Age dating question
AllanL
traits in sexual reproduction; those are quite a bit of information and
it'll take some time for me to digest them. For reasons explained
previously, I have another question regarding the age dating for
objects or fossils. Now, I understand that the fact is there are
several methods for dating regarding, say, the age of the earth, or a
particular fossils, and these methods typically all agree with each
other on the results. These methods commonly involve the calculation of
measuring the amount/ratio of element A and element B, where element A
would naturally decay into B, thus by calculating the ratio and the
rate of decay, one calculate the age of the object in question.
(Ignoring the on a cosmo scale which uses other methods)
A rather popular arguement that keeps on repeating itself on various
boards is that such methods require a constant rate of decay with
knowledge of starting condition and no outside influence, etc. I saw an
analogy somewhere as follows: "A person (#1)walks into a room and
observes another person (#2) reading a book. The book opens to page 100
at the time of entrance of #1. One minute later, #2 turns the page to
101; another minute later, #2 turns the page to 102. #1 then conclude
that prior to #1 entering the room, #2 has been in the room for 99-100
minutes. Since (1) the person might not start at page 1, (2) the book
might have pages with fewer/more content and thus require fewer/more
time to read, and (3) person #2 could be distracted by #1 somehow
during the observation, or there are some circumstances to help/hinder
#2 during the reading time previously, the method cannot provide a
reasonable analysis of #2's time in the room reading."
I am trying to find a suitable counter-arguement for this.
Specifically, are there any way of determining the following to ensure
the decay-type of dating method?
1, the original composition of elements as starting condition;
2, the rate does not change over time;
3, the fact of observation and measurement, and the relevant conditions
during an object's life time, would not influence the results.
Thanks in advance.
Timberwoof
"AllanL" <darkne...@hotmail.com> wrote:
Laboratory Geiger counters have a "quiet" mode in which they don't make
tick noises, but merely advance a digital counter. They don't disturb
the radioactive atoms in the materials under test at all. ;-)
> Specifically, are there any way of determining the following to ensure
> the decay-type of dating method?
> 1, the original composition of elements as starting condition;
Physicists know an awful lot about how radioactive materials decay and
what by-products they leave behind. It is possible, by assaying the
current composition, to determine the composition at formation.
> 2, the rate does not change over time;
Constancy of natural laws is a foundation of scientific study. Now it
turns out that the physics that governs how stars shine is very closely
related to the physics that governs radioactive decay. Astronomers have
spent a lot of time examining the spectra of faraway stars and galaxies.
They clearly show that the same processes have been operating the same
way pretty much since the beginning of time.
Recent claims that the rate of radioactive decay was once higher don't
make sense: that would imply that many more elements would be naturally
radioactive. This would have caused the Earth to melt ... and, of
course, stellar physics to work very differently to begin with.
> 3, the fact of observation and measurement, and the relevant conditions
> during an object's life time, would not influence the results.
Ah, yes, a worry generated by the Heisenberg Uncertainty Principle. That
principle doesn't apply when you measure radioactivity this way. It
applies to electrons around a nucleus. There's more discussion about
this subject here:
http://en.wikipedia.org/wiki/Uncertainty_principle#The_uncertainty_princi
ple_in_popular_culture
> Thanks in advance.
--
Timberwoof <me at timberwoof dot com> http://www.timberwoof.com
Dear aunt, let's set so double the killer delete select all.
A.Carlson
wrote:
>Thanks for everyone's input on the other thread regarding mutation
>traits in sexual reproduction; those are quite a bit of information and
>it'll take some time for me to digest them. For reasons explained
>previously, I have another question regarding the age dating for
>objects or fossils. Now, I understand that the fact is there are
>several methods for dating regarding, say, the age of the earth, or a
>particular fossils, and these methods typically all agree with each
>other on the results. These methods commonly involve the calculation of
>measuring the amount/ratio of element A and element B, where element A
>would naturally decay into B, thus by calculating the ratio and the
>rate of decay, one calculate the age of the object in question.
>(Ignoring the on a cosmo scale which uses other methods)
A somewhat limited explanation. There are a few other common factors
that can make the whole process a little more complex and harder to
justify the typical Creationist's simplistic critique of this method
that they have absolutely no interest in taking seriously if it
doesn't give them the answer that they seek.
