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Fraser
2005-Sep-11, 05:24 AM
SUMMARY: On August 14, a new detector designed to determine the mass of neutrinos began operations in an old mine in Minnesota, USA. The Main Injector Neutrino Oscillation Search (MINOS) detector is 30-metres long and consists of 486 massive octagonal plates, each of which is 8-metres across. MINOS will initially measure neutrinos coming from Sun, but in August 2004 it will measure man-made neutrinos created in a laboratory more than 700 km away. If the experiment is successful it will help solve the mystery of dark matter, which some astronomers believe comes from the mass of neutrinos.

View full article (http://www.universetoday.com/am/publish/neutrino_mass_detector.html)
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trinitree88
2005-Sep-29, 11:44 PM
Neutrinos are generally considered to be the most penetrating particles in the universe. Just as you would not expect a piece of tissue paper to shield you from the gamma rays emitted by a nuclear reactor ( they use steel and concrete for that), you wouldn't expect an ordinary dime store mirror to protect you from a supernova's prompt neutrino burst. But, if they are massive, it can.
Massive neutrinos cannot travel at the velocity of light. That's prohibited by the Special Theory of Relativity. It would take all of the energy of the entire universe, plus the conversion of all of the other masses in the universe to energy according to E=mc squared, applied together to the massive neutrino and still, it could not achieve c , according to The Special Theory......one never seen inviolate yet.
But, since the prompt burst massive neutrinos are traveling subluminal, we could at least in principle travel in our space ship closer to the speed of light than they do......very expensive spaceship, but at least theoretically valid. Now, we place a Cherenkov cone water detector at the rear of our spaceship...similar to the IMB. If a star goes supernova behind us, the prompt burst sets off the photomultiplier tubes. The signal is radioed to the front of the ship, outracing the burst. Front mounted electromagnetic rail guns fire projectiles rearward, bringing the ship even closer to the speed of light, just as the burst reaches the hand held mirror.....and LO!.....the burst reflects from the mirrored surface, as it outstrips the slower,massive neutrinos, which recede slowly back through the ship.
We now have in the same reference frame the paradoxical result that neutrinos are the most penetrating particles in the universe, and yet at the same time are easily completely reflected by a dime store mirror, just as the image of your face is. Which is it? :think: Ciao. Pete

Duane
2005-Sep-30, 01:10 AM
This is a very old story (Aug 2003).

trinitree88
2005-Oct-01, 11:13 AM
Hi. Pete, here. I would like to make one additional point about massive neutrinos. One can envision a neutrino and it's counterpart antineutrino as a pair of helices of opposite handedness. One right-handed, the other, lefethanded, spiraling their way through space. In an analagous sense....right and left handed screws from the hardware store. The right-handed screw travels away from you and into the wood, as you turn it clockwise.....the left-handed screw, backs off from the wood, and comes towards you as it turns clockwise. So if a neutrino maintains it's helicity, and reflects backwards (backscatter) off a dime store mirror....it converts to an antineutrino of the same family.....a violation of Electron, or Muon, or Tau Family Number Conservation.....something never seen in a particle physics experiment anywhere. All their detector codes are primed in Conservation Laws.
So, positing a non-zero neutrino mass, means throwing away a conservation law. Not my idea....a very sharp young Japanese physicist thought this through. He's right. :think: Ciao. Pete.