Talk:Neutrino/Archive 2

Archive 1

Archive 2

Archive 3

The origins of the Universe

It has been suggested that neutrinos may have been the main type of matter created during the Big Bang, and that the visible matter now present in the universe may have been created through radioactive neutron decay.

Roadrunner 18:45, 27 Apr 2004 (UTC)

That is completely untrue. Have you not heard of Normus Dmitri's newly composed theory?

The trouble with this "neutrino's created everything we see" theory is the usual one: find something we don't understand in cosmology/particle physics, hypothesize that it's got God-like properties and created everything, and then claim we just have to figure out how it works (usually with a request for funding added). I wouldn't think too highly of that theory, it's the same old 'I-can't-figure-this-out-so-it-must-be-God' issue a lot of scientists have nowadays. (The Higgs Boson and Dark Matter are also the really hip thing right now).Your quote might of course have been from a journalist who didnt really understand the physicist he was talking to.Crusty007 (talk) 18:58, 15 September 2010 (UTC)

Handedness

Could someone be more explicit about the neutrino handedness? I.e., if a neutrino is emitted from an interaction towards an observer, does it appear to rotate clockwise or anticlockwise?

As the article says, the neutrino is left-handed. This means that if you use your left hand's thumb to indicate the direction of motion, the other fingers (when curled) will indicate the direction of rotation. Therefore, the answer to your particular question is "clockwise". Yevgeny Kats 04:17, 6 February 2006 (UTC)

An explanation as simple and short and understandable as this, should go right into the article! SBHarris 20:28, 12 February 2008 (UTC)

The Handedness section needs to be clarified. As it stands, it confuses helicity and chirality. Neutrinos can have any helicity, since we can boost to a reference frame as to reverse its motion. All neutrinos, however, have left handed CHIRALITY in ANY reference frame. -DCrow —Preceding unsigned comment added by 70.95.189.136 (talk) 11:02, 16 March 2010 (UTC)

a new view of the neutrino

It seams that there is a lot of skepticism and confusion about this topic. Neverthless there is some experimental evidence in the nuclides data together with macroscopic data such as the universal temperature level and the decrease of the revolution time around the sun that surprisigly give a unique responce. For readers that are interested and have some practice of italian please look at the two poblications in :

http://www.aidic.it/italiano/divisioni/process/process.htm

English readers can find a translation of the first paper in

http://www.3ip.it/DONATI/paper2.

Gianni Donati

gia.donati@tiscali.it —The preceding unsigned comment was added by 200.88.197.38 (talk) 15:53, 5 May 2007 (UTC).

The second link has died and is rotting away now...you might want to update it.Crusty007 (talk) 19:14, 15 September 2010 (UTC)

Solar vs. Cosmic

What is the difference between a cosmic neutrino and a solar neutrino? —Preceding unsigned comment added by 76.15.95.46 (talk) 04:05, 24 October 2007 (UTC)

The most important difference is their source. However, as for being able to determine that, their energy is the most significant difference. Galactic neutrinos have more energy than solar neutrinos and extragalactic neutrinos can have even higher energies. Ben Hocking ^{(talk|contribs)} 12:49, 24 October 2007 (UTC)

That, and the fact that we can do more fun experimental stuff with solar neutrinos because we know a) where they came from, b) how long it took them to get here, and c) how they where created (at least we think we do). Because of this we can theorize more about solar neutrinos and design experiments for those theories. Neutrino oscillation is (currently) impossible to detect from cosmic neutrinos simply because they come from all over the place.Crusty007 (talk) 19:28, 15 September 2010 (UTC)

Negative Mass

The electron neutrino must have negative mass, and I will show you why. Let's say that the proton mass is 1836, the neutron mass is 1839, the electron mass is 1, and the neutrino mass is X. In order for mass-energy to be conserved, X must be a negative number. That would make the neutrino an example of exotic matter.--Luke Elms 04:32, 27 June 2008 (UTC)

Neutrons (1839) --> protons(1836) + electon(1)+ neutrino. That means the neutrino can have any mass up a large fraction of an electron. For reasons of momentum conservation, it's always less than the whole thing. But I don't see where your problem is. SBHarris 00:44, 2 July 2008 (UTC)

Me neither. Proton and electron weigh less combined than a neutron. The anti-neutrino has part of the rest (IF it has mass). You can think of it (for simplification only) as the neutron made up internally of a proton and an electron, and a very tiny piece of rope binding them together. When the rope goes PLOINK! and breaks, you get beta decay, with the proton and electron moving away from each other, they hate being close. The anti-neutrino would be the equivalent of the rope breaking away, it would have speed, and possibly some mass...those two properties together are the total energy of the anti-neutrino.We only can tell the rope is there because we can detect it when it slams into something else at incredible speed and dont find one just lying around to put on a scale and weigh it.HTH,Crusty007 (talk) 20:27, 15 September 2010 (UTC)

Actually the "missing" mass/energy is not due to neutrinos, but rather to the fact that protons and neutrons are made of different quarks. For example, a proton is made of two up quarks and one down quark. A neutron is made two down quarks, and an up quark. Different quark, different masses. However, the mass of the proton/neutron is not simply due to the mass of each quark, there are other reasons too, but I'm afraid I can't explain them as I don't really understand them. Headbomb {ταλκ – WP Physics: PotW} 05:27, 27 June 2008 (UTC)

You are substituting one incomplete answer for another I'm afraid. We don't really know why quarks have different mass; we haven't got a clue what's inside them. Crusty007 (talk) 20:27, 15 September 2010 (UTC)

Decay rates?