>A rather popular arguement that keeps on repeating itself on various
>boards is that such methods require a constant rate of decay with
>knowledge of starting condition and no outside influence, etc.
Independent evidence for a constant rate of decay as well as actual
knowledge or very reasonable assumptions of starting conditions exist
and are not honestly dealt with by Creationist apologetics.
Certain geological formations, for example, have pretty well
understood chemical processes that created them in which subsequent
daughter elements would not be present at the beginning.
In more complex decay relationships there are often several built in
checks and balances that are simply glossed over by Creationist
apologists. There are also a number of different independent lines of
evidence that give the same consistent answers regarding the 'age' of
particular things.
>I saw an
>analogy somewhere as follows: "A person (#1)walks into a room and
>observes another person (#2) reading a book. The book opens to page 100
>at the time of entrance of #1. One minute later, #2 turns the page to
>101; another minute later, #2 turns the page to 102. #1 then conclude
>that prior to #1 entering the room, #2 has been in the room for 99-100
>minutes. Since (1) the person might not start at page 1, (2) the book
>might have pages with fewer/more content and thus require fewer/more
>time to read, and (3) person #2 could be distracted by #1 somehow
>during the observation, or there are some circumstances to help/hinder
>#2 during the reading time previously, the method cannot provide a
>reasonable analysis of #2's time in the room reading."
Analogies are great at explaining a particular concept but they by no
means delineate or confer the same or similar restrictions on what is
being 'explained'. A may be like B in one way, and pointing this out
may be a good way to explain some characteristics of B, but that does
not mean that A must therefore be like B in every other way as well.
People who read books have free will and can start the process
anywhere they choose. In the physical world there are processes that
are essentially chain reactions, where one thing inevitably leads to
another, which itself inevitably leads to another. A well understood
process that rigidly follow the laws of physics and chemistry is
clearly not analogous to someone with free will reading a book in many
obvious ways.
One can only wonder whether certain analogies are drawn up out of
ignorance or dishonesty. For someone who does not truly understand a
process and has no real interest in doing so from the outset, the
process of rationalizing can often lead to the crafting of 'arguments'
that are misleading, whether intentional or not. Unfortunately, these
misleading arguments exist even long after the fallacy is pointed out.
>I am trying to find a suitable counter-arguement for this.
Concentrate on how A is not like B and point out to anyone using bad
analogies that they have the burden of proof to prove otherwise
outside of the analogy itself.
>Specifically, are there any way of determining the following to ensure
>the decay-type of dating method?
>1, the original composition of elements as starting condition;
This will obviously vary from composition to composition. Are we
talking about limestone? lava flows?
>2, the rate does not change over time;
That would be where both independent checks and balances as well as
alternate dating methods as well as additional lines of evidence not
even related to dating methods can come into play, at least with
respect to the overall claim that is being made.
For example, never mind the fact that dinosaur bones are invariably
dated as being 'old', you never find entire lines of modern animals
(think about most modern mammals - hardly a trivial collection) mixed
in with those of 'early' dinosaurs.
Remember that, with such arguments, the Creationist is trying to sell
the idea that all animals were created at the same time.
>3, the fact of observation and measurement, and the relevant conditions
>during an object's life time, would not influence the results.
A reasonable assumption carried to extremes by Creationist apologists
who, themselves, conveniently ignore the implications of their own
poorly crafted arguments.
>Thanks in advance.
chris.li...@gmail.com
This matters mainly in 14C dating. When dating remains on the basis of
carbon-14, geochemists do measure the ratio of carbon-12 to carbon-14.
The proportion of carbon-14 in the atmosphere at times in history is
well known, based mainly on, IIANM, ice-core samples from Greenland.
Carbon-14 dating, though, is useless for anything older than about
50,000 years, and totally useless for mineralized remains. There has to
be carbon before you can use carbon-14, right?
A much more robust method is isochron dating:
http://talkorigins.org/faqs/isochron-dating.html#isochron
Isochron dating does not rely on the initial amounts of the isotopes,
and thus is not subject to this nuisance variable. Read the FAQ- it
explains it much better than I can.
> 2, the rate does not change over time;
Is there evidence that the rate has changed at all? Say, nuclear
submarines exploding spontaneously?
> 3, the fact of observation and measurement, and the relevant conditions
> during an object's life time, would not influence the results.
