[QUOTE=only_human;272692]Since that isn't the current belief, what compels nutrinos to always travel everywhere in a hurry?[/QUOTE]For any given impulse of kinetic energy, the low mass of a neutrino will be propelled at a higher speed than the higher mass of some other particle. From a neutrino's POV, every kick is a BIG kick.

[QUOTE=only_human;272692]Why aren't there any slow nutrinos?[/QUOTE]

[QUOTE=davieddy;272695]I guess there may be a few slow neutrinos, but that they are even
less detectable than energetic ones.[/QUOTE]

[QUOTE=cheesehead;272727]For any given impulse of kinetic energy, the low mass of a neutrino will be propelled at a higher speed than the higher mass of some other particle. From a neutrino's POV, every kick is a BIG kick.[/QUOTE]

OK, thanks; I'm now finding that Cosmic Neutrino Background (CNB, CvB, relic neutrinos) discussions have the most information about existence and potential detection of slower neutrinos.

[QUOTE=only_human;272740]OK, thanks; I'm now finding that Cosmic Neutrino Background (CNB, CvB) or relic neutrinos discussions have the most information about existence and potential detection of slower neutrinos.[/QUOTE]
I'm off to hunt down some dark matter.
Or was that entropy?
More C[SUB]2[/SUB]H[SUB]5[/SUB]OH required.

David

[QUOTE=davieddy;272741]I'm off to hunt down some dark matter.
Or was that entropy?
More C[SUB]2[/SUB]H[SUB]5[/SUB]OH required.

David[/QUOTE]You're drinking ethanol?

[QUOTE=Jwb52z;272779]You're drinking ethanol?[/QUOTE]

Yep (I hope).
Tried meths but it damaged my eyesight.
Might die in a few years.

David

[QUOTE=only_human;272692]Ok, so the current conundrum aside, originally nutrinos were considered to travel at the speed of light because they were believed to have no mass. Since that isn't the current belief, what compels nutrinos to always travel everywhere in a hurry? Why aren't there any slow nutrinos?[/QUOTE]

As cheesehead notes, since the mass - even if nonzero - is still very small, even at modest energies neutrinos will be traveling very close to the speed of light. Couple the tiny mass with their exceedingly weak interactions with "normal" (that is, baryonic) matter and the fact that they are disproportionately produced in a smallish set of physical interactions (e.g. nuclear reactions certain types of radioactive decay), and that would appear to bias things toward the high-energy spectrum, as compared to, say, photons. (In terms of neutrinos produced in the present-day universe - ones left over from the big bang are a whole different can of worms - see link below).

And yes, there is also a large detection-side bias toward high-energy neutrinos.

It would be interesting to see some analysis regarding the expected neutrino energy spectrum in the universe - doing just a quick web-search I managed to find [url=http://www.astro.bas.bg/AIJ/issues/n10/01_DKirilova.pdf]this pdf[/url] which models neutrino-spectrum evolutions based on flavor-change and standard big bang cosmology - it notes in particular that "cosmological neutrinos are expected to have today extremely low energy".

[QUOTE=ewmayer;272805]

And yes, there is also a large detection-side bias toward high-energy neutrinos.

[/QUOTE]

That's quite an understatement. IIRC, conversion of Cl to Ar (in the classic "dry cleaning fluid" type experiments) has a neutrino energy threshold around 800keV. Later gallium experiments got down to around 250keV. But neutrino masses are a fraction of a single eV, making even the lowest energy neutrinos we can detect ultra-relativistic.

Because the natural energy scale of weak interactions is so much higher than the neutrino mass, the only way we might detect non-relativistic neutrinos (any time soon) is through their cosmological impacts.

--Scott

[url]http://ca.news.yahoo.com/video/tech-22186835/invisibility-shield-may-soon-see-combat-26715834.html[/url]

Cloaking Magnetic Fields: First Antimagnet Developed
[url]http://www.sciencedaily.com/releases/2011/09/110922192056.htm[/url]

Tevatron. 1983 -- 2011. RIP
 

[url]http://www.bbc.co.uk/news/science-environment-15079119[/url] has a very nice obituary.

catchiest pop song ever scientifically crowned:

[url]http://ca.news.yahoo.com/science-hails-champions-catchiest-pop-song-ever-111119672.html[/url]