Is this worth mentioning? It is postulated that neutrinos have some effect on the rate of radioactive decay. It appears to have some further valid citations, though perhaps they need a bit of further research. —Preceding unsigned comment added by 217.169.15.243 (talk) 17:44, 21 November 2008 (UTC)

It's a really interesting idea, and it has gotten attention. However, all we have so far is a single speculative preprint on the arxiv, not even a peer-reviewed publication. That's just not enough to justify inclusion in the general article on neutrinos. If there's a section somewhere that specifically covers the constancy of nuclear decay rates, it might be worth mentioning. --Amble (talk) 18:39, 21 November 2008 (UTC)

Here's more. According to this article, it's been published in Astroparticle Physics, Nuclear Instruments and Methods in Physics Research and Space Science Reviews. 81.187.27.106 (talk) 16:48, 24 August 2010 (UTC)

People vs Square Metres of Earth

So 50 trillion neutrinos are passing through me each second, but only 64 BILLION are passing through each metre of the earth? Obviously a typo but without knowing the correct figure I can't exactly correct it.

"and more than 50 trillion solar electron neutrinos pass through the human body every second." "Every second, about 65 billion (6.5×1010) solar neutrinos pass through every square meter on Earth that faces the sun." —Preceding unsigned comment added by 80.193.149.95 (talk) 13:14, 12 July 2009 (UTC)

It should be 65 billion per cm² for the solar neutrino flux. I fixed this but have not checked the number for the "human body", which would involve an assumption on the average area of a human. --Blennow (talk) 14:13, 5 August 2009 (UTC)

Yes. Probably better not to go there, for this reason. It also depends on the body's orientation to the sun. I've seen estimates also of how may neutrinos per volume are contained in the body any given instant, a figure which interestingly is more or less constant over time but not dependent on body orientation (think about it). But is still dependent on volume, which varies from person to person, even if not from body position to position. A figure per cm³ is just the figure per cm²/c = about 2.2 neutrinos/cm³. A 70 kg person with the specific gravity of water would always contain 150,000 neutrinos at any one time. Just passin' through. SBHarris 00:15, 28 November 2009 (UTC)

The article still states that there are 50 trillion neutrinos which pass through the human body every second. The referenced source is an MIT News article from 2007 which does not in turn state any references or citatitions for this information. In order to avoid some of the inconsistencies regarding body mass and orientation, I would suggest modifying the reference to address the surface area of the Earth facing the sun. 165.127.8.254 (talk) 16:59, 3 November 2010 (UTC) User:guest

Neutrinos are so penetrative that it doesn't matter if it's the area facing the sun or not! Orientation DOES matter if you work in neutrinos per second. If you're interested in how many the body contains at any instant, that's body-volume-dependent but orientation-independent.SBHarris 20:50, 3 November 2010 (UTC)

Yes to 165.127.8.254 and yes to User:Sbharris. We must also say that the flux is through a orthogonal surface to the flux. "the Earth that faces the Sun" is OK for this and the next sentence explain in simple words "no matter the surface" but without saying exactly this. --Rical (talk) 09:56, 4 November 2010 (UTC)

Neutrinos and their impact on the Earth's core temperature

In the film 2012 that started showing a few days ago, neutrinos were shown causing the Earth's core temperature to rise. Can someone comment on the validity of this? —Preceding unsigned comment added by 203.117.33.24 (talk) 14:46, 15 November 2009 (UTC)

Short answer: Movies are fiction, not science. Dauto (talk) 15:16, 15 November 2009 (UTC)

That movie, "2012", is why I looked at this article. I thought neutrinos were massless, didn't know there was controversy. But when the movie hit me with solar neutrinos as the "cause" of something I wondered who the producers thought their target audience was. Even if neutrinos could "do" something, why would they cause destruction of the Earth from the inside out?Dangnad (talk) 20:05, 20 November 2009 (UTC)

The answer is don't trust what you hear in poorly-thought out bad science fiction movies. They just followed the usual "take something that sounds complicated, say that something that can't happen happens, then give a nonsense explanation for it" formula. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 22:51, 20 November 2009 (UTC)

In that (and any) distaster movie's defence, if they depicted an entirely scientifically accurate way of the world coming to an end, not only would the concepts go completely over the head of most viewers, but the movie would be incredibly long and dull. Anyone with any basic knowledge of science know that it works in time scales that are massive in comparison to what most people consider a long time (millions of years in comparison to say, a decade or two). That does not make scientific inaccuracies in order to make a movie, you know, enjoyable, cause it to be a "poorly-thought out bad science fiction movie."

I suggest you keep your naive opinions to yourself and simply explain the facts - that the movie exagerates or invents the science to make an enjoyable movie for the general public. Perhaps if a scientist ever moves into producing or directing a movie then they can create one so esoteric that just the scientific community can enjoy its authenticity, but that doesn't make your average disaster movie bad. —Preceding unsigned comment added by 80.195.30.79 (talk) 23:49, 27 November 2009 (UTC)

It doesn't help that that particular film is also founded on a load of garbage, but that's besides the point. No, neutrinos could not cause the planet's core to heat; they pass through almost all matter, and even if they SOMEHOW lost that property, they would affect the surface, not the core. On a side note, I would ask you to refrain from possibly insulting comments like your "keep your naive opinions to yourself". -RadicalOne---Contact Me 00:01, 28 November 2009 (UTC)

I'm just revisiting my original post on "2012". Who is this "naive opinions" guy. Sounds to me like the movie was directed to him and like-minded people...and he can't even spel exagrates. I've given the movie some more thought and have decided if they had led off with an off-the-wall explanation like "curlywhumps" ejected from Sol will destroy the Earth then that silly movie would've been more enjoyable. When they start off with a completely implausible scientific explanation as neutrinos then that ruins the movie for most of us with just a bit of scientific background.Dangnad (talk) 03:03, 16 June 2010 (UTC)

I'm in the field, and found that movie okay. It's an interesting bit of speculative fiction. The idea of sterile neutrinos is completely open - that they don't interact at all(hence, sterile) is the part thats missed here. But the idea that neutrinos might oscillate into something other then the 3(really two from our perspective on earth) flavors is not terribly insane. Having them heat up the core, but somehow not effect the surface - now theres crazy talk for you. They also didn't mention all the main neutrino observatories, which also made me sad. But lets be fair - it wasn't intended by some piece of accurate science fiction. Give them credit for even bothering to try and make some parts of it reflect real science. That they then decided to have them kill us all is rather required for the premise of the movie :) Simon.p.hastings (talk) 20:04, 22 June 2010 (UTC)

