1. The starting conditions are known (for example, that there was no daughter isotope present at the start, or that we know how much was there).
3. Systems were closed or isolated so that no parent or daughter isotopes were lost or added.
http://noanswersingenesis.org.au/sa
rfati_radio_isotopes_watts.htm
<big>These are written by specialists and I certainly am not one.</big>
<big>Back to the K/Ar system. One complaint often raised by YECs is that there is no guarantee that the mineral being dated has remained a closed system. Such a possibility has been well understood by practitioners. It had to be overcome by those who developed the system in the first place before the technique could be used. If it was not, then scientists in all fields of historical research could not make sense of any date they were given, and the point is that the dates do make sense. They tie in with the pre-existing relative dating systems. They tie in with pre-existing knowledge. Thus, in a relative system, if one stratum was deemed to be older than another, the K/Ar system dates that way as well. If the system was as leaky as YECs make out, then why should that be the case? K/Ar systems also tie in with the pre-existing "absolute" dates. Early geologists did have some idea of the immensity of geologic time and how old some strata could be. K/Ar dating confirmed these notions. K/Ar systems support and are supported by other absolute systems that rely, in the main, on different assumptions. Thus, cross checking can often be performed to ensure the reliability of a date. Again, if the system was as leaky as YECs pretend, it is hard to see how cross checking could be performed. Finally, many YEC suggestions of a leaky system can be checked. Two assumptions often attacked by creationists are -</big>
<big>i) knowledge of the initial daughter and </big>
<big>ii) that the rock remained a closed system. </big>
<big>One way such objections are met is by the use of isochron diagrams. These are constructed from the analysis of several different minerals in a rock where the minerals contain different amounts of parent and daughter isotopes. Ratios of parent and daughter isotopes relative to a third, closely related isotope are used to obtain straight line plots, the slope of which supplies the age of the mineral and the y-intercept, the initial daughter. Hence, the initial daughter quantity is not needed with this method. The linear plot virtually ensures that a closed system has been dated. Problems which can give rise to false isochrons are well known. These problems are rare and certainly do not invalidate the system. Rather they supply dates for subsequent metamorphic events or dates between original rock formation and subsequent metamorphic events. Such dates run into tens of millions of years to hundreds of millions of years.</big>
<big>Compositions of minerals from as wide a variety of sources as possible (e.g. other planetary bodies, various terrestrial locations, etc.), are examined. This is done to ensure that a mineral from one location behaves the same as a mineral from another. If different behaviours are found then this does not invalidate a dating system. Reasons for the behaviours are found. The behaviours are researched and understood, and this new knowledge then places more constraints on the technique. Constraining a method does not make it suspect. Quite naturally it makes it more reliable. This research is not necessarily done as a part of geochronology studies either. Petrologists who wish to understand the nature of rocks undertake such research and obviously it has nothing to do with dating studies. Thus a body of literature was in existence well before radio isotope systems were developed. There was an expertise which physicists could tap into as they developed the absolute dating systems. </big>
<big>How do scientists determine the ability of minerals to retain various elements? There are many books available which describe the extent to which scientists go to determine how various minerals retain elements, under what conditions they can be contaminated, etc. Henry Faul, in his book "Ages of Rocks, Planets, and Stars" describes a lot of this. Consider the loss of argon. Minerals vary greatly in their ability to hold argon. (Hence some will be totally unsuitable for dating purposes and geologists will not use them). An advantage of argon being a gas is that, while it can diffuse through minerals, it is also easy to collect during the dating process. Not only do scientists test minerals for argon retention in the lab, but they test retention in the field as well. In the lab, a mineral is placed in a vacuum and gradually heated. All this time, the argon which has escaped is measured. Some mica's for instance lose very little argon up to a fairly high temperature, then lose a lot, rapidly, until settling down to no loss from then on. Other minerals can be shown to follow a similar pattern. To check these lab tests against reality, scientists go into the field and look for systems where once molten rock has intruded into surrounding cold rock. They can look at the increasing ages of samples taken further from the contact zone and this reinforces and refines laboratory studies.</big>
<big>Petrologists, over the years, have classified rocks and built up an extensive amount of knowledge concerning them – their compositions, physical, chemical, mineralogical; their physical and chemical structures; their properties. Ratios of elements, mineral stabilities, resistances to attack are all known with varying degrees of reliability.</big>
<big>Geologists recognise that rocks, once set, could easily undergo later metamorphic events that interfere with subsequent dating. Tests are done to check for this. For example, metamorphosis is likely to affect different minerals in different ways. Therefore, if different dating systems yield compatible ages, one can be confident that a real age has been determined. Properties of various minerals can be used to see if a rock has undergone metamorphosis. If so, different interpretations have to be placed on an associated date. For example, rather than the date reflecting the time of rock formation, it reflects the time of the last metamorphic event.</big>
<big>Scientists love a chance to test their assumptions using as many independent methods as possible. The reason for this is that scientists really would like to know what is going on in nature. They do want to know the truth. They have no hidden agendas. Conversion of souls is left up to the individual's faith. Eternal life is not tied in with how old a rock is. For that reason, many scientists are theistic including devout Christian and happily accept an ancient Earth as being reality. Therefore, testing of assumptions becomes vital to refining techniques. If the K/Ar system can be extended to other mineral types then its use can be extended. Better quality research can be done and more questions answered. Sometimes one hears YECs claim that modern dating systems were developed to give scientists time for evolution. Such claims are silly. Modern dating systems were developed largely because some people really wanted a good system for dating the earth. It had nothing to do with evolution. As I pointed out earlier, if the mainstream was so dishonest, then there are other dating systems that would put the age of the earth into trillions of years – even better still – and geologists could then use the excuse making that YECs accuse them of to deny the current systems their validity. (Returning to a theme I discussed above – YECs accuse the mainstream of guessing and making excuses. YECs rarely back such assertions up. Nevertheless, reading their literature shows that it is they who deem hand waving and just-so-stories as viable theories. Yet again the mainstream is incorrectly accused of doing precisely what YECs do.)</big>
