The half life for Sm – 146 has
been cut from 103 my down to 68 my. That
is pretty significant and the immediate
impact has been to clean up some vexing discrepancies out there.
The underlying assumption
continues to be that the half life is invariant. It may be, but it is the first thing that I would
expect to see altered if we passed through a zone of ‘dark matter’. Such a zone would surely increase the rate of
nuclear decay as some of the dark matter is absorbed into the atoms. (I will not explain this at the moment) I suspect that our exposure to dark matter
varies greatly as we travel around the Galaxy and radiactive decay rates vary
accordingly.
Actually there is an experiment
that I would like to see conducted. I
would like to determine if the decay rate of a range of radioactive materials varies
in terms of our position in the solar orbit and our position in terms of the
sun and the bow wave. We might just get
lucky.
New Isotope Measurement Could Alter History of Early Solar System
ScienceDaily (Apr. 3, 2012) — The early days of our solar system
might look quite different than previously thought, according to research at
the U.S. Department of Energy's (DOE) Argonne National Laboratory published in Science.
The study used more sensitive instruments to find a different half-life for
samarium, one of the isotopes used to chart the evolution of the solar system.
"It shrinks the chronology of early events in the solar system,
like the formation of planets, into a shorter time span," said Argonne physicist Michael Paul. "It also means some
of the oldest rocks on Earth would have formed even earlier -- as early as 120
million years after the solar system formed, in one case of Greenland
rocks."
According to current theory, everything in our solar system formed from
star dust several billion years ago. Some of this dust was formed in giant
supernovae explosions which supplied most of our heavy elements. One of these
is the isotope samarium-146.
Samarium-146, or Sm-146, is unstable and occasionally emits a particle,
which changes the atom into a different element. Using the same technique as
radiocarbon dating, scientists can calculate how long it's been since the
Sm-146 was created. Because Sm-146 decays extremely slowly -- on the
order of millions of years -- many models use it to help determine the age of
the solar system.
The number of years it takes for an isotope to decrease by half is
called its half-life. Since Sm-146 emits particles so rarely, it takes a
sophisticated instrument to measure this half-life.
The Argonne Tandem Linac Accelerator
System, or ATLAS, is a DOE national user facility for the study of nuclear
structure and astrophysics, and is just such an instrument. "It's easy for
the ATLAS, used as a mass spectrometer, to pick out one Sm-146 atom in tens of
billions of atoms," said physicist Richard Pardo, who manages the facility
and participated in the study.
By counting Sm-146 atoms with ATLAS and tracking the particles that the
sample emits, the team came up with a new calculation for its half-life: just
68 million years.
This is significantly shorter than the previously used value of 103
million years.
The new value patches some holes in current understanding, according
to Paul. "The new time scale now matches up with a recent, precise dating
taken from a lunar rock, and is in better agreement with dates obtained with
other chronometers," Paul said.
The study was recently published in Science. Argonne
scientists Catherine Deibel, Brad DiGiovine, John Greene, Dale Henderson,
Cheng-Lie Jiang, Scott Marley, K. Ernst Rehm, Robert Scott, and Richard
Vondrasek also participated in the study.
The work was supported by the DOE Office of Science and the Japan
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