<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[Ben]: any thoughts on the probability that one or more type’s of neutrinos are responsible for gravity?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
Neutrinos are detected in insignificant quantities in the universe compared with the kinds of fluxes needed for gravitons. Neutrino speeds are limited by the speed of light, gravitons are not. Neutrino masses (if they are particles and not waves) are many orders of magnitude larger than even elysons, which are in turn many orders of magnitude bigger than gravitons.
This suggestion about neutrinos comes up from time to time. It is a good thought. But the properties are not right. Neutrinos do illustrate the point, however, that it is easy for small entities to fly through the entire Earth without noticing.
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[Rudolf]: The one thing I have not seen is proof that neutrinos actually move at lightspeed - this has probably been assumed because of SR.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
If neutrinos are waves, they must move at lightspeed. If they are particles, they must move at less than lightspeed, but only by a tiny bit. We know that neutrinos arrive from distant supernovas about the same time as the light arrives, so their speed cannot be far from lightspeed.
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[Magoo]: If ... neutrinos have mass then they can't travel at lightspeed, Right?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
One experiment suggests that neutrinos have mass, but that conclusion is not yet widely accepted as definite. But the implications for speed are not very much, either way.
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[rush]: I have no clue about neutrinos, so: How do we know that neutrinos does in fact exist?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
They are detected in experiments (huge underground detectors). For the last generation, the number of neutrinos observed to be coming from the Sun has been 1/3 to 1/2 less than the number predicted by theory. That discrepancy is currently resolved by assuming that neutrinos change type while in transit, thereby avoiding detection. That can only happen if they have mass. Hence, the belief that they do. But another possible explanation is gravitational shielding in the Sun's interior. So we may still have much to learn about neutrinos in astrophysics. -|Tom|-