<big>If scientists are as dishonest as Sarfati suggests, i.e. they make excuses and unsubstantiated assertions then why be limited in dishonesty when it comes to dating? By this I mean, why not claim to be able to date everything? However, the literature shows that only some things can be dated. For example, Dalrymple's book on the K/Ar system has a chapter titled "What can be dated?" Out of all possibilities only a few of the rock forming minerals can be dated. Some of these can only be dated under exceptional circumstances. Thus, biotite, a mica, can be dated in volcanic, plutonic and metamorphic rocks; lepidolite can only be dated sometimes, in plutonic rocks. Sedimentary rocks are very hard to date. The mica, glauconite, offers the only chance there. The reason for all this is that only some things are understood well enough so that scientists are confident or otherwise in the usefulness of the mineral and the technique applied to it in order to extract a date. As an example, biotite retains argon well. However, if heated above a few hundred degrees Centigrade, the mineral easily loses argon. Because of this though, the mineral, while good for providing rock formation ages, is also very useful for indicating post formation heating events. Under this scenario, a date of 50,000,000 years would not be the age of the rock. Rather it would be the age since the rock was last heated to above a few hundred degrees. And this would have to be less than the age of the rock! Quartz though is different. While it retains argon well it has a very low potassium content which makes its usefulness very limited. Understand the system and it can be used. If geologists and physicists adopted the YEC scientific method, then the mainstream could claim that everything can be dated and use statements such as "God would have" and "God could have" to answer any objections that the associated dates were based on unknown, untested and unscientific methodologies. Unless such statements are based on real knowledge of God's intentions, then really, they are all unsubstantiated assertions and as such just one of many things God could have or would have done.</big>
<big>It is important to see what is being suggested by YECs when they raise their objections. </big>
<big>1) When you read YEC literature, the impression is made that geologists are being untruthful or are blind. Either they know that the systems are leaky and ignore it or they are blissfully unaware of the potential for error. Nothing could be further from the truth. Reading the historical literature on this, you will see that scientists always raised objections to dating systems that they considered unreliable. Such dating systems could be used – but only as a last resort, in the absence of anything better. In order to develop the modern systems, something had to be offered that could answer the objections to the older systems. From the literature it is also clear that scientists love to check and cross check their systems. Thus, when tree ring dating systems matured, they were used to check the carbon 14 dating system. And sure enough, as the carbon dates went back in time, so their accuracy began to decline. The sources of these small inaccuracies are now understood and tree rings have been used to re-calibrate the carbon clock. (And the earth sure ain't 6,000 years old.)</big>
<big>2) In challenging the mainstream, YECs rarely mention their own assumptions and with good reason. Often their assumptions are groundless, cases of special pleading or contrivances. YEC critiques of an ancient Earth rely on the assumption that all dating techniques must fail in a methodological way so that any age above 6,000 years, no matter how well established, can be discounted. Assumptions behind their special pleading are rarely stated and never supported. They are merely hand waved into the story. Thus, Woodmorappe (below) can assume that decay in an ionised state is relevant to modern dating systems by assuming that God behaved in a particular way at creation, to ensure that rocks had the right amount of elements (but not all rocks mind you) so that geologists could be misled. Not only does Woodmorappe assume this for one dating system but the implication is, (and why not?) that God tweaked all other dating systems as well – but in different ways.</big>
<big>Now for some examples of YEC science. These examples are from a series of letters I posted to AiG concerning articles on dating that were written in their family magazine, Creation, and their technical magazine, TJ.
</big>
2. Decay rates have always been constant.
http://www.talkorigins.org/origins/
postmonth/mar01.html
Robert Carroll wrote:
>
> "Sverker Johansson" <lsj@hlk.no.hj.spam.se> wrote in message news:3ABF147C.A7391DD5@hlk.no.hj.spam.se...
>
> > Robert Carroll wrote:
> >
> > > "James R. Hofmann" wrote in message news:3ABB8556.74FBDB89@fullerton.edu...
> > > > Any comments on this AIG article on altered decay rates? It postulates
> > > > (very) different conditions in order for the rate involved to be
> > > > different, but it probably will get a lot of publicity.
> > > >
> > > > http://www.answersingenesis.org/doc
s2001/0321acc_beta_decay.asp
> > > >
> > > The argument seems to be that the electron cloud surrounding a nucleus
> > > would provide a strong electromagnetic barrier to a beta particle being
> > > ejected from the nucleus.
> >
> > Not quite. The nucleus itself has an electric field which holds on
> > to electrons around it. With the full complement of normal electrons,
> > there is no room for the new beta-decay electron near the nucleus,
> > so the decay process has to supply enough energy to boost the electron
> > out from the field of the nucleus. If there are no electrons in the
> > K shell, then the decay process only needs enough energy to get an
> > electron from the nucleus into the K shell, which can be significantly
> > less.
>
> Right. I was overlooking nuclear charge. This seems to be the inverse of
> K-electron capture. I'm surprised at the large changes in decay rate,
> though.
You're right, this process is in fact very like K-capture, but time-reversed, and with all of the other atomic electrons removed from the picture.
The argument presented in the article is simply bizarre. Anyone who reads it for very long does so at the risk of suffering severe brain damage. It contains confusion at near toxic levels. In my opinion a quite careful effort has been made here to misdirect the reader, and there is an implicit assumption that the readers will be unsophisticated.
The factor of 10<sup>9</sup> enhancement of the decay rate in fully stripped <sup>187</sup>Re is indeed extremely surprising on the face of it. I was surprised to hear of that myself. But it's important to remember that the decay of <sup>187</sup>Re is not really a very typical beta decay. More on this later.
The first hint that something quite special is up and that the author is attempting to mislead you about it, even if you didn't know anything at all about the physics of beta decay, is provided by Woodmorappe himself, when he refers to the <sup>163</sup>Dy system, which is stable as a neutral atom, but has been observed to decay to <sup>163</sup>Ho quite quickly when it is fully stripped. Why doesn't Woodmorappe point out that this is an incredible enhancement of the beta decay rate by a factor of infinity? Isn't that a much more spectacular effect than a mere nine orders of magnitude?
Woodmorappe doesn't want you to think about this question for too long, so he doesn't make it a central point. He wants you just to believe that all beta decays will be affected in just this way by stripping, and he later suggests that the variation probably might extend to alpha decays as well. This is why he first goes so far as to provide a spurious explanation for the broad phenomenology of beta decay lifetimes.