Merge

Taking a look at Antineutrino, I can't help but feel this would best be presented as a section in this article. There's really not much to say about antineutrino other than talk about their helicities and wheter they are Majorana or Dirac fermions. Headbomb {talk / contribs / physics / books} 15:05, 8 March 2010 (UTC)

Merge. I agree. Unlike the antimatter counterparts of familiar matter, neutrinos and antineutrinos are equally ghostlike and removed from everyday life. The distinction is important but highly technical, and it would serve the average reader better to have the two articles combined. By reading about neutrinos first, the reader will know just about everything there is to know about antineutrinos. Conversely, knowing the differences between neutrinos and antineutrinos enhances the neutrino article without adding too much to its size. CosineKitty (talk) 16:15, 8 March 2010 (UTC)

Merge. Agree. Particularly as it appears that neutrinos have rest-mass, which means that neutrinos and antineutrinos are the same particle (to convert one to the other, simply go faster than it's going, and in that frame it changes helicity). It's true that the things are going so fast that we hardly ever get the chance to see them in the frame which changes their helicity, so reactions involving them make them seem to be two different particles. But that's a reason to have two sections in one main article. SBHarris 20:51, 8 March 2010 (UTC)

Surely a neutrino can't be converted into an antineutrino by a Lorentz transform? Flipping helicity does not convert to an anti-particle. --Michael C. Price ^talk 03:30, 9 March 2010 (UTC)

A majorana neutrino is its own anti-particle. It is not known yet wheather neutrinos are majorana or not. Dauto (talk) 04:46, 9 March 2010 (UTC)

Well, "Majorana neutrino" is a just a fancy way of saying that the only difference between this particle and antiparticle IS the helicity. Which would indeed mean that a Lortentz transform would convert one to the other. And the idea seems a reasonable proposal, since otherwise, there must be yet another property we haven't found, that distinguishes neutrino from antineutrino of a given flavor, and is NOT the helicity, since there's no question that a Lorentz transform DOES flip helicity for a massive particle. It would have to be yet another yet-undiscovered quantum number. Sure, it might be there, but Occam at this point says "no." Not only that, but if there's this other new quantum number that defines "anti-ness" in neutrinos, then it's theoretically possible to have neutrinos and antineutrinos of the "wrong" helicity. Yet, these have not been observed. Why not? Neutrinos came in all energies, and something, somewhere a long way away and moving fast, should have made some spinning the "wrong way" from our viewpoint. Where are they? SBHarris 05:12, 9 March 2010 (UTC)

Perhaps we don't see these flipped helicity neutrinos because the neutrinos we do detect are primarily from the Sun and terrestial sources, which aren't moving fast?

Switching to chirality, rather than helicity, some theories have right-handed neutrinos with v.large rest masses, which explains why we don't see them. Simple theories are not always correct - as we found out with minimal SU(5).--Michael C. Price ^talk 06:01, 9 March 2010 (UTC)

While there are strong arguments for the neutrinos to be Majorana fermions, it would be safe to wait until the neutrinoless double beta decay searches finds something tangible before saying conclusively that they are. We could ask another question. Namely, "If neutrinos are indeed Majorana fermions, then where are the neutrinoless double beta decays we should find?" Headbomb {talk / contribs / physics / books} 05:48, 9 March 2010 (UTC)

Anyway, it seems we have consensus for the merge. I don't have much time right now, but I should be able to do it by tomorrow (unless someone beats me to it). Headbomb {talk / contribs / physics / books} 05:50, 9 March 2010 (UTC)

Merge. While on the subject there are three additional Wiki articles and I do not know why they exist. The electron neutrino, muon neutrino and tauon neutrino articles all belong in this Neutrino article under the existing heading of "Types of neutrinos"(Section 2.1). While there may be some validity to antineutrinos as a separate classification, there is none for these. Those articles even repeat some of the same information in this Neutrino article. -- 71.143.181.118 (talk) 07:32, 23 March 2010 (UTC)fhj52

I've begun the process of merging the articles, per consensus. I think it's interesting they think neutrinos and anti-neutrinos might be the same particle. Noone's ever seen them annihilate each other, have they?--Robert Treat (talk) 20:56, 8 April 2010 (UTC)

Thanks for taking the lead. And yes, no one has ever seen neutrinos annihilate (neutrinos are pretty hard to detect to begin with). However, searches for neutrino annihilation have begun in recent years. See double beta decay for an overview. Headbomb {talk / contribs / physics / books} 22:26, 8 April 2010 (UTC)

I've cut content from antineutrino and pasted it onto neutrino, however a bot has interpreted my edits to the former as vandalism and restored its content --Robert Treat (talk) 22:49, 10 April 2010 (UTC).

Thanks for your work in merging the articles. I think all that's needed is to make antineutrino a redirect here. I've now done that, and I don't think the bot will object this time. :-) --Amble (talk) 00:45, 11 April 2010 (UTC)

User:Wintonian is not a bot, as far as I know. Rich Farmbrough, 20:05, 12 April 2010 (UTC).

Right you are. In any case, the status of the two pages is clear now. --Amble (talk) 21:19, 12 April 2010 (UTC)

However, searches for neutrino annihilation have begun in recent years. Before getting to the end of the post, I had thought about the annihilation of on-shell neutrinos, and thought "How the hell are they gonna search for this?" :-) A. di M. (talk) 18:40, 4 June 2010 (UTC)

Detecting nuclear weapons via electron antineutrinos

It's been proposed to use electron antineutrinos as a way to detect the global distribution of uranium and thorium reserves.[1] But can detection be made highly directional so that individual nuclear weapons can be visualized (by decay of tritium or uranium decay products) in a way that cannot be blocked by any matter? Is it possible that such a detector has already been in operation for some decades? Wnt (talk) 05:06, 15 April 2010 (UTC)

Possible, but unlikely. Purified fissile material isn't very radioactive, thus it emits very few neutrinos just sitting there in bombs. Tritium is highly radioactive, but the neutrinos are always less than 18.6 kev, which is just 1% of the current lower limit of neutrino energy detection (at least in the open literature). So how would you even do it?

