4.2 million years (this is an element with no stable isotopes), so its detection in a natural rock sample indicates that it was produced by neutron activation of molybdenum followed by beta decay (typically neutron activation of 98Mo to become 99Mo, which beta-decays with a half-life of 65 hours to produce 99Tc, which has a half-life of 211,000 years. Other technetium isotopes are produced by spontaneous fission of uranium, such as that occurring in the Oklo natural nuclear reactor.

Incidentally, a tiny fraction of 238U nuclei can undergo spontaneous fission, not only producing elements such as technetium directly, but producing other elements via neutron activation (three neutrons are released by the fissioning nucleus). However, a comparison of the interaction cross sections shows that this is a very infrequently occurring process - the cross section for 238U fission is around 4 × 10-6 barns (which means it doesn't happen very often). Compare this with the fission cross section for 235U, which is 583 barns, or 239Pu, which is 748 barns (both are fissile materials capable of being utilised in a nuclear reactor or a nuclear weapon as a result).



Radioactive dating is claimed to prove that the earth is billions of years old, but the methods are based on a number of unprovable assumptions. For example, it is assumed that radioactive decay rates have not changed in the past. Specifically, geochronologists assume that radioactive decay rates are unaffected by physical conditions like temperature and pressure. They also assume they are independent of the chemical environment.

The atomic nucleus is extremely tiny compared with the overall size of the atom—about 100,000 times smaller in diameter. Since the nucleus is located at the centre of the atom, it is well shielded by the surrounding electrons from external physical and chemical conditions. Radioactive decay, being a nuclear process, is thus considered to be independent of external conditions. The constancy of decay rate is a foundational assumption of the whole radioactive dating methodology. Faure states:

‘ … there is no reason to doubt that the decay constants of the naturally occurring long-lived radioactive isotopes used for dating are invariant and independent of the physical and chemical conditions to which they have been subjected …’1

One of the modes of radioactive decay, electron capture, occurs when a proton in the nucleus of an atom spontaneously captures an electron from one of the shells2 and becomes a neutron.3 The mass of the atom remains the same but the atomic number decreases by one. Electron capture is the only radioactive decay mode that is recognised as possibly being affected by physical conditions such as pressure, but the effect is considered insignificant and is ignored.1

However, a recent paper about the decay of beryllium-7 (7Be) has found that, contrary to previous thinking, the chemical environment noticeably affects the half-life of radioactive decay by electron capture.4 Beryllium is a rare, hard, light metallic element in the second column of the periodic table—an alkaline earth element. Its nucleus contains four protons, and the usual stable form also contains five neutrons, and thus has a mass number of nine. There is a lighter isotope of beryllium with a mass number of seven, with only three neutrons in its nucleus. The lighter isotope is unstable and decays to Lithium-7 (7Li) by electron capture (Figure 1). The energy released in this process is mostly emitted as a gamma ray. The half life of 7Be is about 53 days.

In the recent paper, geochemist Chih-An Huh reported that the decay rate of 7Be depends on its chemical form.4 The measurements were done at the unprecedented high precision of ±0.01%, some ten times better than any reported previously. An extremely sensitive and stable spectrometer was used to monitor gamma rays from the decay of 7Be. Three different chemical forms of 7Be were measured, the hydrated Be2+ ion in solution surrounded by four water molecules ([Be(H2O)4]2+), the hydroxide (Be(OH)2), and the oxide (BeO). The measured half lives were 53.69 days, 53.42 days and 54.23 days respectively—a 1.5% variation from the shortest to the longest. The variation is much greater than previously considered.