Already addressed by Timberwoof: the uncertainty principle says we can
know the position of an electron, or it's vector around the nucleus,
but not both.
>
> Thanks in advance.
You're welcome. Hope it helped.
Chris
Mike Ruskai
<darkne...@hotmail.com> dribble thusly:
>A rather popular arguement that keeps on repeating itself on various
>boards is that such methods require a constant rate of decay with
>knowledge of starting condition and no outside influence, etc. I saw an
[snip]
>I am trying to find a suitable counter-arguement for this.
>Specifically, are there any way of determining the following to ensure
>the decay-type of dating method?
>1, the original composition of elements as starting condition;
>2, the rate does not change over time;
>3, the fact of observation and measurement, and the relevant conditions
>during an object's life time, would not influence the results.
>
>Thanks in advance.
The rebuttal is simple when considering carbon-14 dating. Due to its
short half-life (5730 years), it's only useful for measuring
geologically young ages.
So young, in fact, that there are many different methods of dating the
same object beyond C-14. Some are archaelogical in nature - the date
of a given artifact is known from historical records, and can be
compared with the date calculated from C-14 analysis.
My favorite cross reference, however, is dendrochronology. That's
dating using tree rings. Trees, as you are no doubt aware, create one
ring per year. The size of the ring depends on the climate conditions
of the year in question. In other words, if you look at the pattern
of rings from two different trees in the same area from the same time
period, the patterns will match. So you can start with a core from a
living tree, follow its rings back hundreds of years, until the
pattern overlaps with a core sample from a tree long since dead. That
dead tree's rings can then be followed back further, until an even
older dead tree sample is found to overlap.
Using bristlecone pine trees, which live for thousands of years, you
can get a continuous record going back almost 9,000 years.
Use C-14 dating for the oldest sample, and you get the same number,
within the degree of error that the sample size dictates.
I don't know if there are any specific examples, but it's certainly
possible to have a single artifact made of wood which can be
independently dated via archeological, dendrochronological, and
radiological means to the same age.
So the rate of decay of carbon-14 in the past has not changed, as
expected. Calculations of age based on that rate have been confirmed
via independent means.
A complete rebuttal would, of course, address the confirmation of
other unstable isotopes' decay rates. Specifically ones that measure
ages in millions or billions of years.
However, the confirmation of C-14 accuracy already brings you back
some 50,000 years, which is far older than the 6,000 year age of the
YEC's imaginary world. No one else questions the efficacy of
radiological dating, so there's little point in going further simply
as a rebuttal.
Especially since no YEC will admit being proven wrong regardless.
--
- Mike
Ignore the Python in me to send e-mail.
Nashton
This principles applies to all subatomic particles, not only electrons.
> http://en.wikipedia.org/wiki/Uncertainty_principle#The_uncertainty_princi
> ple_in_popular_culture
>
>> Thanks in advance.
>
--
Nicolas
"And, heaving alljawbreakical expressions out of Sare Isaac's universal
of specious aristmystic unsaid, A is for Anna like L is for liv."
Finnegans Wake (293)
".... It means that all living things are the product of mindless
material forces such as chemical laws, natural selection, and random
variation. So God is totally out of the picture, and humans (like
everything else) are the accidental product of a purposeless universe.
Do you wonder why a lot of people suspect that these claims go far
beyond the available evidence?" Phillip E.Johnson, The Church Of Darwin
Jon Fleming
wrote:
<snip>
>Specifically, are there any way of determining the following to ensure
>the decay-type of dating method?
>1, the original composition of elements as starting condition;
This is not problem in most methods. The issue is the amount of
"daughter product"; this is the product that is produced by
radioactive decay. How do we know how much of the amount of daughter
product that we measure was produced by radioactive decay since the
rock solidified? (The remainder being present already at
solidification or added later; for the latter case, see below). If a
rock solidified with a lot of daughter product already present and we
assumed that all the daughter product was produced by radioactive
decay after the rock solidified, we would greatly overestimate the age
of the rock. But, as I said, not a problem.
1. Isochron methods, and the Argon-Argon method, produce the initial
quantity of daughter product automatically as part of the analysis.
2. The most widely used method, the uranium-lead concordia-discordia
method, is applied only to minerals (mostly zircons) that very
strongly reject the daughter product (lead) at solidification.
