Neutrino mass

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pete-6
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Neutrino mass

Post by pete-6 »

Physics in the news. Anyone else pick up this story this morning ('Today' programme)? I don't know which kind of neutrino they were referring to. They were a bit obscure and trivialising in the way they presented the figure ("100 billion billion billion billionth of mass of a human body" - if I've done my sums right I think they mean 1E-36Kg or about 0.5eV) this would be a sensational bit of news if they mean a lower bound - or median value. Plenty of upper bounds have been published for years now - I think the best one at present for the electron-neutrino is about 2.5eV. But a lower bound would have tremendous implications in - well - just about every branch of cosmology and astrophysics. What does it tell us about dark matter?
Pete
joe
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Post by joe »

No, I didn't hear that. Thanks.
200mm Newtonian, OMC140, ETX90, 15x70 Binoculars.
Cliff
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Post by Cliff »

Dear Pete-6
Like Joe I did not see the broadcasted gen you mentioned.
To be honest I doubt the figures you quoted would have meant very much to me.
The only thing I might mention is that although I gather there are different types of neutrino at least some neutrinos have mass (which I think is very small but I am not sure every type of neutrino necessarily has exactly the same mass. I also think I read that neutrinos can possibly change from one type to another. If that is the case can neutrinos change mass.
Best wishes from Cliff
KendalAstronomer
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Post by KendalAstronomer »

Yes Cliff, you are correct. There are three 'flavours' of neutrino - electron, tau and muon, named after the particles created with them. There are free anti-neutrinoes as well. The theory that they change from one type to another is called 'neutrino oscillation'. This idea was dreamt up to explain the solar neutrino problem where the numbers of neutrinoes measured from the Sun didn't match the number expected by a long way. Neutrinos are extremely hard to detect anyway, but each of the three flavours has its own detectability, meaning scientists can only really measure one of them, and sort of measure another. The idea was the naughty neutrinos were being created in the Sun and then some of them changed from the easier to detect ones to the harder to detect ones and that's why the easier to detect ones don't appear in the right numbers.

Central to neutrino oscillations (apparently similar to the 'beats' effect, when you have two similar notes playing, they seem to oscillate and produce a third) was the idea that neutrinos required different masses to give them different frequencies. Eventually, a mass difference was confirmed.

So the flavours have different masses and switch from one to another (or at least appear to)... story continues...
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Post by Cliff »

Dear KendalAstronomer
Many thanks for your comments!
To say I am more confused than ever would be an understatement, but nothing new. However, the continuing story will be of great interest.
Best wishes from Cliff
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