u think that the univers is realy expanding?? think again

darkness_limits

well i readed recently in a physics magazine that the scientist are trying to find if the neutrino has any mass , if it is true then the univers will be contracting and not expanding and the big bang theorie is false.. what is the relation ?

ZapperZ

Er... you are about 10 years too late. We ALREADY know the neutrinos have mass! The neutrino oscillation experiments have been going on for the past 10 years, at least. This has no effect on the universe expansion as of yet. In fact, the whole reason for the "dark energy" scenario is due to the more recent observation that the universe seems to be expanding at an even faster rate than expected!

Zz.

Chronos

Even worse, the neutrino 'mass' is far too insignificant to affect the 'big picture' of expansion. It is not a viable candidate to explain 'dark matter' or assert it's place as the 'missing mass' in a Lamda universe.

hellfire

This is correct. I would like to emphasize that the mass of the known neutrinos is too insignificant. However, the existence of a heavy fourth generation neutrino has been recently postulated in order to correct the too cuspy density profiles of a pure cold dark matter model. See for example: Constraining Warm Dark Matter candidates including sterile neutrinos and light gravitinos with WMAP and the Lyman-alpha forest.

ZapperZ

Er.. are you sure? I thought the recent MiniBooNE experimental results kinda dashed that hope?

Zz.

hellfire

You might be right. I was relying on the wikipedia article about MiniBooNe that claims that there are indications pointing towards the existence of the sterile neutrino and that this information is more recent than the april paper also mentioned there (and that I assume to be the source for the physicsworld article you have linked). However, I've checked now the MiniBooNe web and I was not able to find any more recent information. It seams that the wikipedia article is not very accurate.

ZapperZ

That goes without saying.

Trust Wikipedia at your own risk.

Zz.

Chronos

The quality of articles on Wiki vary wildely, and daily. It is an unreliable source, IMO.

Parlyne

Not really. The LSND signal that MiniBooNE was trying to reproduce is in the wrong region of the sterile neutrino parameter space to account for warm dark matter.

ZapperZ

But even LSND has backed down from its own findings when it couldn't find it again, no? Or am I thinking of another experiment here?

Zz.

Parlyne

My point was that MiniBooNE does not rule out the full parameter space for sterile neutrinos. The big news back in April was that it had found nothing where the hint of a signal reported by LSND had been. This is in a region of the parameter space quite remote from any sort of dark matter candidate.