Subject: Zircon Crystals and Geologic Columns
Date: Thu, 11 May 2000 18:58:44 -0700 (PDT)
From: Tim Thompson
To: do_while@ridgecrest.ca.us
With reference to the page on "Zircon Crystals and Geologic Columns",
in "Science aginst Evolution" ...
http://scienceagainstevolution.info/v4i7e2.htm
You take quite a bit of effort at refuting "my" arguments. However,
the arguments are not mine, and the use of my name in that context
is incorrect. The comments that Glenn cites come from a web page
linked to one of mine, most likely my Radiometric Dating Resource
List ...
http://www.geocities.com/Tim_J_Thompson/radiometric.html
Perhaps it would be proper to exchange my name in the comments for
a reference to the unknown author of Glenn's target page; there are
quite a number of links from my page, and I don't know which it is.
However, not being terribly shy about such things, I will give you
some reason for using my name in vain by pointing out that your
criticisms of Glenn's object of curiosity contain rather several
flaws, which I shall elucidate. For instance ...
> Apparently Tim Thompson believes that all lead is the result of
> radioactive decay. This is his fundamental error. Some lead has
> always been lead.
I don't in fact believe any such thing, and neither does anyone
else. However, I do happen to know how to tell one lead from the
other, as would any physicist of sufficient erudition. Naturally
occurring lead comes with a particular distribution of stable isotope
ratios (which means that none of those listed here are radioactive).
Isotope Relative Abundance
------- ------------------
208 52.4%
207 22.1%
206 24.1%
204 1.4%
The final product of the Uranium 238 decay chain is Lead 206, which
as you can see from the table, makes up about 24% of any natural
Lead sample. If I find a sample that is 50% isotope 206 instead,
then it's a good bet that there used to be some U-238 laying
around that has since turned into Pb-206. Furthermore, the excess
above 24% tells me how much U-238 there was. U-238 also produces
Pb-210 along the way, but it has a half-life of 22.6 years, and so
won't hang around for long.
> Since one doesn't know how much of the lead was lead to begin with,
> and how much came from the decay of uranium, one can't tell how old
> the rock is from the ratio. In all likelihood, the amount of lead
> from radioactive decay is negligible compared to the amount of lead
> in the rock to begin with.
Not true. From the explanation above, you can see that a radiogenic
history will skew the relative abundance of isotope 206 relative to
the other isotopes, which are not decay products. On an atom-by-atom
basis, we cannot tell which ones were there to begin with, and which
came from the decay of U-238. However, we do know that the excess above
about 24% indicates how much was added (in bulk) by U-238 decay. That
will tell us how much U-238 has decayed, and that related to how much
is present, and the known half life, will in principle reveal the age
of the sample.
> Where does Thompson get the idea that creationists believe that
> radioactive decay is variable?
Well, I do in fact have that idea. Curiously, I got it from a lot
of creationists telling me that they were convinced of the variability
of decay rates. I take them at their word, and presume that they do
in fact believe what they say they believe. No doubt that not all
creationists agree, but certainly many creationists do hold that view.
> Probably it comes from the list of five assumptions that evolutionists
> must make in order to use radioactive dating. (1) The initial quantities
> of mother and daughter elements is known or can be calculated. (2) No
> mother or daughter elements have been added to the sample by contamination.
> (3) No mother or daughter elements have been leeched out of the sample.
> (4) There has been enough time for a measurable amount of the mother element
> to decay to the daughter element. (5) The decay rate has been constant.
> Creationists correctly point out that not one of these five assumptions
> is unquestionably true.
Unfortunately, creationists are rarely willing to suggest under what specific
circumstances they might *not* be true, and the relevance of same to the
science of radiometric dating.
Assumption (1) is false; neither the initial abundance, nor any knowledge
of same is necessary for most radiometric dating. Specifically, the "isochron"
method was designed for just that purpose. Multi-isotope methods will also
eliminate the need for such knowledge.