If you had a working neutrino detector for nuclear-reactor fission associated neutrinos that was PORTABLE (small enough to go on a BIG ship) you'd be using it to hunt for the much higher neutrino emission of the reactors powering "boomer" ICBM subs (and also attack subs). It seems to me that this is the technology closest to being physically possible with today's technology, but it's still a formidable task. You need good directionality to look for subs, and the problem is that even if you solve the detection problems, anything that makes it though 1000 ft of water is going to be hard to collimate with any concentration of material you're likely to be able to keep afloat. SBHarris 18:41, 18 April 2010 (UTC)

attention needed for mass table

The table showing masses doesn't agree with the later "mass" section, by orders of magnitude. The latter states that 50ev was a hard upper bound, but the table shows 50 Mega-ev! The orders of magnitude differences between the 3 generations in the table doesn't match the text which gives small numbers for the differences of the squares. I don't think I can put an "expert needed" banner that refers to just a table?
—Długosz (talk) 16:02, 23 April 2010 (UTC)

Afaik the table just has very old numbers. More current figures should be about 0-240meV, 9-240meV, 40-280meV if I understand the constraints correctly. I don't want to edit the table without having a source specifically giving masses rather than differences of squared masses though. 213.243.163.221 (talk) 13:44, 13 July 2010 (UTC)

Confusing Antineutrino Wording

I'm quite the opposite of an authority on this subject, but the sentence "Antineutrinos interact with other matter only through the gravitational and weak forces, making them very difficult to detect experimentally." in the Antineutrino section seems to imply that this behavior is different from that of the Neutrino, which isn't explicitly stated. Maybe this could be removed, or amended to "Antineutrinos, like Neutrinos, interact etc."Pfhortipfhy (talk) 02:14, 4 June 2010 (UTC)

Done. Dauto (talk) 15:09, 4 June 2010 (UTC)

New mass source attention

BBC: Neutrino 'ghost particle' sized up by astronomers, before a scientific article that is going to be published in the Physical Review Letters l8R. Note that the scientists report some very unusual and unexpected assymetries between neutrinos and anti-neutrinos... if they exist. Rursus dixit. (^mbork³!) 06:58, 23 June 2010 (UTC)

The Minos result is certainly very interesting, but its statistical significance is not high enough to be definitive. --Amble (talk) 07:55, 23 June 2010 (UTC)

Fourth Flavor of Neutrino?

Perhaps this article needs to be shown proven as true or "debunked" so that things will be made clear: http://www.sciencedaily.com/releases/2010/11/101102185722.htm —Preceding unsigned comment added by 71.237.241.12 (talk) 13:53, 28 January 2011 (UTC)

So what is a neutrino exactly...?

This article seems to be very well written, but for someone who is not too knowlegable in science (like me), it doesn't describe what it is or what it does very well. To the previously uninformed, it seems like a while lot of scientific gibberish. What do neutrinos actually do? 68.161.120.42 03:08, 15 November 2005 (UTC)

They don't do anything. They're produced by weak interactions (like beta decay) and then they fly away through the universe, passing right through matter like it's not even there. You should picture them as being like an electron without any charge and almost no mass. -- Xerxes

If neutrinos didn't do anything, then they'd be impossible to to detect.--Zerothis (talk) 19:17, 30 August 2008 (UTC)

To previous user: It's not gibberish. It is complicated and there is no easy way to de the subject justice if someone doesn't have a basic understanding of particle physics. If you need to know something beyond the fact that they are small and neutrally charged, you will have to research other articles to build a foundation of understanding.--Dr.Worm 05:55, 25 April 2006 (UTC)

As wikipedia is aimed at readers with an average level of knowledge (i.e. lacking advanced knowledge of particle physics it might be useful to include a simplified description of a neutrino. Similar to the school level description of other particles e.g. "protons are made of 2 up quarks and one down quark." the most obvious questions to answe would be: what are neutrinos made of and what their physical properties are. Perhaps if a very simple description was given in the introduction with the more detailed description later in the article. 22:32, 21 August 2006 (UTC)

You can't get a description because despite all the theory, no one has ever seen one and no one knows what they are. The Ancients' question "How many angels can sit on the head of a pin" asks whether angels occupy space or, in modern terms "have mass." Nutrinos are part of the modern Cosmology and, like angels, apparently don't have mass and are very elusive. Whether any of this is actually real or not is a theological question. Have Faith! missaeagle —Preceding unsigned comment added by Missaeagle (talk • contribs) 16:10, 19 May 2008 (UTC)

As described in the article, "Neutrinos are certain elementary particles. Traveling close to the speed of light, lacking electric charge, and passing through ordinary matter almost undisturbed, their detection is extremely challenging. They were long thought to be massless, but are now known to have a very small but non-zero mass." This seems to be a pretty simple description, and gives the reader no more or less understanding of the subject than "protons are made of 2 up quarks and one down quark.". Honestly I don't think an average reader really knows what an "up" or "down" quark is either. --7 December, 2007 —The preceding unsigned comment was added by 69.205.19.211 (talk) 01:05, 8 January 2007 (UTC).

Honestly, most scientist haven't got a clue as to what an "up" or "down" quark is either. They're just used to using them as abstract constructs, as opposed to normal people. That doesn't mean they actually exist, which some of the more knowledgable physicists will actually tell you. Crusty007 (talk) 20:34, 6 March 2009 (UTC)

1. )Is the source of neutrinos inexhaustible? What is their end state? A good explanation and better idea of what neutrinos are or are not can be found at R. Carezani's Autodynamics.org website. Good hunting...JCatCCAD/31Jan10. —Preceding unsigned comment added by 165.95.9.114 (talk) 00:18, 1 February 2010 (UTC)

Unsigned, according to the Autodynamics entry, that theory states that neutrinos don't exist at all. Długosz (talk) 16:08, 23 April 2010 (UTC)

64.71.92.235 (talk) 01:29, 7 February 2011 (UTC)jc-at-ccad/2-6-11 .....And going thru Carezani's analysis of the Kamiokande data is difficult to see why there should be a neutrino. (I know the rest of his autodynamics math is questionable).