In the mind of any physicist who has ever calculated a nuclear beta decay, a partial explanation for the effect would already be forming or would be fully formed already, by the time that Woodmorappe mentions <sup>163</sup>Dy.
K-electrons, beta decay electrons, and any other electrons which find themselves deep inside multi-electron atoms do in fact all have a `barrier' to being excited to higher energy levels. But one doesn't generally talk about a barrier in this case, because the actual potential for electrons doesn't have a barrier. It is a purely attractive potential, with close to a 1/r dependence right up to the edge of the nucleus, changing over to an r<sup>2</sup> dependence in the region of constant charge density inside.
Remember that this is a beta decay: it is essentially a weak process resulting from a zero range interaction. It is very different from an alpha decay, in which the competition between the long range repulsive Coulomb forces inside the nucleus and the attractive short range strong interactions produce an actual barrier that an alpha particle must penetrate in order to escape from the nucleus.
Repeating it once more, all of the electrons feel the attractive Coulomb force from the nucleus, corrected by screening due to other electrons, and the repulsion of the other electrons. The Pauli principle operates, so that an inner electron cannot be excited to any of the occupied levels above it. All but the very highest levels in a multi-electron atom, in its ground state, are filled with the maximum possible number of electrons: no more electrons can be put into these states. To be excited, any electron must be given energy sufficient to get above the Fermi level in the atom. To within a few eV, the Fermi level will coincide with the continuum. At least enough energy must be given to a decay electron then, that it can reach an unoccupied bound state in the new atom (which has one more unit of positive charge on its nucleus), otherwise the decay will be energetically forbidden. In most beta decays, much more than this amount of energy is available.
Coulomb corrections to the electron wavefunction are always present when calculating beta decays, but though they are certainly substantial in certain regions of phase space, they are not generally responsible for such spectacular effects as are seen here.
But the account Woodmorappe gives of the mechanisms is not to be taken seriously. One can safely ignore what little he writes about the details. Here is a choice expository passage in which he beautifully illustrates his willful ignorance of the subject:
"This acceleration can occur under beta (negatron) decay. During b decay itself, a neutron changes into a proton, electron and electron-antineutrino, and the electron is expelled as a negative beta particle (b- - often written without the negative sign, but sometimes it is necessary to distinguish it from the rarer positive beta or positron decay b+). Because of the fact that the protons in the nucleus and the b particles have opposite charges, they attract each other, and the b- must therefore acquire sufficient kinetic energy to overcome this attraction in order to escape the nucleus. This has been likened to a particle having sufficient energy to crash through the walls of a well.2 In some b- emitters, the successful escape of a b-particle into the continuum is a relatively infrequent occurrence - hence the inferred long half-life of the nuclide."
Not to put to fine a point on it, but at this point the discussion is already complete crap. It is true in all the incidental details, but it is all essentially irrelevant. After this point the discussion in the article degenerates even further. Do not even try to learn about beta decay from this man.
I think his rather clear suggestion, here, is that beta decay electrons are somehow held inside the nucleus by the Coulomb force, that otherwise they would easily escape, and that that is the root cause of certain very long predicted and observed, rather than `inferred' beta decay lifetimes.
What he says is completely backwards. He pretends that the special case is the general case, he says nothing useful about the underlying mechanisms, and he is wrong in all of his conclusions as well as his subsequent mis-application of the ideas to radioactive dating of rocks.
In the great majority of neutral atom beta decays one can do reasonably well by ignoring the Coulomb attraction of the nucleus for the decay electron, as well as the repulsion of the atomic electrons for the decay electron. These are usually small corrections to the process, because the energy available from the change of the nuclear state, which always occurs in a weak nuclear decay, is generally much larger than the change in the atomic binding energy. Known beta decays have endpoint energies a wide range: but most typically these fall between a few hundred and several thousands of keV. `Crashing through the walls of a well' is just not an issue for the electrons emitted in beta decays.
The decay electron is almost always simply emitted into the continuum, and the chance of capture into an atomic bound state is very small. The Pauli principle forbids the decay electron from being captured into a deeply bound state of a multi-electron atom, since the inner orbitals generally remain fully occupied in the daughter atom. This statement is almost always true despite corrections for non-orthogonality of the atomic wave-functions in the daughter atom, due to the change of the nuclear charge. Capture into an outer orbital is generally quite strongly suppressed due to the weak binding of outer electrons and the small wavefunction overlap with the decay electron.
It might be worth pointing out a few more simple facts about the phenomenology and the theory of beta decay. Beta decay is in the present context treatable theoretically as if it resulted from a zero-range, current-current interaction, which transforms a proton (neutron) bound within a nucleus into a neutron (proton), with the simultaneous creation or absorption of an electron (positron) and a neutrino (anti-neutrino). The naturally occurring nuclear beta decays were very early on shown experimentally to be directly associated with transitions between discrete stationary states of the parent and the daughter nucleus, most usually a transition from the ground state of the parent to the ground state or a low lying excited state of the daughter.
Depending on the details of the nuclear structure, such a process may or may not require a large rearrangement of the nuclear state, and may or may not release a lot of energy. If the only change required in the nuclear state is a change in the charge state, or equivalently, the z-component of the isospin, and a readjustment of the nuclear well due to the change in nuclear Coulomb energy, the transition is generally called super-allowed. Such transitions are the most favoured possible beta decays, and they typically have small lifetimes, once one corrects for the basic underlying energy dependence of weak decays.
This energy dependence, by the way, is very strong. For large enough total decay energies, the dependence is roughly as (W<sub>0</sub>)<sup>5</sup> where W<sub>0</sub> is the endpoint electron energy.
The premier example of a super-allowed beta decay is of course the decay of the neutron in free space into the proton, with a lifetime of about 1000 seconds. Superallowed decays fall into a group with the lowest possible (ft) values. Actually one really discusses log<sub>10</sub> (ft), where t is the half-life and f is a theoretical factor which corrects for the widely differing total energies of nuclear beta decays.