Therefore the amount of daughter product we measure is automatically
due to radioactive decay after solidification. Even the creationist
RATE group acknowledges this; from "Helium Diffusion Rates Support
Accelerated Nuclear Decay" at
<http://www.icr.org/pdf/research/Helium_ICC_7-22-03.pdf>:
"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 [14,
pp. 335-337]. We emphasize 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."
3. The fairly common Potassium-Argon method involves a gaseous
daughter that easily escapes liquid magma or lava under most relevant
circumstances. Therefore it is unlikely that any significant amount
of daughter was present at solidification, assuming rational sample
selection (seldom practiced by creationists). The high rate of
agreement between this and other methods that are not subject to an
initial-daughter problem demonstrates the so-called "excess argon" is
seldom a problem.
>2, the rate does not change over time;
Some good stuff posted on this already; basically, if the rate had
changed it would leave lots of traces that we don't see. For example,
observations of the Oklo reactor are relevant, placing incredibly
small limits on the amount of difference that could have existed 1.7
billion years ago. The many astrophysical observations pretty much
seal the case.
>3, the fact of observation and measurement, and the relevant conditions
>during an object's life time, would not influence the results.
We know, beyond any shadow of a doubt, that the fact of observation
and measurement have no possible effects in this case.
If relevant atoms are gained or lost in between solidification and
measurement (for example, daughter product leached out by diffusion at
high temperature), we would get the wrong answer. But, again, not a
problem.
Isochron methods, the argon-argon method, and uranium-lead
concordia-discordia methods are essentially certain to detect when
such a problem has occurred. It is faintly possible that, once in a
great while, one of these methods misses such a problem; but, like you
winning the lottery, we know it doesn't ALWAYS happen. Therefore
almost all (if not all) of our hundreds of thousands of age
determinations are correct.
In addition, the argon-argon method and concordia-discordia methods
can often produce a valid age even when relevant atoms have been
gained or lost!
--
jrf
replace nospam with group to email
B Richardson
ISTM that radon being in the decay chain for Uranium is
inconvenient for a fast decay hypothesis. Its a mobile
gas with a half-life of 3.825 days. If the production
of it is increased by several orders of magnitude for
a short while, wouldn't it would leave a disproportionate
amount of decay product in fissures and other escape
routes for the gas during that time frame?
Jeffrey Turner
> Timberwoof wrote:
>>
>>
>> Ah, yes, a worry generated by the Heisenberg Uncertainty Principle.
>> That principle doesn't apply when you measure radioactivity this way.
>> It applies to electrons around a nucleus. There's more discussion
>> about this subject here:
>
>
> This principles applies to all subatomic particles, not only electrons.
Radioactive decay is an aggregate process, the Heisenberg Uncertainty
Principle doesn't enter into it.
--Jeff
--
Often war is waged only in order to
show valor; thus an inner dignity is
ascribed to war itself, and even some
philosophers have praised it as an
ennoblement of humanity, forgetting the
pronouncement of the Greek who said,
"War is an evil in as much as it produces
more wicked men than it takes away."
--Immanuel Kant
Dave Oldridge
@75g2000cwc.googlegroups.com:
> Thanks for everyone's input on the other thread regarding mutation
> traits in sexual reproduction; those are quite a bit of information and
> it'll take some time for me to digest them. For reasons explained
> previously, I have another question regarding the age dating for
> objects or fossils. Now, I understand that the fact is there are
> several methods for dating regarding, say, the age of the earth, or a
> particular fossils, and these methods typically all agree with each
> other on the results. These methods commonly involve the calculation of
> measuring the amount/ratio of element A and element B, where element A
> would naturally decay into B, thus by calculating the ratio and the
> rate of decay, one calculate the age of the object in question.
> (Ignoring the on a cosmo scale which uses other methods)
>
> A rather popular arguement that keeps on repeating itself on various
> boards is that such methods require a constant rate of decay with
> knowledge of starting condition and no outside influence, etc. I saw an
> analogy somewhere as follows: "A person (#1)walks into a room and
Isochron methods allow us to determine the starting condition. When a
rock is formed, the chemistry determines the ratios for each included
mineral. The ratios of interest are:
1. The ratio of radioactive element to daughter isotope.
2. The ratio of daughter isotope to non-radiogenic isotope (of the
daughter element).
