Neutrinos have mass. AND they travel at c.
HOW????
Rob
Established Member
Neutrinos have mass. AND they travel at c.
HOW????
Rob
Order of Kilopi
It isn't thought that they do travel at the velocity of light. They can travel at very close to c, however.Originally Posted by robross
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
Order of Kilopi
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.
Grant Hutchison
Established Member
Itīs that easy!?!
Established Member
... definitely not FTLSo now I find out matter CAN go FTL!
Established Member
See:
http://en.wikipedia.org/wiki/Neutrino#Speed
Definitely NOT faster than light.
Established Member
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!
Administrator
In the old days we didn't know whether or not neutrinos were 'matter'. They could have been more analogous to photons that carried a 1/2 spin and lepton number.
Forming opinions as we speak
Established Member
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'.
Order of Kilopi
Interesting..
Established Member
Thinking and proving are two different things. It has been very difficult to experimentally pin down the mass of the elusive neutrino experimentally. Until you prove than it has mass, you cannot take it for granted that it does. That's just how science works.
Order of Kilopi
Just adding further, how difficult is it to measure the mass of such a tiny particle (accurately) if its travelling at or very close to "C"? Also how would one measure the position/existence of any object travelling FTL if it was possible?
Established Member
Speed is not the major problem in neutrino investigations. The big problem is the ability of the neutrino to pass through matter -- detectors and even the entire Earth -- with little chance of being detected. Having no electrical charge (in addition to being small and fast) makes them very hard to detect.
Order of Kilopi
yes thanks, i was trying to point out that because they are so small that any form of detection would surely change the precision of the measurement taken of the mass, speed and position, as in the uncertainty principle.
Administrator
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!
Vulcan Administrator
"light speed" doesn't work, but "c" does.
Everything I need to know I learned through Googling.
Banned
This is the second time in this thread where I need some explanation of comment.. please ?"light speed" doesn't work, but "c" does.
What is this about ? Are you referring to the search function?
Thanks Alainprice... you may have just answered me..
Order of Kilopi
Actually; I believe it was in reference to what words work within thread titles.
I do agree Alainprice's answer does fit as well.
But; maybe it's extremely intelligent board software too.
Established Member
My original *thread* title was written hastily. It was "So now I find out matter CAN travel FTL" when I really had meant "c", not FTL. I was not able to change the thread title after I saved it, I could only change the title of my first *post*. I asked the mods to change the thread title, but they were unable to change "FTL" to "light speed", but they discovered that changing "FTL" to "c" did work.
Why "light speed" is not allowed in a thread title, I have no idea, you'll have to ask the board admins.
Rob
Order of Kilopi
So the answer is that light can never travel at "c", although it can travel FTL, as alainprice noted above.
Established Member
Why would "light speed" not work?
Established Member
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.
Established Member
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!
Rob
Order of Kilopi
Well, experiments show that they have masses very close to zero, and velocities very close to c: the error margins are small, but accommodate non-zero mass and sub-c velocity.
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".
Grant Hutchison
Order of Kilopi
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)
Order of Kilopi
Yes, that's the flavour oscillation I mentioned above.
Grant Hutchison
Member
By the original measurements for the neutrino's speed (by viewing the interactions of neutrinos that were created from decayed pions), that known to be repeated using MINONS detectors, we only know that there is only a very high uncertainty that the neutrinos don't travel at FTL, or at c' according to Rob's resent post changes, also, in measurements for the speed of neutrinos from a supernova, the detected results indicated that those neutrinos were travlling at c'.
For now at least, the neutrino's mass is undefined, and can not be measured by its speed.
----
If I repeated a previous post, I apologize.
Last edited by chi22; 2009-May-18 at 08:54 PM.
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