The real explanations for sometimes very long beta decay half-lives which are predicted by theory and observed in nature (not `inferred') in quite a few naturally occurring, neutral, beta unstable atoms is that these atoms can now be seen to fall into two general classes. The classes are not mutually exclusive.
The first class includes those decays where the nuclear matrix element is large or at least not unusually small, but there is simply not very much energy available for the decay.
The second class includes cases in which the nuclear matrix element for the transition is extremely small, though there may or may not be ample energy available.
The first class includes certain allowed (as opposed to super-allowed) transitions, as well as some so-called forbidden transitions of various orders. Allowed transitions are those which can still occur when the spatial dependence of the electron and neutrino wavefunctions across the nucleus is ignored. To within about 1 percent, this is actually a good first approximation in most beta decays. Other transitions for which we must look to higher orders in the expansion of the wavefunctions are suppressed by additional factors on the order of 100, and are these are thus called forbidden transitions. The order of forbiddenness is related to the order in the expansion of the electron wavefunction in powers of the momentum at which the first contributions to the decay are obtained.
Selection rules for the allowed decays are Delta-J = 0 with no change of parity for so-called Fermi or vector transitions, and Delta-J=0,1 with no change of parity for Gamow-Teller transitions. Transitions with higher Delta-J or a change of parity are always first or higher order forbidden.
The total energy available for this beta decay which Woodmorappe concentrates on is tiny. It is the decay of the 5/2+ ground state of neutral <sup>187</sup>Re to the 1/2- ground state of 187 Osmium with an endpoint energy of W<sub>0</sub> = 2.6 keV. This decay is a so-called unique (meaning only one operator in the expansion connects the two nuclear states) first forbidden transition. The Delta-J is 2, and there is a change of parity. These factors together account for the very long lifetime of the neutral atom.
Just above the ground state in 187 Osmium, at only 9.75 keV, lies the 3/2- first excited state. Decay to this state from 187 Rhenium, if possible, would still be a first forbidden transition, but because Delta-J is only 1, it is a non-unique first forbidden transition, which is somewhat more favoured than a unique one. However decay to this state is not even a possibility in the neutral system at normal temperatures: it is energetically forbidden.
Now, the critical point to understand here is that in a very large atom, like Rhenium or Osmium, the total Coulomb binding of the atomic electrons is not at all a small number. It is especially not a small number in comparison to the tiny endpoint energy of this particular beta decay. The total electronic binding is in fact on the order of 400-500 keV. In addition, the binding is about 20 keV larger in Osmium than it is in Rhenium, due to the extra unit of nuclear charge. It's not very hard to make rough estimates of these numbers knowing just a very little about atomic physics.
Furthermore, the binding of a K-electron in these systems is approaching 90 keV in the stripped, hydrogen-like atom, though in the neutral atom it will be somewhat less due to screening from the second K-electron. So if we apply our normal intuition about beta decays here to estimate what might happen to the lifetime of the system when 75 bound atomic electrons have been stripped away and say confidently, nothing much at all, we will be sunk. The nuclear energy levels have been shifted relative to each other by a considerable amount and the energetics of the decay clearly has to be reconsidered.
In the end, the transition to the 3/2- first excited state with a bound K-electron becomes energetically allowed, and that is the dominant decay mode for the stripped system. There is much more energy available for the decay: about 60 keV versus 2 keV in the neutral system, and that, together with the increased overlap due to the smaller change in J is quite sufficient to account for 9 orders of magnitude enhancement of the decay rate. Beta decay into the continuum, interestingly, is not even energetically allowed in the stripped atom.
So we see that the systems for which this sort of thing is a very important effect are quite special. To find them, one must comb through hundreds of known beta decays, and come up with the few that have happen to have small Q values, which are comparable to the changes in atomic Coulomb binding when going from stripped or highly ionized atom to neutral atom.
The general rule, however, is approximately this: for the most part, nothing extremely spectacular will happen to total beta decay rates of most beta unstable atoms (electron emitters), even if the atoms are totally stripped. Moreover, because of the nature of quantum mechanics in a coulomb potential, it will be necessary to nearly completely strip the atoms in most cases, to be able to see any effect at all. Eliminating a valence electron will simply not be enough, and that is all that can be achieved at any reasonable temperature.
It is interesting that Woodmorappe completely omits any discussion in this article of the case of Potassium 40, which is unstable against positron emission, K-capture, to Argon 40 and by electron emission to Calcium 40. This is the relevant system in the well known Potassium-Argon dating technique. The dominant decay mode for the positron emission here is a third forbidden Delta-J=4 transition, with a change of parity. The total decay lifetime of the branch to Argon is about 1.28 billion years. The available energy is however, much larger, the endpoint being W<sub>0</sub> ~= 1320 keV. The effect of completely stripping the atoms on the decay rate in this system, though certainly different from zero, will be far less than it was in Rhenium.
The same applies to yet another case, and I wonder even more why Woodmorappe has ignored this one. Consider the odd-odd nucleus 186 Rhenium, which beta decays by electron emission to the neighboring nucleus 186 Osmium. Considerations of atomic binding energies are very nearly the same as for the case we just went through in detail. This transition is from the 1- ground state of Rhenium 186, and has a branch of about 75% to the 0+ ground state of Osmium 186 (which, being an even-even nucleus, is much more bound than is Osmium 187). There is also a 23% branch to the first (2+) excited state of Osmium, as well as smaller branches to two higher excited states. Both transitions are first forbidden, Delta-J=1, with a parity change. The endpoint energy of the transition to the 2+ state, however, is about 930 keV, and that to the ground state is nearer to 1100 keV. Again, we can expect much more modest effects to occur when the systems are totally ionized.
I will now conclude with a few remarks on the relevance of this silly and massively dishonest article to radioactive dating and geological time scales. I am doing no more than to repeat points that others have made here, but I have added a couple of numbers, just for fun.
Large atoms as we know'em and like'em, namely at all temperatures important for questions of rock formation, can be thought of as being essentially neutral when it comes to calculating their beta decays.
It is these kinds of atoms that make up rocks, whether molten or solid, and that of course includes the rocks in Woodmorappe's head. One does not typically find Rhenium atoms in charge states like 75+. It took quite a few talented people working at a complicated and expensive facility, using an accelerator like the one at GSI, to produce a usable number of these exotic objects for their experiment. To see just how absurd the discussion Woodmorappe gives of the earth's origins actually is, it's worth making a couple of simple order of magnitude estimates.