Mass

The discussion about the meaning of "neutrino mass" is probably incomprehensible to Wikipedia readers who are not versed in quantum mechanics. It is necessary for a discussion at this level? Should it be moved to the mass page? Could it be replaced by something more comprehensible to "mere mortals"? Jorge Stolfi 18:41, 23 Mar 2004 (UTC)

I agree that the information on neutrino mass is "incomprehensible" to folks like me (biologist). I simply copied what is on the Standard model page. I think there has to be something about neurino mass on this page, maybe how it relates to the experimental techniques that are used to detect neutrinos.

There is also the question of what information should be in Wikipedia and what information should be in a physics textbook at Wikibooks. JWSchmidt 19:07, 23 Mar 2004 (UTC)

It's not only incomprehsible. It's also wrong....

The upper limits for the mass of the neutrinos are shown in the table. Mass is really a coupling between a left handed fermion and a right handed fermion. For example, the mass of an electron is really a coupling between a left handed electron and a right handed electron, which is the antiparticle of a left handed positron.

(In the case of neutrinos, there are large mixings in their mass coupling, so it's not accurate to talk about neutrino masses in the flavor basis or to suggest a left handed electron neutrino and a right handed electron neutrino have the same mass as this table seems to suggest.)

I've never heard anyone suggest this

Agreed, the two paragraphs above are non-sense.

They may be incomprehensible, and weird even to those who do understand them, but they are true. -- SCZenz 18:38, 27 November 2005 (UTC)

I know the usual theories on the origin of mass, but I insist: if the statement (in the second paragraph) is not wrong, it is clumsy and misleading. Neutrino masses can be, and are, expressed in flavour "basis" (and vice versa), which is what makes flavour oscillations possible. I don't see how a large mixing angle would make this inaccurate. I would appreciate if you explained.

can someone explain what's the effect of neutrino's having mass. Is this capeable of slowing down the voyager?, or does it mean that our sun is getting lighter? would it it mean that our universe would collapse, or perhaps something else. Because i dont understand what's the fuzz, tell me what's the happenning, what about a neutrino having mas ?? Please in a not to scientic language i'm just a normal wiki reader kid.

All the things you suggest are wrong, except that the Sun does lose mass. However, it primarily loses mass due to the solar wind. The small amount of mass lost due to neutrinos would be the same regardless of whether the neutrinos have mass themselves.

Here are some implications of massive neutrinos: The universe is filled with unseen neutrinos, so knowing that neutrinos have mass means we know a bit more about dark matter. Since neutrinos are hot dark matter, they have some implications for galaxy formation and models of the young universe. Neutrino mass solves the solar neutrino problem, which was that the number of neutrinos observed coming out of the Sun was less than the amount predicted by theories of stellar fusion. The missing neutrinos have oscillated into other flavours. It adds seven new parameters to the Standard Model of particle physics: three mixing angles and one CP-violating phase in the MNS matrix, and three masses. Measuring these new parameters is a major challenge for 21st Century physics. -- Xerxes 16:21, 5 April 2006 (UTC)

For the beginner, I found this informative: http://video.google.com/videoplay?docid=-8767749306895504516 Hope it helps. P.S. It would be nice to have an "introduction to neutrinos" page like they have for M-theory/Brane theory.72.78.6.125 (talk) 09:11, 25 December 2007 (UTC)

Mass Delta Claimed to Come From the MINOS Experiment is Inconsistent with the Cited Reference

The article says |Δm²
₃₂| = 0.0027 eV², but the reference cited actually gives a value of 0.0031 eV² +/- 0.0006 eV² (statistical uncertainty) +/- 0.0001 eV² (systematic uncertainty). While the value given is within the range cited in the source, I can see no reason for this specific figure. Unless a reason to lowball the value can be provided (with a reference), it should be changed to reflect the reference. Furthermore, in the interests of accuracy, the error ranges for these Δm² values should be added.

-- Karatorian (talk) 22:31, 16 April 2011 (UTC)

Pressure or Density

The core does not have a pressure of 10¹⁴ g/cm³, this is in the wrong units. The density of the core is this value. I'm not sure what the pressure is, hence why I haven't changed anything. ANS BY SACHIN;;>pressure is outer force by any thing, in other words, act the force on unit area but density is the selfproperty of any matter or the quantity of maas in unit volume in any matter.we can increase the density by pressure but pressure is incresae by force. — Preceding unsigned comment added by 42.108.35.19 (talk) 04:03, 10 July 2011 (UTC)

Do neutrinos exist outside of atoms?

I was told that everything was made up of atoms. And that sub-atomic particles exists inside an atoms and they are the smallest things possible. But is neutrino inside an atom and is it considered a sub-atomic particle? —Preceding unsigned comment added by 69.165.149.165 (talk) 04:36, 31 August 2010 (UTC)

The usual place to ask these questions are at the reference desk. However, you should find your answer at in the article on matter (read everything up to and including "quarks and leptons definition"). Short answer, neutrinos are subatomic particles, just like electrons are. Headbomb {talk / contribs / physics / books} 20:40, 31 August 2010 (UTC)

Sub-atomic particles are not necessarily the smallest thing possible: Both the proton and the neutron are larger than the electron (for which no lower size limit is known). The neutrino is not part of an atom, it may be inside an atom (and usually for no more than about an attosecond within one and the same atom, while it's flying through the atom), or outside, but unlike e.g. the electron it is not part of an atom. Icek (talk) 20:37, 22 September 2011 (UTC)

Alteration of nuclear decay rate section

The reference to radiometric dating here is worded poorly, and leans towards unsupported conjecture. Though since one of the only articles dealing with this can be found at a creationist website perhaps the framing of the significance of the variability of decay has been POV. 137.111.13.200 (talk) 00:57, 23 September 2011 (UTC)

CERN discovery

From here: Antonio Ereditato, spokesman for the researchers, said: “We have high confidence in our results. We have checked and rechecked for anything that could have distorted our measurements but we found nothing.