Creationists, for many years, have disputed the billions of years from radioactive dating calculations because they conflict with the 6000-year Bible time-scale. One assumption they have challenged is the constancy of decay rates. Curiously, Richard Kerr has picked up this scepticism in his report of Huh’s findings, and makes a particular point of addressing creationists:

‘Creationists hoping to trim geologic history to biblical proportions will be disappointed—the variations seen so far are much too small, just a percent or so, to affect the Earth’s overall time scale.’5

Despite these comments, the 1.5% variation in the half-life of 7Be due to chemical environment was a surprise, and shows that the previous assumption that rates are constant is not correct. One of the most widely used geological dating methods, the radioactive decay of 40K to 40Ar, nearly always occurs by electron capture.6 The effect of chemical environment on the decay rate for 40K should be less than for 7Be because potassium has extra electrons in outer shells. These electrons would shield those inner electrons that are more vulnerable to electron capture from the external chemical environment. The important question, though, is what factors may have controlled the distribution of radioactive isotopes within the rocks of the earth.
1)Faure, G., Principles of Isotope Geology, 2nd ed., John Wiley & Sons, New York, p. 41, 1986.
2)Only from the s orbitals, because all others have nodes at the nucleus, i.e. regions of zero probability of finding an electron.
3)An electron-neutrino is also released.
4)Huh, C.-A., Dependence of the decay rate of 7Be on chemical forms, Earth and Planetary Science Letters 171:325–328, 1999.
5)Kerr, R.A., Tweaking the clock of radioactive decay, Science 286(5441):882–883.
6)Faure, Ref. 1, p. 30. .
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Re: RADIONUCLIDE DATING IS RIGOROUS

#206  Postby scott1328 » May 12, 2016 5:28 pm

what's with the quoting with no comment?
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Re: RADIONUCLIDE DATING IS RIGOROUS

#207  Postby Rumraket » May 12, 2016 6:05 pm

His 2nd quote is his comment I think.
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Re: RADIONUCLIDE DATING IS RIGOROUS

#208  Postby Shrunk » May 12, 2016 6:06 pm

scott1328 wrote:what's with the quoting with no comment?


Or citation. :naughty:
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Re: RADIONUCLIDE DATING IS RIGOROUS

#209  Postby Shrunk » May 12, 2016 6:08 pm

"A community is infinitely more brutalised by the habitual employment of punishment than it is by the occasional occurrence of crime." -Oscar Wilde
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Re: RADIONUCLIDE DATING IS RIGOROUS

#210  Postby Calilasseia » May 12, 2016 6:55 pm

It's a piece of apologetics from creation.com. First of all, the assertion that radiometric dating relies upon "unprovable assumptions" gives the game away. Except that, oh wait, the constancy of decay rates over geological time isn't an "assumption", it's been tested, with respect to such data as the observations from SN1987A, in which the decay rates observed for isotopes in the supernova remnant were observed to be the same as those today, despite the fact that the spectroscopic data indicating this took 169,000 years to reach us.

As for the assertion that Huh's paper cast doubt upon radiometric dating, this is another piece of dishonest creationist fabrication that bears no relation to the content of his actual paper. First of all, scientists proposed that electron capture could be affected by altering the electron density around the nucleus of certain isotopes over 50 years ago, but didn't have the means to verify this when the proposal was first presented. Second, the decay mode of the principal isotopes used for dating of ancient material (such as 238U, 235U, 147Sm) decay by alpha decay, which is not postulated to be affected by changes in electron density. Other isotopes such as 87Rb, decay via beta decay, again not affected by electron density. Third, a change in the decay constant for a long-lived nuclide, even if reliably detected, of the order of just 1.5%, would not be enough to force-fit a 4.6 billion year half-life into 6,000 years - a 1.5% decrease of such a half-life would reduce it from 4.6 billion years to 4.531 billion years, so such an effect would be completely useless as a device to try and force-fit the actual data to conform to fatuous mythological assertions, unless of course one was relying upon the stupidity of the audience, as is frequently the case with creationists.