1 is fixed at formation on a per mineral basis, that is it is different
for different minerals. 2 is fixed at formation across all minerals.
By measuring these two values at a later date, across a number of mineral
samples, if the materials are uncontaminated and truly cogenetic, we will
find that they plot on a line. If we make 1 the X-axis and 2 the Y-axis
of a graph, the X-intercept of this line will give the original value of
1. It's slope is proportional to the number of half-lives since the
minerals formed.
> observes another person (#2) reading a book. The book opens to page 100
> at the time of entrance of #1. One minute later, #2 turns the page to
> 101; another minute later, #2 turns the page to 102. #1 then conclude
> that prior to #1 entering the room, #2 has been in the room for 99-100
> minutes. Since (1) the person might not start at page 1, (2) the book
See above. We know what page the rock started on. We also know that the
forces required to change the decay rate would melt the rock and thus
remove any isochron.
> might have pages with fewer/more content and thus require fewer/more
> time to read, and (3) person #2 could be distracted by #1 somehow
> during the observation, or there are some circumstances to help/hinder
> #2 during the reading time previously, the method cannot provide a
> reasonable analysis of #2's time in the room reading."
>
> I am trying to find a suitable counter-arguement for this.
Learn the details of the isochron method.
> Specifically, are there any way of determining the following to ensure
> the decay-type of dating method?
> 1, the original composition of elements as starting condition;
Yes, the isochron method makes that determination as a part of the
method.
> 2, the rate does not change over time;
Rates have been changed experimentally. The process requires heating the
materials to a plasma. Clearly this has not happened since a currently-
available rock has formed.
> 3, the fact of observation and measurement, and the relevant conditions
> during an object's life time, would not influence the results.
Some things can contaminate. Geologists pick their samples with this in
mind. So do creationist geologists, by the way, seeking samples that are
undatable and then dating them in order to perpetuate the lie that
radiometric dates don't work.
And yes, that is about as ethical as stealing your opponent's king in
chess and then declaring victory. And it should be given just as much
credence.
--
Dave Oldridge+
ICQ 1800667
Puppet_Sock
[snip]
> ISTM that radon being in the decay chain for Uranium is
> inconvenient for a fast decay hypothesis. Its a mobile
> gas with a half-life of 3.825 days. If the production
> of it is increased by several orders of magnitude for
> a short while, wouldn't it would leave a disproportionate
> amount of decay product in fissures and other escape
> routes for the gas during that time frame?
This is a good idea, but you need to work it out in detail
before it makes sense.
222Rn has a half life of 3.825 days. After a month or
so, there will be very little left. After a year you'd be
very hard pressed to detect any at all. Other isotopes
of Rn have shorter half lives. What that means is, if
you look some years after some kind of event, you
will be left with decay products. And which decay
products depends on the kind of event, what isotopes
it produced, and how they were retained.
The Oklo natural reactor has been mentioned in this
thread. Roughly 2 billion years ago it went critical
on its own, with natural ground water as a moderator.
We know it was a reactor because we find isotopes
in it that match exactly, all up and down the periodic
table, what we would calculate from a nuclear reactor.
Including 2 billion years of subsequent decay. Indeed,
we can see details so clearly that we can estimate
that it had a power cycle of roughly 1/2 hour on, then
2 or 3 hours off, and that it did this many millions of
times before exhausting its fuel.
The thing about Oklo is that it is not a single data point.
Nor even two or three. It is literally hundreds of different
isotopes, all right in line with what we would expect a
reactor to look like 2 billion years after it operated.
Not just a smoking gun, but an entire smoking arsenal.
Physics two billion years ago was highly similar to what
physics is today.
And the other thing about Oklo is, we know it's a reactor
because the fission products, or their decay products,
are right where they were generated. After several million
cycles of boiling the ground water out of the rock then
having it flow back in. Then two billion years of ground
water flowing through porous sandstone. The stuff in the
Oklo reactor is (except for a very few chemicals) exactly
where it was produced. This is a rather marvelous source
of validation data for geological disposal of nuclear waste.
Socks
Andrew Arensburger
> A rather popular arguement that keeps on repeating itself on various
> boards is that such methods require a constant rate of decay with
> knowledge of starting condition and no outside influence, etc.