First, the gravitational binding energy of the earth can be roughly estimated from the formula for a uniform sphere:
B = 3/5 G m<sup>2</sup> / r
Taking approximate values r=6500 km, m=6x10<sup>24</sup> kg, and G = 6.67 x 10<sup>-11</sup> m<sup>3</sup> / kg / s<sup>2</sup>, this gives:
B = 2.2 x 10<sup>36</sup> J.
This corresponds to a binding energy per unit mass of:
b = 3.7 x 10<sup>7</sup> J / kg,
or a binding energy fraction (dividing b by c<sup>2</sup>) for the earth of:
f (earth) = 4 x 10<sup>-10</sup>.
What sort of conditions are required to make 75+ the expected charge state of Rhenium? Here I am going to play very fast and loose with my estimates. If the separation energy of the first electron in Rhenium is about 9 eV, and that of the last is about 90 keV, that suggests a total binding energy of about 500 KeV for all of the electrons. To separate the last electron we thus need a temperature at least on the order of 10<sup>9</sup> K, while smaller temperatures would suffice for ionizing the rest of the outer electrons. We shall need to approach charge states of 72+, 73+ or more preferrably 74+, I'd bet, in order to see very strong effects on the beta decay lifetime. If the K-shell is completely empty in Osmium, then capture to the L-shell is energetically allowed, but it is greatly suppressed over K-capture. So perhaps T = 10<sup>8</sup> K might be sufficient. To approach this kind of temperatures in the current universe, we shall need to make a descent into the core of a supergiant star. Or perhaps we could wait around for the shock wave of a supernova explosion to hit us. So while the result discussed in the article concerning bound state beta decays of fully ionized Rhenium seems possibly to be very interesting for astrophysics, it is certainly quite irrelevant for any estimates of the age of terrestrial rocks.
To make this point a little clearer, if it isn't clear enough already, consider that the binding energy fraction for the electrons in neutral Rhenium is by my above estimate on the order of:
f (Rhenium) = (500 x 10<sup>3</sup> eV) / (187 x .938 10<sup>9</sup> eV) = 1.08 x 10<sup>-6</sup>
Thus, in the process of raising the entire planet earth to the temperature necessary to make 75+ the expected charge state for Rhenium so that it could then quickly decay into Osmium, before the earth cooled, God therefore also must have made the earth gravitationally unbound. The whole planet would simply have exploded into a cloud of plasma which would even yet be expanding into space. A cloud at this temperature, having the mass of the earth, could never have coalesced to form the earth.
Unless, of course, the hand of God squeezed the plasma back into place, or He also adjusted the gravitational coupling constant ...
Now, if one is the sort who is happy with that kind of explanation, then why should one bother vomiting forth a totally botched article on the fascinating and complex physics of exotic nuclear beta decays, in an effort to make this religious point? Why wouldn't one simply assert that it's clear that God put every single atom right into its present place, and that the angels are still pushing all of the tiny little electrons around in their classical orbits? That at least would be a much more honest statement of one's actual beliefs.
> > > If this were true, K-electrons (and other low
> > > energy electrons in multi-electron atoms) would have much the same barrier
> > > to being excited to higher energy levels,
> >
> > They do.
> >
> > > making it much more difficult to
> > > achieve that plasma that Woodmorappe referred to.
> >
> > That's why we don't have Rhenium plasmas at any Earthly conditions.
> >
> > > The reference to nuclear
> > > particles "crashing through" a potential barrier serves to illuminate the
> > > crudity of his understanding of tunneling. It is a thoroughly dishonest
> > > piece of work.
> >
> > Yes, it's dishonest, but not because the physics in it is wrong.
> > The process is well known to operate inside stars.
> > It's the application to Earthly rocks that's dishonest.
Hi Sverker. I agree with everything you've said about the physics, but I think you're being much too kind here about Woody. (Of course, that's not very kind at all when you're calling him dishonest.) He has quoted some correct results of physics, but there isn't very much in what he himself says about the physics that's correct and neither has he drawn any really correct conclusions as far as I can tell.
cheers,
- dave k.
Errata:
I hate to answer my own post, especially when people have looked kindly on it, but what I said in the following paragraph requires a minor erratum:
>It is interesting that Woodmorappe completely omits any discussion in this
>article of the case of Potassium 40, which is unstable against positron
>emission, K-capture, to Argon 40 and by electron emission to Calcium 40. This
>is the relevant system in the well known Potassium-Argon dating
>technique. The dominant decay mode for the positron emission here is a third
>forbidden Delta-J=4 transition, with a change of parity. The total decay
>lifetime of the branch to Argon is about 1.28 billion years. The available
>energy is however, much larger, the endpoint being W<sub>0</sub> ~= 1320 keV. The
>effect of completely stripping the atoms on the decay rate in this system,
>though certainly different from zero, will be far less than it was in
>Rhenium.
I should amend this discussion of the A=40, Argon-Potassium-Calcium system: I went over it a little too quickly. There are some mistakes in what I said in the paragraph above, which don't affect any overall conclusions, but which are actually interesting for evaluating Woodmorappe's article.
The lifetime I quoted here was, of course, the total decay lifetime for the neutral atom, including all of the decay modes. The branch to <sup>40</sup>Ca actually accounts for about 89% of the decays. The other 11% of the decays almost all occur by K-capture to <sup>40</sup>Ar.
The total atomic electron binding in these systems can be estimated from the values in potassium (Z=19). I estimate that the total binding of the atomic electrons here is about 15 keV, while the binding of a K-electron in the stripped atoms is about 5 keV.
The first excited state (0+) of <sup>40</sup>Ca lies well above the ground state at 3352 keV, and it can just be ignored here. The first excited state (3-) of 40 K is quite low lying at about 30 keV, but it too can safely be ignored at normal temperatures. All the decays thus occur from the ground state of Potassium 40.
