Neutrinos have mass. AND they travel at c.
Neutrinos have mass. AND they travel at c.
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
They were thought to travel at c when they were thought to be massless. Now that they're thought to have mass, it's assumed they travel at a little less than c.
... definitely not FTLSo now I find out matter CAN go FTL!
How could anyone ever have thought that a particle of matter, a sibling to electrons, taus, and muons, could have been massless? Masslessness would have made it something else completely different from matter, something that didn't fit in with electrons and such!
Just so people know, robross ran into one of those quirks with allowed words in titles and did ask for it to be changed, but mods ran into the same issue.So now I find out matter CAN go FTL!
At night the stars put on a show for free (Carole King)
All moderation in purple - The rules
If we don't limit ourselves to the vacuum, FTL is possible.
See Cerenkov radiation. Make note it's not true FTL, since c does not decrease as it's defined as 'in vacuo'.
by John Updike
From Telephone Poles and Other Poems, Alfred A. Knopf, (1963).Neutrinos they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids down a drafty hall
Or photons through a sheet of glass.
They snub the most exquisite gas,
Ignore the most substantial wall,
Cold-shoulder steel and sounding brass,
Insult the stallion in his stall,
And, scorning barriers of class,
Infiltrate you and me! Like tall
And painless guillotines, they fall
Down through our heads into the grass.
At night, they enter at Nepal
And pierce the lover and his lass
From underneath the bedyou call
It wonderful; I call it crass.
Neutrinos are still without putative mass according to the Particle Data Group. Upper limits of putative mass are the bounds from the experiments to date....usually around 0.003 ev. As Wiki says, and was said here years ago, the coincidences during SN1987a at the worldwide detectors, give the velocity as ~ c to about 8 sig figs.
Why would "light speed" not work?
Light 'slows down' when going through 'stuff'.
It can get through glass faster than a diamond. It goes through empty space faster than air. Light speed is a catch-all term for many different things.
C only has 1 value, the speed of light in empty, and flat, space.
Why "light speed" is not allowed in a thread title, I have no idea, you'll have to ask the board admins.
But back to the original topic...
So by our current understanding of matter and energy, either neutrinos have mass and travel less than c, or they have no mass and can travel at c.
However, experiments measuring both mass and velocity of neutrinos have determined both that they have mass, and travel at c (within the error margin of the measurement). However, the speed measurement *could* be wrong, and they end up not traveling at c.
But, if they do move at c, and they have mass, this would certainly represent a rule-breaking particle!
Theory, meanwhile, requires them to have non-zero mass in order to explain their observed flavour oscillation, and that in turn requires them to have sub-c velocity. So it seems that we probably just need tighter measurements of both mass and velocity, so that we can distinguish between "close to" and "equal to".
My understanding was that we theororize that they have mass because they can change between thier 3 states.
Although; this might be older information, so maybe there are actually mass measurements since I heard it this way. And; I only heard it on PBS (I think it was Nova: ghost particle)
So far, neutrino flavor oscillations have all occurred in matter path/experiments. In these, the Eigenstates of the neutrinos superimpose on the matter Eigenstates, ala MSW matter oscillations, and the massless neutrino can flavor-switch. If the neutrinos are Majorana, and massive, they ought to be able to do that on their own in a vacuum, with no matter path involved. That, as far as I know, has never been seen. Until it is, there is no definitive mass, and the consistency of not violating the Law of Conservation of Lepton Family Number, which also has never been seen, seems to be the consistent guiding principle in interpreting the present results....Majorana mass means you can't tell the difference between a neutrino and an antineutrino in the same family. pete 8 sig figs is pretty good...