Hm. This made me think of something that might possibly be a
new creationist argument (since I haven't heard anyone try to make
it):
Radiometric dating relies on radioactive decay in rocks
proceeding at a known rate.
Radioactivity is fundamentally a quantum phenomenon.
One important lesson from quantum physics is that particles
can behave as particles or as waves; it all depends on how one is
measuring them. Or, more generally, the experimental setup affects the
types of results measured, perhaps even more than in classical
mechanics.
Therefore, radioactive decay didn't occur until people started
measuring it with Geiger counters. Therefore, radiometric dating
methods are completely wrong.
QED. SPQR. PDQ.
Ignore the fact that this would make the universe look older
than it is, which is of no help to the YECs.
--
Andrew Arensburger, Systems guy University of Maryland
arensb.no-...@umd.edu Office of Information Technology
If it weren't for muscle spasms, I wouldn't get any exercise at all.
Robert Carnegie
> So the rate of decay of carbon-14 in the past has not changed, [and that is]
> as expected. Calculations of age based on that rate have been confirmed
> via independent means.
However, the abundance of carbon-14 has varied over time. That isn't a
problem, though. Or, rather, it's a problem that has been dealt with.
The basic principle, that material starts out with a mixture of carbon
12, 13, and 14, and the carbon-14 decays over time, stands up. But the
book-reading analogy does apply, a bit; in different centuries you get
a different mixture going in.
> However, the confirmation of C-14 accuracy already brings you back
> some 50,000 years, which is far older than the 6,000 year age of the
> YEC's imaginary world.
Yeah. The fact that radiocarbon dating has a limit on its useful range
actually knocks out the 6,009 year creationists, and the 8,000 year and
10,000 and 20,000 year ones. (Slippery bastards.) But the idea was
already busted before radioactivity, before Darwin, by layers in rocks,
pointing to steady processing continuing for millions of years. We did
have to work harder for billions. For one thing, to see how the sun
kept on burning for as long as /that/.
carlip...@physics.ucdavis.edu
[...]
> A rather popular arguement that keeps on repeating itself on various
Let me just address this part (cribbing liberally from previous posts
of mine on the topic...).
First, the physics of radioactive decay is quite well understood.
For the case of alpha decay, the simple underlying mechanism is
quantum mechanical tunneling through a potential barrier. You will
find a simple explanation in any elementary quantum mechanics
textbook; for example, Ohanian's _Principles of Quantum Mechanics_
has a nice example of alpha decay on page 89. The fact that the
process is probabilistic, and the exponential dependence on time,
are straightforward consequences of quantum mechanics. (The time
dependence is a case of "Fermi's golden rule" -- see, for example,
page 292 of Ohanian.)
An exact computation of decay rates is, of course, quite a bit more
complicated, since it requires a detailed understanding of the shape
of the potential barrier. In principle, this is computable from
quantum chromodynamics, but in practice the computation is much too
complex to be done in the near future. There are, however, reliable
approximations available, and in addition the shape of the potential
can be measured experimentally.
For beta decay, the underlying fundamental theory is different;
one begins with electroweak theory (for which Glashow, Weinberg and
Salam won their Nobel prize) rather than quantum chromodynamics.
For gamma decay, one again needs electroweak theory. In each case,
though, the underlying physics is well understood.
As described above, the process of radioactive decay is predicated on
rather fundamental properties of matter. In particular, in order to
explain old isotopic ages on a young Earth by means of accelerated
decay, an increase of six to ten orders of magnitude in rates of decay
would be needed.
Now, the fundamental laws of physics, as we presently understand them,
depend on about 25 parameters, such as Planck's constant h, Newton's
gravitational constant G, and the mass and charge of the electron,
and a change in radioactive decay rates would require a change in
one or more of these constants. The idea that these constants might
change over time is not new, and is certainly not restricted to
creationists. Interest in this question was spurred by Dirac's
"large number hypothesis." The "large number" in question is the
ratio of the electric and the gravitational force between two electrons,
which is about 10^40; there is no obvious explanation of why such a
huge number should appear in physics. Dirac pointed out that this
number is nearly the same as the age of the Universe in atomic units,
and suggested in 1937 that this coincidence could be understood if
fundamental constants -- in particular, Newton's gravitational constant
G -- varied as the Universe aged. The ratio of electromagnetic and
gravitational interactions would then be large simply because the
Universe is old. Such a variation lies outside ordinary general
relativity, but can be incorporated by a fairly simple modification
of the theory. Other models, including the Brans-Dicke theory of
gravity and some versions of superstring theory, also predict physical
"constants" that vary.
