From: Gina Miller (echoz@hotmail.com)
Date: Thu Apr 29 1999 - 23:14:06 MDT
Measuring The Cosmic Neutrino Background
The cosmic neutrino background can, in principle, be detected, according to
the American Institute of Physics' Physics News Update for April 27. There
are, the Bulletin points out, almost as many neutrinos loose in the universe
as photons, and almost as much energy vested in neutrinos as in photons.
But because neutrinos are extremely reticent about interacting with other
particles, detecting the neutrino background is not as easy as detecting the
cosmic photon (microwave) background. That's why dedicated neutrino
detectors struggle just to record a handful of incoming neutrinos from
potent nearby sources such as the sun.
Nevertheless, the Bulletin says, there might be a chance to map the
background indirectly: The pattern of lumps in the microwave background,
which will be measured by the upcoming MAP and PLANCK orbiting detectors, in
fact encodes information about the neutrino background.
(The PLANCK mission is a European Space Agency project to image the
temperature anisotropies of the cosmic microwave background radiation. The
whole sky will be mapped in nine frequency channels ranging between 30 and
900 GHz, with a sensitivity and an angular resolution that will allow the
separation of the cosmological signal from all other sources of confusion.)
Scott Dodelson of Fermilab, Michael Turner and Robert Lopez of the
University of Chicago and Andrew Heckler of Ohio State, in an upcoming
article in Physical Review Letters, show that these measurements will
accurately establish the time at which slow-moving matter (protons and later
atoms) became predominant over fast-moving radiation (photons and
neutrinos). In turn, they write, this determines precisely how much early
annihilation energy (arising from electrons and positrons smashing up) was
apportioned among photons and neutrinos.
[Contact: Phillip F. Schewe, Ben Stein]
29-Apr-1999
© 1995-1999 UniSci. All rights reserved.
Gina "Nanogirl" Miller
Nanotechnology Industries
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