Low-Energy Neutrinos Detected In Real Time

Roland Piquepaille sends us word of first results from the Borexino detector in Italy, where an international team of more than 100 researchers has detected low-energy solar neutrinos for the first time. These results confirm recent "theories about the nature of neutrinos and the inner workings of the sun and other stars." In particular, it's now almost certain that neutrinos oscillate among three types, namely electron, muon, and tau neutrinos. The Borexino detector lies almost a mile underground near L'Aquila, Italy, and it sets new standards in the purity of the materials used in its construction.

Neutrinos massless = timeless, but change state?

[elmartinos]

Last time I have heard something about the Neutrinos, there was an unresolved problem: Neutrinos do not have mass, therefore travel at the speed of light. But since they travel at the speed of light they have no sense of time, and therefore it should not be possible for them to change their state as they are practically frozen in time. This and earlier experiments confirm that despite that they change state. Are there already theories why this is possible?

Re:Neutrinos massless = timeless, but change state

[Anonymous Coward]

Why are we so sure that photons are massless? Is it something just assumed, or has it been measured? Has it been measured accurately enough?

Obviously, photons move at the speed of light (by definition). But if they too have 'immeasurably small', not 'zero' mass, that has some rather interesting implications for physics, does it not?

[Disclaimer: IAAP, although I don't work in this area.]

Just to clarify, when you talk about photons having mass, you mean nonzero rest mass. Photons already behave in many ways as though they have mass because they have energy.

I think the short answer is: if photons had mass, even small mass, then EM radiation would be dispersive in a vacuum, i.e., different wavelengths would travel at different speeds. I don't think this has been observed. A recent article [slashdot.org] did report something along those lines, but I didn't see any mention of nonzero-rest-mass photons as an explanation. Rather, they're interpreting the results as a possible verification of one of the predictions of string theory: that high-energy photons induce spacetime lensing that slows them down ever-so-slightly compared to their low-energy counterparts. Hey, who knows -- maybe someone could come up with a nonzero-mass photon theory to explain the results. Or maybe the string theorists are doing that already. I don't know -- like I said, I don't work in this area.

Has anyone looked for similar alternative states in photons?

See above.