Frankly, physicists are not, for the most part, interested in silly
creationist arguments. But they are interested in basic questions
such as whether physical constants or laws change in time --
especially if such changes are proposed by such a great physicist
as Dirac. As a result, there has been a great deal of experimental
effort to search for such changes. A nice (technical) summary is
given by Sisterna and Vucetich, Physical Review D41 (1990) 1034 and
Physical Review D44 (1991) 3096; a more recent reference is Uzan,
Reviews of Modern Physics 75 (2003) 403, available electronically
at http://arxiv.org/abs/hep-ph/0205340. Among the phenomena they
look at are:
* searches for changes in the radius of Mercury, the Moon, and
Mars (these would change because of changes in the strength of
interactions within the materials that they are formed from);
* searches for long term ("secular") changes in the orbits of
the Moon and the Earth --- measured by looking at such diverse
phenomena as ancient solar eclipses and coral growth patterns;
* ranging data for the distance from Earth to Mars, using the
Viking spacecraft;
* data on the orbital motion of a binary pulsar PSR 1913+16;
* observations of long-lived isotopes that decay by beta decay
(Re 187, K 40, Rb 87) and comparisons to isotopes that decay by
different mechanisms;
* the Oklo natural nuclear reactor (mentioned in another
posting);
* experimental searches for differences in gravitational
attraction between different elements (Eotvos-type experiments);
* absorption lines of quasars (fine structure and hyperfine
splittings);
* laboratory searches for changes in the mass difference
between the K0 meson and its antiparticle;
* searches for geological evidence of "exotic" decays, such
as double beta decay of Uranium 238 or the decay of Osmium to
Rhenium by electron emission, which are impossible with the
present values of basic physical constants but would become
possible if these changed;
* laboratory comparisons of atomic clocks that rely on
different atomic processes (e.g., fine structure vs. hyperfine
transitions);
* analysis of the effect of varying "constants" on primordial
nucleosynthesis in the very early Universe.
While it is not obvious, each of these observations is sensitive
to changes in the physical constants that control radioactive decay.
For example, a change in the strength of weak interactions (which
govern beta decay) would have different effects on the binding energy,
and therefore the gravitational attraction, of different elements.
Similarly, such changes in binding energy would affect orbital motion,
while (more directly) changes in interaction strengths would affect
the spectra we observe in distant stars.
The observations are a mixture of very sensitive laboratory tests,
which do not go very far back in time but are able to detect extremely
small changes, and astronomical observations, which are somewhat less
precise but which look back in time. (Remember that processes we
observe in a star a million light years away are telling us about
physics a million years ago.) While any single observation is subject
to debate about methodology, the combined results of such a large
number of independent tests are hard to argue with.
The overall result is that no one has found any evidence of changes
in fundamental constants, to an accuracy of about a part in 10^11
per year. There are some recent, controversial claims of observational
evidence for changes in certain constants (notably the "fine structure
constant") in the early Universe, but these are *tiny*, and would have
minimal effects on radioactive decay rates.
So the idea that decay rates could vary enough to make a significant
difference to measurements of ages is ruled out experimentally.
Steve Carlip
Jon Fleming
<dold...@leavethisoutshaw.ca> wrote:
>"AllanL" <darkne...@hotmail.com> wrote in news:1156114257.419311.66540
>@75g2000cwc.googlegroups.com:
<snip>
>> 2, the rate does not change over time;
>
>Rates have been changed experimentally. The process requires heating the
>materials to a plasma. Clearly this has not happened since a currently-
>available rock has formed.
See also http://physicsweb.org/articles/news/10/7/13/1
<snip>
Jon Fleming
--
B Richardson
Stanley Friesen
Note that the Uncertainty principle *does* apply to virtually all of
quantum physics, but not in the way it is popularly imagined. Indeed
the very *existence* of radioactivity is due to the Uncertainty
Principle (it is related to the fact that energy and time are
non-commuting variables, much as position and momentum are).
--
The peace of God be with you.
Stanley Friesen