Assumptions (2) & (3) are only partially true. Leeching and contamination are
like anything else in nature: They don't just "happen", they are caused to
happen by some agency or process. In many cases, perhaps most cases, one
can tell by a simple examination of the sample, whether or not it has been
exposed to a source of contamination, or a leeching agent. Both leeching
and contamination chance the chemistry and/or the isotope ratios in the
sample. That evidence in turn can tell you what happened, and maybe even
how to compensate for the effect. Assumption (4) is nonexistent. No such
assumption is made. Rather, the time period is derived from the radiometric
method, which will also reveal that not enough time has in fact passed, if
that is indeed the case. Assumption (5) is probably the only genuine
"assumption" in the list, but even here you overlook some important facts.
First & foremost, there are few known instances of variation, and all
involve electron-capture decay. In those cases the variability is on the
order of 1%, not enough to skew radiometric dating results. The theory of
quantum mechanics that governs nuclear behavior provides an explanation
for this, and no clue to any other source of variability. So, if you are
going to criticize the assumption, the criticism will be weak unless and
until you can demonstrate why it is better to assume that what we see is
what really happens, rather than assuming that what we *don't* see is
what really happens. Makes sense to me.
> The idea that radioactive decay rates don't change is believed only "in
> the backwaters of fantasyland." We would like Mr. Thompson to join us in
> Tomorrowland and learn something about atomic energy. Atomic bombs and
> nuclear power plants are not "mere flights of fantasy with no basis in fact
> or theory.
I hate to disappoint you (well, so maybe I don't all that much!). But, the
examples you give of reactors and bombs do not in fact represent any variation
in decay rate, and are therefore irrelevant. In both cases, the energy comes
from a chain reaction of neutron-induced spontaneous fission in U-235. In the
case of the bomb, the reaction is allowed to run away; in the case of the
reactor, the reaction is controlled (we hope). However, radiometric dating
involves the alpha decay of U-238, which is quite a different process. The
fission reaction leaves lots of junk behind in the form of intermediate
nuclei resulting from the symmetric (or asymmetric) splitting of the U-235
nucleus. It is very easy to tell one from the other, and so very easy to tell
whether or not this process has been effective in nature (which in fact it has,
in the natural reactors at Oklo in Gabon). Maybe it's *you* who should think
about graduating from Fantasy Land?
> Imagine what would happen if we tried to use radiometric data to determine
> the age of radioactive waste produced last year. It would appear to be millions
> of years old. Here's why ...
How about "here's why not". Again, you overlook the key role played by the relative
abundances of isotopes. Natural elements and radiogenic elements do not share the
same ratios, and it's easy to look at waste products of any age and tell right
away that they are not natural because they have heavily skewed isotope ratios,
and indeed will contain isotopes that are not natural at all, but are necessarily
decay products.
> All that heat and pressure would probably change the crystalline structure of
> the surrounding rocks, too, making them appear "metamorphic". So, if you analyzed
> the rocks near an underground nuclear test, you would find some radioactive material
> and its decay products in a ratio that would indicate that those metamorphic rocks
> were created many millions of years ago.
Not a chance. Heavy etching by high-energy particles from the blast would reveal the
true nature of events quickly, as would the effect of exposure to high gamma ray
and neutron fluxes (which would once again upset the isotope ratios).
> Thompson's claim that, "the geologic column matches perfectly the radiometric data
> at least where the columns have not been folded" is ridiculous.
The claim is in fact quite valid, and the evidence enshrined in several thousand
pages of journal reports. Perhaps you can provide a slightly better level of support
for the "ridiculous"? Perhaps you could point to a specific place, where radiometric
dating does not support the geologic column? You know, something like "at this spot
these people did radiometric dating and it didn't work". It would be, I think, more
efficacious.
And finally ...
> Whenever the sample yields the "wrong" age, the simply reject it because it was
> "obviously contaminated." That's why the (published) radiometric ages always match
> the geologic column. The ages that don't match are rejected.
That is not a true statement. That does not happen. You wish that it would happen, I
don't doubt. If it were a systematic practice, it would make you feel better about
the immorality of the opposition, sneaking fake dates. But "evolutionist" scientists
are no more liars than creationists are.
Well, I think I have said enough for now. If you are going to criticize me, you might
as well have something that really does come from me to criticize.
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Timothy J. Thompson
http://www.geocities.com/Tim_J_Thompson/
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