Just wondering what the basis is for the words "very controversial" in the lead. Jprw (talk) 11:56, 23 September 2011 (UTC)

It is a single experiment. Even the authors say that others need to check their work for systemic errors. It also directly contradicts other experiments that show neutrinos travel at the speed of light or less. And if true, it would require a fundamental re-think of physics. The debate should be in the article, but not in the opening paragraphs, which should detail the accepted knowledge. Ashmoo (talk) 12:42, 23 September 2011 (UTC)

It's a single result. Other experiments have not shown such an effect - in one sense, it's a question if you believe this one experiment or the X other experiments. The physicist community is rather skeptical of the result at the moment, though open. The claimed result is 6-sigma, but the paper deliberately states that they need to explore the systematic effects, and refrains from jumping to conclusions. Would that Wikipedia would do the same. Seleucus (talk) 15:13, 23 September 2011 (UTC)

Edit request from Mh40, 26 September 2011

I oppose the edit proposed below. (I am posting this above because my comment does not appear when posted below.) A single experimental result that even its own authors do not accept unreservedly, and for which broad skepticism has been expressed amongst the physics community, does not carry sufficient weight. That is not how science works. The article discusses the new experiment adequately in the body. Spectacular, tentative results do not belong in the lede. Strebe (talk) 02:04, 26 September 2011 (UTC)

my request to edit is concerning the "speed of neutrinos" as the article indicates that neutrinos were generally assumed to travel at the speed of light, a statement that has lost its credibility after the Italian experiment that was carried out this month has showed that neutrinos travel faster than 299,792,458 meters per second.

http://www.nature.com/news/2011/110922/full/news.2011.554.html

— Preceding unsigned comment added by Mh40 (talk • contribs) 01:29, 26 September 2011

Not done for now: Thanks for the suggestion, but I agree with Strebe above. Those results will merit inclusion in the lede if they gain the acceptance of other physicists. See also Wikipedia:Recentism. Adrian J. Hunter^{(talk•contribs)} 11:01, 26 September 2011 (UTC)

Faster than the speed of light?

In the neutrino detection section it mentions "charged particles moving through a medium faster than the speed of light". Is this really correct? I thought light always moves faster than anything else in a medium.

The speed of light in a medium can be slowed than the speed of light in a vacuum. Although photons are still individually moving at the speed of light, they are being absorbed/emitted/reflected/etc. by the medium so that the wave propogates as a slower speed. This causes effects like cherenkov radiation. See Speed of light#Interaction with transparent materials. -- SCZenz 19:54, 20 March 2006 (UTC)

In other words, the speed of neutrinos is barely affected by the medium it travels through and appear to travel at the same speed regardless of the medium. On the other hand, light can be slowed down by the medium it passes through. In the case of this supernova , light had to pass through inter-steller medium that probably slowed it down. While the neutrinos maintained their velocity, thus arriving earlier. — Preceding unsigned comment added by 70.253.144.119 (talk) 18:20, 27 September 2011 (UTC)

A half-answer, :-)

Neutrinos are not charged particles so Cherenkov radiation is irrelevant. What matter density is neccesary before neutrinos travel at light speed in the corresponding medium? How much is red shift due to electromagnetic interaction? Cave Draco 01:36, 5 October 2006 (UTC)

The neutrinos aren't detected via cherenkov radiation. Rather a reaction like

$\nu +p\to e^{+}+n$

happens, and then the positron (e⁺) is detected via cherenkov radiation. Does the article not explain this well? -- SCZenz 01:40, 5 October 2006 (UTC)

Special relativity says that there is a maximum speed, and postulates that the speed of light is that speed. But there is speculation that the photon has a nonzero rest mass, and this would lead to the speed of light being slightly less than the absolute maximum given by special relativity (see for example http://prl.aps.org/abstract/PRL/v93/i4/e043901). Therefore, there is room for something like neutrinos to travel slightly faster than light. BruceThomson (talk) 11:58, 24 September 2011 (UTC)

Speed?

In the Speed section there is a value citated for "(1 − (5.1 ± 2.9)×10−5) times the speed of light". In the History section above there is a link to SN 1987A, where it is said that the distance to the object was 168 000 light years. A simple arithmetic shows that this will cause more than 8 years delay of the neutrino, but the burst were received (according to the predictions, etc.) several hours before the light. Aren't there most recent results in the velocity estimation? Or, if the speed significantly depends of the mass and therefore 5.1x10-5 for 3 GeV is not relevant to the observed neutrinos, there should be a bit more qualification text added the for the scope of the applicability of the given speed value.--Dobrichev (talk) 03:04, 15 October 2008 (UTC)

If you assume that the cited central value is precisely correct, then yes, the neutrinos should be delayed by years. The KamiokaNDE II detector was designed for neutrinos of ~tens of MeV, so they should if anything be slower than 3 GeV neutrinos. The problem is that the measured speed has a large uncertainty. It's within two standard deviations of 1. The only thing you can really conclude is that neutrinos travel at a speed that's not too different from the speed of light. If someone manages to do a measurement with smaller uncertainties, then the results from SN 1987a and from terrestrial experiments should be consistent with each other. --Amble (talk) 01:56, 11 November 2008 (UTC)

I don't think there were any Tau Neutrino telescopes aimed at SN 1987A, so perhaps the speed of Tau Neutrinos is a matter of contention. Could it be different flavors of neutrinos travel at different velocities? — Preceding unsigned comment added by 86.179.25.209 (talk) 00:53, 23 September 2011 (UTC)

