From: Karl Lembke 9 Jul 94 11:23
To : Bob Sewell
Subj: Constant Decay
-=> Quoting Bob Sewell to C. J. Henshaw <=-
BS> On (30 Jun 94) C. J. Henshaw wrote to Bob Sewell...
MG>> the decay of radioactive isotopes of the elements is constant.
MG>> This by itself makes it reliable.
BS> You've taken samples over the last few thousand years to verify this?
While no one has sat around for a thousand years (or a million
or a billion) to watch a long-lived nuclide decay, certain properties
have been observed for -=ALL=- radioactive nuclides, which lead
scientists to conclude that they will behave according to the same
laws. Thus, iodine 131 (half life = 8 days), carbon 11 (half life
= 20.3 minutes), Sodium-22 (half life 2.6 years), oxygen 14 (half life
71 seconds), and all the other short lived nuclides behave enough
like the long lived ones that it seems only reasonable to conclude
that they will continue to behave the same way.
All radionuclides which have been observed for long enough have been
found to decay according to an exponential curve. Thus, the rate of
decay is always proportional to the amount of the nuclide present.
If we have a gram of potassium-40 in a lab, and we count the number
of potassium-40 atomss that decay in a second, we will find that
something like 372,554 atoms will do so. This number won't be exact,
but after several measurements, we will find that this is the average
number, with a standard deviation of 610 counts.
This number, the 372,554 represents a constant fraction of the number
of atoms present. Double the amount of K-40, double the observed
count. Halve the amount present (or let half of it decay away),
and we halve the observed count. Thus, the rate at which atoms
decay, thus disappearing from the sample, by becoming something
else, is proportional to the amount of the nuclide in question.
Mathematically, we say that the rate of decay is equal to a constant
times the quantity of the substance being examined.
Y' = -kY
(The minus sign is present because the rate is a decay rate, or a
negative change in quantity.)
This is a differential equation, since Y' is the derivative of Y.
The solution of this equation is
Y =Y0 * exp(-kt)
Thus, when a gram of radium yields a count of 3.7E10 disintegrations
per second, solving the differential equations for the rate of
observed decay, we find (and have no reason to doubt) that radium-226
has a half life of 1600 years.
CJ> to challenge the laws of physics?
BS> Nope. Just questioning the assumption that decay rates have always
BS> been constant and have never been affected by external events, (e.g.,
BS> increases in neutrino flux due to past intermittent increases in
BS> cosmic radiation at the earth's surface, caused by, say, supernova
BS> explosions in nearby stars) that might change those decay rates. Dr.
BS> Frederick Jueneman, director of research for the Innovative Concepts
BS> Association, wrote in September 1972's "Scientific Speculation:"
The thing is, nuclear decay has been observed to be constant, that is,
the rate refuses to vary, despite any number of things people have
thrown at radioactive samples. The rate remains constant over wide
ranges of pressure, temperature, electric and magnetic field
strengths, and so on. Anyone who claims that the rate of decay
can be made to vary had better be able to show a mechanism.
BS> "Being so close, the anisotropic neutrino flux of the
BS> super-explosion must have had the peculiar characteristic
BS> of resetting all our atomic clocks. This would knock our
BS> Carbon-14, Potassium-Argon, and Uranium-Lead dating
BS> measurements into a cocked hat! The age of prehistoric
BS> artifacts, the age of the earth, and that of the universe
BS> would be thrown into doubt."
Particle bombardment will change the rate at which the sample disappears,
by initiating nuclear reactions peculiar to the type of bombardment
Nutrino bombardment could initiate a slew of reactions, most notably
inverse beta decay and electron capture reactions, and this could
change the amount of a nuclide in any given sample. For example,
in a sample high in nitrogen 14 a high nutrino flux could
conceivably turn some of the N-14 into C-14, making the sample appear
artifically young. But this same flux would operate on other atoms
in the sample, creating weird nuclides in the process.
BS> Some fellow named John L. Anderson published, in "Abstracts of
BS> Papers for the 161st National Meeting, Los Angeles" (March 1971) the
BS> results of some experiments which have shown that C-14 decay rates
BS> actually could have varied in the past to an extent which would render
BS> invalid most ages measured with radiocarbon dating methods.
161st national meeting of what? Were the papers presented peer
reviewed or referreed? What is Mr. Anderson's background?
Is there any way someone could get a copy of that paper?
Someone who had managed to show a real hole in the assumption that
Y = Y0 * exp(-kt) for all radionuclides would be quite famous.
... Nothing so needs reforming as other people's habits.
___ Blue Wave/QWK v2.12