THE SOUTHWORTH PLANETARIUM
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Founded January 1970
               "Heavens below!"


THE DAILY ASTRONOMER
Tuesday, March 22, 2016
Nuclear Bombs and Art Forgery


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*** Live at 1:00 p.,m.  22 - Everyone is welcome! ***
Join us on Tuesday March 22nd at 1 p.m. EST for a LIVE event with
Astrobiologist and Planetary Scientist Dr. Nathalie Cabrol:

Talk to an Astrobiologist: Nathalie Cabrol
<http://saganet.org/events/event/show?id=6441647:Event:57751&xgs=1&xg_source=msg_share_event>
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If astronomy teaches us anything, it's that we're all muddling through
a complex, entangled world of intricate interconnections.    One can't
toss a test charge onto the grid corner without contorting the entire
works with those pesky field lines.   Or, to cite a more popular
example, we know that a butterfly flapping its wings in Antarctica will
cause a lepidopterist to raise an eyebrow in Colorado.  And, if little
charges and butterflies can wreak such cumulative havoc, one can't even
imagine what detonated nuclear weapons can do to this dynamic little
planet.

That is part of the fun, of course:  that we often cannot foresee the
ramifications of our actions in this beautifully non-linear Universe.
(Nature is a better chess player.)    So, when mid 20th century nuclear
physicists tested their atomic weapons -and the military deployed their
two- life changed irrevocably on Earth.  We'll happily eschew the
political and philosophical aspects and focus on the radiative.

Nuclear weapons introduce vast radiation throughout their local impact
area and, eventually, through the world.     While the amounts in more
distant regions don't pose a health threat -we think- they can affect
life forms in myriad ways.   Consequently, they also complicate
scientific processes employed to study these life forms    Perhaps the
most profound change relates to Carbon-dating: the age determination
technique that is often employed archaeologically, but explainable
astronomically.

We offer a neat textbook example:

Plants absorb carbon dioxide, a nifty little molecule comprised of one
carbon molecule connected to two oxygen molecules.   While all carbon
dioxide molecules exhibit consistent chemical properties -i.e. we can't
inhale any of them- not all carbon dioxide molecules are created equal.
Most of them use the stable carbon-12 atom, twelve referring to the six
protons and six neutrons in the nucleus. A few, however, use the
unstable carbon-14 atom, with six protons and eight neutrons.  (Note:
the proton number determines the element.  Add a proton to make seven
and suddenly you have a nitrogen atom.)

Carbon-12 comprises more than ninety-nine percent of all carbon on
Earth.    The other two isotopes, Carbon-13 and Carbon 14, represent the
remaining one-percent, with C-13 making up most of that one-percent.
While one would find only one lonely C-14 atom for every trillion C-12,
the ratio remains more or less constant because the process required to
make Carbon-14 hasn't changed.  (Hint: we'll get back to that "more or
less" part soon.)

Carbon-14 production occurs in the upper troposphere and lower
stratosphere.*  When high energy cosmic rays enters the atmosphere, some
will collide with atoms, producing what we call "thermal neutrons."  All
we need to know about these little monsters is that they are readily
absorbed, primarily by Nitrogen atoms.   The nitrogen absorbs the
neutron and in the process emits a proton, becoming a carbon-14 atom.

A carbon-14 atom is born, but, unlike carbon-12, it is unstable and
will revert back into a nitrogen.**   Although we cannot know when a
precise atom will decay, we can know when a certain propotion of
carbon-14 will transmute into nitrogen-14.    The actual term is
"half-life," which measures the time required for half of a given sample
to decay.   Carbon-14's half life is 5,730 years.    So, for instance,
if we collected 10 grams of C-14 in a jar, in 5,730 years, 5 grams will
have become nitrogen-14.    We'd have to wait another 5,730 years for
another 2.5 grams to become nitrogen.

A plant absorbs both C-12 and C-14 throughout its life, but stops
absorbing them when it dies.    The amount of C-12 remains constant, but
the C-14 slowly decays.     When we analyze a sample of plant tissue, we
can determine when it died by measuring the C-14 to C-12 ratio.    If we
were impatient and measured the tissue five minute after the plant
grabbed its chest and collapsed to the ground, we'd find its C-14/C-12
ratio to be about 1 to one trillion.  That is what we'd expect, after
all, as our subject hasn't had any time to allow its C-14 stores to
decay.   If, however, we waited 5,730 years after death, the ratio would
be one half that of the first measurement:  half of the C-14 is gone.
  Provided we have the math, we can ascertain the plant's approximate
death year (or range of years) simply by knowing the C-14/C-12 ratio.

 The problem with this process is that it's affected by variable
factors, such as Earth's magnetic field, which shields the planet from
many cosmic rays.  The stronger this fluctuating magnetic field becomes,
the greater the repulsion, which reduces the C-14 production rate.
And, also, those troublesome nuclear blasts produced a raging neutron
swarm that, obviously, affected C-14 production from below, as opposed
to the cosmic rays producing them from above.     Oppenheimer's trinkets
have rendered the radiocarbon dating method a little less reliable.

 But, then again, they have given a secret and surprising weapon to
those who seek out art forgeries.   To explain how, we imagine a
scenario in which a desperate planetarium astronomer strives to raise
funds by selling  Jan Vermeer's "The Astronomer" on E-bay with an
initial suggested bid of $12 million.    What he doesn't tell anyone is
that he brilliantly forged the oil on canvas in the planetarium dome the
week before.   Confident that nobody will know the difference -after
all, how many art historians would actually know the real painting was
currently on display at the Louvre?- he peddles it as the original 1688
painting on E-bay and waits for the torrents of cash to gush through the
doors.  Unfortunately, a chemist/art historian foils the plan by taking
a small paint sample.

 And, since the oil used, properly called linseed oil, derives from the
flax plant, said chemist determines that the painting couldn't possibly
be the original because the C-14/C-12 ratio is too high - indicating
that its constituent materials date from the post-nuclear era; as
opposed to the simple, pre-atomic bomb days of the late 17th century.

Too bad.    The astronomer's plans were woefully curtailed by one of
those pesky chemists…again.

Interconnectedness makes life so interesting, if not necessarily
profitable.    We are still just beginning to fathom all of nature's
machinations.  Moreover, the more we learn, the more we realize how much
we have left to learn.    Fortunately, science's infancy will keep the
astronomers employed, a good thing as some of them flop when attempting
other endeavors

*Troposphere: the lowest atmospheric region containing 80% of the
atmospheric gases by mass and extending up to about 16 kilometers at the
mid latitudes.  (It is thicker in the tropics and thinner at the
poles.)

Stratosphere: the layer above the troposphere.



**So,  here's the rub:   the neutron disintegrates back into a proton
and an electron.  It emits the electron as Beta radiation and retains
the extra proton, changing it back to a nitrogen atom.