The endpoint energy I quoted, 1320 keV, is that for the dominant decay mode of the (4-) ground state of neutral <sup>40</sup>K. This mode is actually electron emission to the (0+) ground state of <sup>40</sup>Ca, not positron emission to the (0+) ground state of <sup>40</sup>Ar. The difference in the atomic masses of 40 Potassium and 40 Argon is 1503 keV: so that is the total energy available for the decay which is of most interest in the dating technique.
Positron emission to the ground state is energetically allowed and does occur, but as it turns out, only rarely. K-capture to the ground state dominates positron emission to the ground state, and both of these are dominated by decays to the first excited state (2+) which is at 1460 keV. The endpoint energy for positron emission is W<sub>0</sub>=489 keV, quite a bit less than what I said. But it is not enough less that we have to worry about energy shifts due to binding of atomic electrons in going to the stripped system: these are, both relatively and absolutely speaking, far smaller than in the Rhenium-Osmium case.
On the Argon side of the diagram, I've pointed out there are two states to consider. There is the 0+ ground state, to which the Q-value in the neutral system is 1503 keV, and there is also the 2+ first excited state, which lies 1460 keV above the ground state, so with a Q-value of 43 keV. The transition to the 2+ first excited state has a smaller Delta-J and is only first forbidden. Even though the Q value is small, K-capture to this state is the dominant mode for producing Argon-40. Positron emission is energetically forbidden in the transition to the first excited state, and all decays to the ground state are strongly suppressed by the nuclear matrix elements despite the larger available energy. The first excited state then decays to the ground state by emitting a 1460 keV photon (it's an E2 transition.) There can also be various associated X-rays, internal conversions, and Auger electrons. I won't get into discussing all of these subtleties.
Considering these facts, we can see that the fully stripped system is naively expected to have the same decay lifetime, to within about 10%. The 10% change comes about because fully stripped Potassium has no K-electrons. K-capture is therefore not a possible decay mode for an isolated fully stripped Potassium atom. The widths for positron and electron emission into the continuum are not much affected, but K-capture is gone. If the atom still had one bound electron though, then the mode would still be allowed.
The conclusion would appear to be that fully stripped, isolated Potassium 40 hardly ever decays to Argon 40 at all. The decay rate should go essentially to zero, exactly the opposite of the behaviour which Woodmorappe trumpets proudly in the case of Rhenium.
Of course, under realistic and imaginable conditions, where Potassium or Rhenium could actually be fully stripped, namely in very hot neutral plasmas, we should have to also consider other reactions, such as capture of continuum electrons, as well as possibly contributions from additional low lying excited states of the various nuclei. This statement is valid for Rhenium 187 as well.
If these channels are opened up, it will likely make the total changes in production rates, at least for Potassium/Argon, rather smaller than what is naively predicted, or observed for the isolated atoms.
But these are problems of nucleosynthesis, not of radioactive dating, and that is perhaps a good place to end my erratum.
If you can understand all that-- you deserve your PhD in Geology....I sure can't.
When I read it, it sounds plausible to me, but so do John Woodmorappe's inquiries, simply by virtue that I have no expertise in this area whatsoever. SO I will just post the refuations of these points and let y'all read and make your own decisions.
Personally, I think we should all stay away from these arguements and counter arguments, simply because I assume that none of us possesses the needed knowlege to critque them either way.
For example, researchers applied posterior reasoning to the dating ofAustralopithecus ramidus fossils.[10] Most samples of basalt closest to the fossil-bearing strata give dates of about 23 Ma (Mega annum, million years) by the argon-argon method. The authors decided that was “too old,” according to their beliefs about the place of the fossils in the evolutionary grand scheme of things. So they looked at some basalt further removed from the fossils and selected 17 of 26 samples to get an acceptable maximum age of 4.4 Ma. The other nine samples again gave much older dates but the authors decided they must be contaminated and discarded them. That is how radiometric dating works. It is very much driven by the existing long-age world view that pervades academia today.
http://www.talkorigins.org/faqs/hom
s/a_piths.html
In 1950, Wilfred Le Gros Clark published a paper which definitively settled the question of whether the australopithecines were apes or not. He performed a morphological study (based on the shape and function) of teeth and jaws, since these formed most of the fossil evidence. By studying human and modern ape fossils, Le Gros Clark came up with a list of eleven consistent differences between humans and apes. Looking at A. africanus and robustus (the only australopithecine species then known), he found that they were humanlike rather than apelike in every characteristic. Judged by the same criteria, A. afarensis falls somewhere between humans and apes, and possibly closer to the apes (Johanson and Edey 1981). White et al. (1994) did not judge A. ramidus by these criteria, but it is clear that ramidus is even more chimpanzee-like than afarensis. The ramidus arm bones also display a mixture of hominid and ape characteristics.
Solly Zuckerman attempted to prove with biometrical studies (based on measurements) that the australopithecines were apes. Zuckerman lost this debate in the 1950's, and his position was abandoned by everyone else (Johanson and Edey 1981). Creationists like to quote his opinions as if they were still a scientifically acceptable viewpoint.
Charles Oxnard (1975), in a paper that is widely cited by creationists, claimed, based on his multivariate analyses, that australopithecines are no more closely related, or more similar, to humans than modern apes are. Howell et al.(1978) criticized this conclusion on a number of grounds. Oxnard's results were based on measurements of a few skeletal bones which were usually fragmentary and often poorly preserved. The measurements did not describe the complex shape of some bones, and did not distinguish between aspects which are important for understanding locomotion from those which were not. Finally, there is "an overwhelming body of evidence", based on the work of nearly 30 scientists, which contradicts Oxnard's work. These studies used a variety of techniques, including those used by Oxnard, and were based on many different body parts and joint complexes. They overwhelmingly indicate that australopithecines resemble humans more closely than the living apes.
Creationists often cite Oxnard's qualifications, and use of computers to perform his calculations, with approval. This is special pleading; many other scientists are equally qualified, and also use computers. Gish (1993) states that "[a] computer doesn't lie, [a] computer doesn't have a bias". True enough, but the results that come out of a computer are only as good as the data and assumptions that go in. In this case, the primary assumption would seem to be that Oxnard's methods are the best method of determining relationships. This seems doubtful, given some of the other unusual results of Oxnard's study (1987). For example, he places Ramapithecus as the ape closest to humans, and Sivapithecus as closely related to orang-utans, even though the two are so similar that they are now considered to be the same species of Sivapithecus.