The comment about energy of the 1987 neutrino burst is wrong - higher energy neutrinos travel slower. 87.119.183.129 (talk) 23:44, 24 September 2011 (UTC)

Does anybody take into account that the observed burst could be focused by the gravitational waves from the same source? Dobrichev (talk) 07:38, 30 September 2011 (UTC)

"like a bullet passing through a bank of fog"

I propose removing this quote, as it's almost spectacularly wrong. A bullet moving through a bank of fog hits every particle of air or water in its path. It leaves wake, often a shock wave that announces its passage to anything with ears within hundreds of meters. It may even whistle, although spin is entirely beside the point here. Contrast this with a neutrino, which can pass through vast quantities of dense matter without affecting anything until it hits a single nucleus in just the right spot, phase, and angle to affect it. And then, maybe, if you have your entire target apparatus wallpapered with photon detectors, you'll observe some of the products of that reaction.
72.208.145.184 (talk) 15:27, 23 September 2011 (UTC)

I agreed, so removed it Seleucus (talk) 15:38, 23 September 2011 (UTC)

The point that I think you're missing is that this is a metaphor, not a literal description of an identical phenomenon. The metaphor was used to describe how neutrinos pass through most matter unimpeded and does so in a very simple way that's accessible to the layperson. Metaphors are meant to be taken loosely and I don't think this one is unreasonable at all. The Cap'n (talk) 16:29, 23 September 2011 (UTC)

I don't think that the passage needs a metaphor adding to aid understanding, the concet of the neutrino passing through matter almost unaffected is easy enough to understand as it is, and adding the metaphor may only add confusion in this case. Koska One (talk) 18:36, 23 September 2011 (UTC)

As a Neutrino passes through matter unaffected, but fundamentally affects the matter it passes through, the metaphor does not really hold. But it was a nice metaphor. Shame to see it go. 2.13.243.160 (talk) 20:42, 23 September 2011 (UTC)

I still see it in the article. Personally, I don't mind it, but note that it is a quote. Wikipedia's not saying it, we're just quoting someone else who did. — Frεcklεfσσt | Talk 13:28, 29 September 2011 (UTC)

EXPERT OVERHAUL DESPERATELY NEEDED!

Expert overhaul of this really quite poorly written article is desperately needed.

The neutrino will for several months if not years be the focus of one of the highest-stakes scientific investingations of all time. It follows that Wiki's article on the topic should be rigorously accurate, coherent and up to date, and copiously detailed. Such standards cannot be met by the usual edit crowd of nattering amateurs.

Let us try to obtain the services of both experimental and theoretical professional working physicists, and give them editing freedom and protection to provide for site needs. --NCDane (talk) 10:50, 27 September 2011 (UTC)

I have a PhD in Particle Physics. I don't have the time to re-write the article but I don't mind proof-reading what other editors write. Dauto (talk) 14:21, 29 September 2011 (UTC)

Flavor vs. Flavour

Could we please have some consistency in the o vs ou? Wikipedia being US-based, I would personally vote for flavor in favor of flavour. zipz0p 18:13, 2 September 2007 (UTC)

That's not how the policy works. The rule is to be consistent with how the article started, or appropriate to the topic (Articles about Queen Elizabeth II use British).81.174.226.229 07:46, 16 October 2007 (UTC)

Fair enough - I really was looking for consistency, which seems to be in place now! Thanks to the editors. zipz0p (talk) 14:30, 19 August 2011 (UTC)

I think that's a Wikipedia record for the latest response ever... Anyways, how does that even make sense? The US spelling is flavor. --WikiDonn (talk) 06:24, 5 October 2011 (UTC)

Speed of Neutrinos

"In September 2011 the OPERA collaboration released data suggesting with 6-sigma significance that neutrinos can travel faster than the speed of light.[30][31] This result has not been detected by previous experiments."

Think that someone should lock this article or parts of the article pertaining to the speed of neutrinos. It's clearly stated in the "Measurement of the neutrino velocity with the OPERA detector in the CNGS beam"

"Despite the large significance of the measurement reported here and the stability of the analysis the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results."

See http://static.arxiv.org/pdf/1109.4897.pdf

Ddanndt (talk) 16:11, 23 September 2011 (UTC)

I read the same paper (being a physics student who's worked at CERN before), but that is what their results suggest (even if they have specifically stated not to read too much into their results), and I think it deserves a mention at least.) Seleucus (talk) 17:01, 23 September 2011 (UTC)

Looks like an anomaly that deserves its own article. --Camilo Sanchez (talk) 17:35, 23 September 2011 (UTC)

It's own article? Oh, yes. Absolutely. You will find that, in a few years time, it will very much need such. Not to mention the ensuing re-write in one or two very closely connected theories. 2.13.243.160 (talk) 20:48, 23 September 2011 (UTC)

Hahaha, indeed. The 2007 Minos paper reports that with a "99% confidence limit on the speed of the neutrino is −2.4 × 10−5 < (v − c)/c < 12.6 × 10−5" and mentions that "theories have been proposed to allow some or all neutrinos to travel along “shortcuts” off the brane through large extra dimensions, and thus have apparent velocities different than the speed of light." That neutrinos, being massive, have velocities different than the speed of light is obvious anyways, In that "different", with hindsight, I sense a whiff of nervousness. 82.56.19.61 (talk) 13:21, 24 September 2011 (UTC)

Yeah okay they can mention it but in a more objective and neutral way like: "In September 2011 measurement of the neutrino velocities with the OPERA detector in the CNGS beam, revealed anomalous supra-speed of light values, which still need to be investigated and confirmed by other independent experiments". Ddanndt (talk) 19:29, 23 September 2011 (UTC)

There are about 65 billion neutrinos passing through each square centimeter of Planet Earth every second, sent by the Sun. How can they tell what neutrino reached the target, with all this background noise? And electromagnetism strongly interacts with matter (causing a refraction and a slowdown in speed) while neutrinos almost don't, they pass through it undisturbed maintaining the same speed all the time. Gravitoweak (talk) 20:45, 23 September 2011 (UTC)