Furthermore, let's take a look at what Huh actually said in his paper, shall we? The paper in question is this one:

Dependence Of The Decay Rate Of 7Be On Chemical Forms by Chin-An Huh, Earth and Planetary Science Letters, 171: 325-328 (1999) [Full paper downloadable from here]

First, in the introduction, Huh reports as follows:

Huh, 1999 wrote:1. Introduction

Beryllium-7 is the lightest radioactive nuclide that ecays by capturing an orbital electron from the innermost electron shell (1s or K-shell) at its nucleus. It was first proposed more than a half century ago that the decay rate of 7Be could be altered by changing the electron density at the nucleus [1,2]. Following this suggestion, numerous attempts were made to determine the variations of the decay rate of 7Be in various chemical forms [3–12]. However, these experiments were primarily performed 4 to 5 decades ago [3–11] and the most recent report was published in 1970 [12]. During that time period, the detection of 7Be decay was conducted using ionization chambers or NaI detectors. The reported errors for the decay rate associated with such measurement techniques were generally of the order of 0.1–1%, making it rather difficult to resolve the subtle difference of the 7Be decay rate among different combinations of Be and anions. Considering the advances in semiconductor technologies and the lack of new measurements in the past three decades, it is expedient to revisit this issue now. Using an advanced HPGe γ-spectrometry system, the decay constants of 7Be in Be2+(OH2)4, Be(OH)2 and BeO have been measured at unprecedented high precision. The experimental procedures and results are reported below.


References [1] and [2] cited above are the following papers:

Possibility Of Altering The Decay Rate Of A Radioactive Substance by E. Segré, Physical Review, 71: 274-275 (1947)

Alteration Of Radioactive Periods Of The Elements With The Aid Of Chemical Methods by R. Daudel, Reviews of Science, 85: 162 (1947)

Now it turns out that R. Daudel was pretty prolific on the subject, and also has the following paper associated with him:

The Decay Probability Of Be7 As A Function Of The Ionization Of The Atom by P. Benoist, R. Bouchez, P. Daudel, R. Daudel & A. Rogozinski, Physical Review, 76(7): 1000-1001 (October 1949)

So the idea that constancy of decay rates was an "assumption", is another of those dishonest creationist fabrications, given that scientists set out to test this as far back as 1947. But of course, you won't see any of this mentioned in duplicitous creationist apologetics.


Moving on, let's see what Huh says in the discussion section of his paper, shall we?

Huh, 1999 wrote:3. Discussion

The decay half-life of 7Be reported previously in the literature falls in the range 52.93–53.61 d ([15] and references therein), and the weighted average of 53.3 d is generally adopted in various applications using this nuclide. The uncertainties of these measurements vary from less than 0.2% (e.g., [13,16,17]) to greater than 0.5%. Therefore, error bars of these measurements do not always overlap. Because the chemical forms of Be in these measurements were often unspecified, it is not clear whether the difference is due to different chemical environments or is simply caused by experimental errors. In the present study, by measuring the decay rate of 7Be in three common forms of Be with an unprecedented high precision of ~0.01%, it was shown that the half-life of 7Be in natural environments could vary by as much as 1.5%. The variation can be explained by a change in electron density around the nucleus of Be atom due to its association with different anions, and hence different electronic polarizability and dipole moments. Besides 7Be, some other nuclides having important geochemical applications (e.g., 26Al, 36Cl, 40K, etc.) also undergo electron capture decay. Thus, decay rates of these nuclides may also depend on their chemical forms, but the effect will probably be smaller for heavier nuclides due to a better shield of K-shell electrons by more electrons and shells.


So already, Huh's paper builds on the previous work of Daudel and others in 1947, by applying modern, high-precision methods unavailable to those earlier authors, to the proposition advanced back then. Furthermore, a reason for Beryllium being most affected by this phenomenon amongst the elements thus far studied, is because it only has four electrons, and the electrostatic forces on K shell electrons are subject to virtually no shielding. Heavier elements, on the other hand, will exhibit this effect to a reduced extent precisely because of that shielding of K shell electrons. So even if we assume that the variation in decay constant for a heavier element is the same 1.5% for heavier elements, as opposed to the lesser value Huh clearly states will be the case above, then the variation in half-life for 40K, an isotope used in dating that does decay by electron capture (but, note not solely via this route), will modify the half-life thereof from 1.251 billion years to 1.232 billion years. A lesser modification of the decay constant will result in a lower reduction. Once again, the idea that this validates fatuous assertions about the universe only being 6,000 years old, is as fatuous as those assertions.
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