Less controversially, Oxnard also claims that, while probably bipedal, australopithecines did not walk identically to modern humans. Creationists sometimes quote this conclusion in a highly misleading manner, saying Oxnard proved that australopithecines did not walk upright, and then adding, as an afterthought (or in Willis' (1987) case, not at all) "at least, not in the human manner".
Creationists are generally reluctant to accept that australopithecines, including Lucy, were bipedal. A statement by Weaver (1985) that "Australopithecus afarensis ... demonstrates virtually complete adaptation to upright walking" is dismissed by Willis (1987) as "a preposterous claim". Willis adds: "Many competent anthropologists have carefully examined these and other "Australopithicine" [sic] remains and concluded that Lucy could not walk upright."
Willis' evidence for this consists of a statement by Solly Zuckerman made in 1970; a 1971 statement from Richard Leakey that australopithecines "may have been knuckle-walkers", and a quote from Charles Oxnard about the relationship between humans, australopithecines and the apes. In fact, none of these quotes refer to Lucy. Two of them were made before Lucy, and A. afarensis, was even discovered (and the third was made very soon afterwards, before Lucy had been studied).
Even in 1970, Zuckerman's views had long since been largely abandoned. In what is obviously a fabrication, Willis says that Leakey "referred to Lucy as an ape who did not walk upright", three years before Lucy was discovered. Leakey was merely making a suggestion (about robust australopithecines) which he soon retracted, not stating a firm opinion, and he has since stated (1994) that Lucy "undoubtedly was a biped". Oxnard (1975; 1987) has some unorthodox opinions about the australopithecines, but the Oxnard quote supplied by Willis discusses neither bipedality nor A. afarensis. Elsewhere in the same paper that Willis refers to, Oxnard (1975) repeatedly mentions that australopithecines may have been bipedal, and he has since stated (1987) that the australopithecines, including Lucy, were bipedal.
Gish (1985) has a long discussion of the debate about Lucy's locomotion. He quotes extensively from Stern and Susman (1983), who list many apelike features of A. afarensis and argue that it spent a significant amount of time in the trees. As Gish admits, none of the scientists he mentions deny that Lucy was bipedal, but he goes on to suggest, with no evidence or support, that A. afarensis may have been no more bipedal than living apes, which are well adapted to quadrupedality and only walk on two legs for short distances. By contrast, the feet, knees, legs and pelvises of australopithecines are strongly adapted to bipedality. Gish's conclusion is strongly rejected by Stern and Susman, and, apparently, everyone else:
"That bipedality was a more fundamental part of australopithecine behavior than in any other living or extinct nonhuman primate is not in serious dispute.""... we must emphasize that in no way do we dispute the claim that terrestrial bipedality was a far more significant component of the behavior of A. afarensis than in any living nonhuman primate." (Stern, Jr. and Susman 1983)
"The most significant features for bipedalism include shortened iliac blades, lumbar curve, knees approaching midline, distal articular surface of tiba nearly perpendicular to the shaft, robust metatarsal I with expanded head, convergent hallux (big toe), and proximal foot phalanges with dorsally oriented proximal articular surfaces. (McHenry 1994)
Gish writes as if showing that A. afarensis did not "walk upright in the human manner" is all that is needed to disqualify it as a human ancestor. But there is no reason that bipedality, when it first arose, had to be identical to human bipedality; that final step could have occurred later. As Stern and Susman (1983) state:
"In our opinion A. afarensis is very close to what can be called a "missing link". It possesses a combination of traits entirely appropriate for an animal that had traveled well down the road toward full-time bipedality ..."
Creationist John Morris writes:
"From the neck down, certain clues suggested to Johanson that Lucy walked a little more erect than today's chimps. This conclusion, based on his interpretation of the partial hip bone and a knee bone, has been hotly contested by many paleoanthropologists." (Morris 1994)
Almost everything in this quote is a distortion (Johanson's and Lucy's names are about the only exceptions). "Certain clues suggested" doesn't mention that the whole find screamed "bipedality" to every qualified scientist who looked at it. "a little more erect", when everyone believes that Lucy was fully erect. "the partial hip bone and a knee bone", when Lucy included almost a complete pelvis and leg (taking mirror imaging into account, and excluding the foot). "has been hotly contested", when no reputable paleoanthropologist denies that Lucy was bipedal. The debates are about whether she was also arboreal, and about how similar the biomechanics of her locomotion was to that of humans. Given that we have most of Lucy's leg and pelvis, one has to wonder what sort of fossil evidence it would take to convince creationists of australopithecine bipedality.
To support the idea that australopithecines are just apes, Parker says:
"In their critique of the Leakeys, Johanson and White (1980) noted: 'Modern chimpanzees, by this definition [Richard Leakey's] would be classified as A. africanus.' Apes after all?" (Morris and Parker 1982)
When the paper by Johanson and White is examined, it is apparent that Parker has taken their quote out of context in a way that almost reverses its meaning. Leakey did not call A. africanus a chimp, nor did Johanson and White accuse him of doing so. They criticized Leakey's definition because it was imprecise enough to also include chimps. Of course, such a criticism only makes sense if A. africanus is not a chimp.
In 1987, creationist Tom Willis accused Donald Johanson of fraud, claiming that the skeleton known as "Lucy" consisted of bones that had been found at two sites about 2.5 km (1.5 miles) apart. Willis had actually confused two separate finds which belong to the same species. (This was in spite of the fact that a best-selling book (Johanson and Edey 1981) has photos of both fossils: AL 129-1 is a right knee, while Lucy has a right femur and a left tibia.) This was a spectacular error which could hardly have been made by anyone who had done the most elementary research, but that didn't stop many other creationists from picking up the claim and repeating it. For a full history of this claim, read the talk.origins knee-joint FAQ file (Lippard 1997).
