Weird Antimatter Particles Discovered Deep Underground
Clara Moskowitz
LiveScience Senior Writer
www.LiveScience.com
http://www.livescience.com/strangenews/antimatter-particles-geoneutrinos-underground-100625.html
"Exotic antimatter particles have been detected deep within the Earth's
interior, scientists report.
"Studying these particles, which are thought to result from radioactive
decay within Earth, could help scientists better understand how the flow
of heat inside our planet affects surface events like volcanoes and
earthquakes."
"The particles, called geoneutrinos, are made of a strange type of
matter called antimatter, which has properties opposite those of regular
matter. When a regular particle, like an electron, meets with its
antimatter partner, called a positron, the two annihilate each other in
an energetic explosion."
"Geoneutrinos are the antimatter partners of neutrinos, which are very
lightweight, neutrally charged particles that are created within the
sun, and when a cosmic ray strikes a normal atom. An earlier project
called KamLAND in Japan found the first signs of possible geoneutrinos
in 2005."
A giant steel sphere
"Researchers in the Borexino collaboration at the Gran Sasso National
Laboratory of the Italian Institute of Nuclear Physics discovered the
geoneutrinos inside a nylon sphere detector containing 1,000 tons of a
hydrocarbon liquid. This sphere is encased within a larger stainless
steel sphere in which an array of ultra-sensitive photodetectors point
at the inner nylon globe. Both of these layers are enclosed within a
third 45 foot (13.7 meter) diameter steel sphere holding 2,400 tons of
highly purified water.
"The whole experiment is buried nearly a mile below the surface of the
Gran Sasso mountain in Italy. [Image of giant steel sphere]
"All of these "fortifications" serve to shield the experiment from
detecting anything other than neutrinos and geoneutrinos. These
particles are incredibly difficult to find, because they pass through
almost everything without interacting in any way.
Over a whole year of searching for the elusive geoneutrinos, the
experiment detected only a few signals. The detection of solar
neutrinos, which produces a different pattern, is somewhat more common.
"The researchers detailed their results from two years of operations -
running through December 2009 - in a paper published in the April issue
of the journal Physics Letters B.
"This is an important result," co-researcher Frank Calaprice, a
physicist at Princeton University in New Jersey, said in a statement.
"It shows that geoneutrinos have been detected and firmly establishes a
new tool to study the interior of the Earth."
The Earth's inner warmth
"Geoneutrinos are thought to be formed from the radioactive decay of
uranium, thorium, and potassium inside the Earth's crust (its outermost
layer) and mantle (the layer below that, extending to 1,800 miles, or
2,900 km, beneath the surface).
"The researchers hope that by studying geoneutrinos, they can learn more
about how decaying elements add to the heat beneath Earth's surface and
affect processes like convection in the mantle. Whether radioactive
decay dominates the heating in this layer, or merely adds to the heat
from other sources, is an open question.
"Convection is a process of heat-driven mixing that pushes a flow of hot
rock from deep in the interior up to the planet's surface. This drives
plate tectonics, shifting the continents, spreading the seafloor, and
causing volcanoes to erupt and earthquakes to tremble.
"The results of the new study suggest the radioactivity within Earth
probably contributes a significant fraction of the heat in the mantle,
Calaprice said."
[A correspondent comments:
"This has been a well-known fact for a long, long time. In fact,
before the discovery of radioactivity, the big mystery of geophysics
was where does the heat come from that keeps the core of the Earth
molten and keeps the mantle hot - thus causing volcanic eruptions and
other phenomena. This was a big problem that was brought up by
Rayleigh and/or Lord Kelvin.
"Then, after radioactivity was discovered by Becquerel, the Curies,
etc., it became clear that the extra heat within the Earth was created
by radioactive decay. Otherwise, the interior of the Earth
would have solidified billions of years ago; they Earth would not have
a significant magnetic field - hence no Van Allen belts; and there would
be no volcanoes, no geysers, no plate tectonics, no earthquakes, etc." ]
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