Creationists rarely address the issue of why australopithecines have a foramen magnum at the bottom of the skull. Gish (1985) criticizes Dart's reasoning that the Taung baby walked upright, based on the position of its foramen magnum. Gish correctly states that the position of the foramen magnum is closer in juvenile apes and humans than it is in adults (in apes, it moves backwards during growth), and concludes that Dart was unjustified in analyzing this feature on a juvenile skull. This is the same criticism that Dart originally faced from scientists, but Gish fails to mention that later evidence proved Dart's analysis correct and silenced his critics.
Creationists also rarely mention australopithecine teeth. Gish says that "[Dart] pointed out the many ape-like features of the skull, but believed that some features of the skull, and particularly of the teeth, were man-like". (Note the misleading implication that the apelike features really exist, while the humanlike ones are a figment of Dart's imagination.) Gish disputes this, pointing out that the molar teeth of africanus are extremely large. What Gish does not tell readers is that this is one of the few differences between them and human teeth. When the teeth of the Taung child could be properly examined, Dart's claim was strongly confirmed, and is now generally accepted:
"In fact, though the molars were larger than is now normal, most of the teeth [of the Taung child] could have belonged to a child of today." (Campbell 1988)
The first ramidus fossils were found in the early 1990s, and published in a paper in Nature in 1994 (White, Suwa and Asfaw 1994), where they were assigned to a new species, Australopithecus ramidus. The bones consisted only of a few dental fragments and some arm bones. About 8 months later, a correction was published in Nature (White et al. 1995) reassigning the bones to a new genus, Ardipithecus, and mentioning that in late 1994 they had discovered a new lower jaw and partial skeleton of ramidus. Clearly, these new finds had strengthened their earlier suspicion that ramidus might not belong in the genus Australopithecus. In later articles, they revealed that the partial skeleton was extremely fragile, that excavation of it was proceeding extremely slowly, and that it might be a while before it was fully extracted and analyzed. That turned out to be a understatement - it has taken nearly 15 years to extract and analyze the skeleton.
The ramidus team has put the time to good use, however. As well as excavating and restoring the Ardi skeleton, they have discovered 110 ramidus fossils from at least 35 individuals. They also comprehensively searched the site where the skeleton was found collecting absolutely everything there, eventually ending up with over 150,000 specimens including pollen, plants, wood, insects, snails, birds, and animals. This huge haul allowed them to accurately reconstruct the environmental conditions of 4.4 million years ago. As was originally suggested when the first ramidus fossils were published 15 years ago, their environment was a woodland setting with small patches of forest, which seems to put paid to the earlier popular idea that human bipedality was somehow linked to the savannah environment inhabited by some of the australopithecines.
Usually significant new fossils have a paper published describing them, or perhaps two, one devoted to the fossil and one to its geological setting. In this case, the ramidus team, in a scientific tour de force, have released 11 papers simultaneously in the journal Science. These cover the fossil, various specialized aspects of its anatomy, the geology, the environment in which it lived, and its implications for the human evolution.
Ar. ramidus is considerably more primitive than the australopithecines. The skull and brain size are very small, comparable to a chimpanzee. The teeth fossils show that ramidus was omnivorous, unlike chimps which are adapted to a diet of mostly fruit, and australopithecines which were adapted to heavy chewing on abrasive foods. ramidus also has greatly reduced canine teeth in the males, compared to apes. This is important because in apes canine teeth are important weapons against other males in the social group, so the diminished canines probably indicate a significant change in the social dynamics of ramidus.
The leg and pelvis bones show only imperfect adaptation to bipedalism, compared to australopithecines. The skull is quite similar to the skull of Sahelanthropus tchadensis, known from a 6 to 7 million-year-old fossil skull nicknamed Toumai which was discovered in Chad in 2001. This raises the possibility that S. tchadensis may end up being reassigned to the genus Ardipithecus.
Ar. ramidus was quadrupedal in the trees, walking along branches using the palms of their hands, as many monkeys do. (i.e. they weren't hanging from branches or climbing with a vertical torso like modern apes do). It is also claimed by its discoverers that ramidus was bipedal on the ground, though not nearly as well adapted to it as humans are. (This particular claim is being treated cautiously so far; a few important scientists have expressed reservations about it.) The foot of ramidus had a widely divergent big toe for grasping while climbing (like chimps), but lacks the extreme feet flexibility of chimps which allows them to mold their feet around objects. ramidus also has none of the anatomical specializations of chimps for knucklewalking when on the ground.
The Ar. ramidus pelvis was very ape-like in the lower pelvis, but had changes in the upper pelvis which made it an effective upright walker. It is more primitive than the pelvis of australopithecines, which were almost fully adapted to bipedality.
What is all the talk in headlines about Ar. ramidus refuting the idea of a missing link? Although it is true that no-one claims humans evolved from chimps, there is still a general perception that the last common ancestor of humans and chimps was, if not a chimp, at least somewhat chimp-like (hence the idea of a 'missing link' between chimps and humans). This ramidus skeleton disproves that, according to the discoverers. As we consider modern humans, H. erectus, H. habilis, australopithecines and ramidus, their skeletons become less and less like modern humans, but they are not becoming more and more chimp-like. Au. ramidus lacks almost all of the advanced specializations of modern chimps such as knuckle-walking and brachiation. The hands and feet of ramidus, and possibly our common ancestor with chimps, seem to have been relatively unspecialized, and in some ways more similar to our hands and feet than to those of chimps.
There was one quote from the Institute for Creation Research which I thought interesting:
There is still no solid evidence to support the fanciful idea that humans evolved from primates. This stands to reason, since mankind was specially created from the beginning.
That sums up the usual creationist attitude: evidence is irrelevant. No fossil can possibly be evidence for human evolution, no matter what it looks like, because they already know that evolution didn't happen.
Gibbons, A. (2009): A new kind of ancestor: Ardipithecus unveiled. Nature, 326:36-40.
How Humanlike Was "Ardi"? Katherine Harmon, Scientific American
White T.D., Asfaw B, Beyene Y., Haile-Selassie Y., Lovejoy C.O., Suwa G., WoldeGabriel G. (2009): Australopithecus ramidus and the paleobiology of early hominids. Science, 326:75-86.
White T.D., Suwa G., and Asfaw B. (1994): Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia. Nature, 371:306-12.
White T.D., Suwa G., and Asfaw B. (1995): Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia. Nature, 371:306-12.