There's no need to say "supra-speed of light values", when you can say "faster than the speed of light". The latter is much clearer.VR _talk 02:17, 24 September 2011 (UTC)

I have seen a lot of interest about this matter, both on the internet (blogs, etc.) and heard about it from people. I came to this article to find verified, reliably sourced information. Thanks for including it. (For what it's worth, I suspect that this is likely to turn out to be an error in measurement.) Axl ¤ [Talk] 09:30, 24 September 2011 (UTC)

Back in 1987 a burst of neutrinos was observed from the supernova SN 1987A about 3 hours before the visible flash was seen. If the photons and neutrinos were emitted at the same time (seems reasonable, but what do I know) the excess speed is about 3 in 4,000,000. Is that comparable to the present observation? SemperBlotto (talk) 14:04, 24 September 2011 (UTC)

Maybe. The current Wikipedia article states that "neutrinos from the supernova had orders of magnitude less energy than the neutrinos observed in the OPERA experiment, as the authors point out." Discussing previous experiments the 2007 MINOS paper, which I referenced above, affirms that "in principle, neutrino velocity could be a strong function of energy." Indeed if, and it's obviously a big if, neutrinos are tachyons, then their energy decreases with increasing velocity. 82.56.19.61 (talk) 16:51, 24 September 2011 (UTC)

From the limits on neutrino masses from the beta spectrum of tritium of about 2 eV (and the comparatively small differences between the individual neutrino masses seen in neutrino oscillation) and the energy of the neutrinos (17 GeV on average), the speed ought to be only about (1 + 7*10^-21)*c, so assuming ordinary tachyons, the measured "excess" speed is wrong by more than 15 orders of magnitude! Icek (talk) 22:26, 24 September 2011 (UTC)

Whatever. Assuming neutrinos are tachyons the difference in neutrino energy necessary to account for the different velocities in the SN 1987A and OPERA measurements is a resonable two orders of magnitude (E_2/E_1)^2≈4.5x10^8/4x10^4, one order of magnitude off the neutrino energy ratio reported in the OPERA paper (around 10 MeV for SN 1987A and 17 GeV for OPERA). As for "the limits on neutrino masses from the beta spectrum of tritium", they are based on neutrinos being bradyons, having real mass. 82.54.83.42 (talk) 06:52, 25 September 2011 (UTC)

The (imaginary) masses would have to be much larger than the limits for the masses - and these limits are still valid if energy is conserved. The energy of the tachyonic neutrino of mass i*m is still i*m/sqrt(1 - v^2/c^2) = m/sqrt(v^2/c^2 - 1). Icek (talk) 11:08, 25 September 2011 (UTC)

The limits are derived under the assumption that the real mass is sandwiched between that corresponding to the supposedely subluminal speed and 0 correspomding to c. 95.246.56.38 (talk) 12:54, 25 September 2011 (UTC)

No, "that", i.e. the speed is what is derived, it is not an assumption. The assumption is only the relativistic relation between mass, speed and energy which I mentioned above. The point is that with the tachyonic assumption you get the same mass limit. Icek (talk) 10:21, 26 September 2011 (UTC)

Regarding the discussion of the 2007 MINOS experiment, the article says: "While the central value is higher than the speed of light, the uncertainty is great enough that it is very likely that the true velocity is not greater than the speed of light". My understanding is that the MINOS estimate for the neutrino speed was greater than the speed of light by about 1.8 sigma, which is apparently low by particle physics standards, but even so, this suggests that their result is consistent with superluminal speed at ~96% confidence level; accordingly, I think the aforementioned sentence should avoid saying that the experiment found that it is "very likely" that the speed was not superluminal. Also, regarding this and the more recent OPERA speed result, I had a more theoretical question for the sake of my own curiosity (I haven't seen this discussed elsewhere and I figured this was as good a place as anywhere to post it): do any special approaches or "corrections" need to be used by the researchers to use an inertial frame of reference for these experiments, so that special relativity is applicable?--GregRM (talk) 15:14, 25 September 2011 (UTC)

I'm very excited about these results just like everyone else, but I don't think anything should be written about the phenomenon until it is conclusive. The results could very well be due to experimental error, in which case we have something in this article that will probably have to be removed. — Preceding unsigned comment added by 174.109.94.64 (talk) 17:01, 26 September 2011 (UTC)

I think that we should include the latest data, with a message that it could be due to experimental error, if as I expect it is wrong we can always change it. That is a big plus to an online encyclopaedia 8digits (talk) 10:49, 13 November 2011 (UTC)

No, they really didn't go faster than light

Turns out the problem was incorrect use of data from a GPS satellite, which hadn't been corrected for certain relativistic effects that only arise in an experiment on objects traveling near the speed of light. In short, however, relativity has been confirmed, since the neutrinos didn't have to travel quite as far as the experimenters thought they did. The final story is most interesting. [2] SBHarris 01:50, 16 November 2011 (UTC)

The preprint that article cites has been (extensively) debated at Talk:OPERA neutrino anomaly—there's an entire archive dedicated to it. In particular see this article, which was cited in OPERA neutrino anomaly before the entire section mentioning van Elburg's preprint was removed. 74.74.150.139 (talk) 02:35, 16 November 2011 (UTC)

Ah, I see it. They cleverly put it at the FRONT of the talk page (not the end) and hid most of it in an archive. Sheesh. For anybody interested, the link to the archive is above, and the paper preprint is here: [3]. Apparently OPERA has answered this guy's objections, so that's that. SBHarris 02:49, 16 November 2011 (UTC)

Tom Roberts is a physics professor, often on the usenet and his comments are when questioned on this article

http://www.spacebanter.com/showthread.php?t=177681

The author obviously does not understand how the GPS actually works. The satellites are NOT moving "West to East in a plane inclined at 55 degrees to the equator" -- SOME of them may well do so, but there are three different orbits, and two others are at quite different inclinations. Moreover, the clocks are all synchronized in the ECI frame the GPS uses, which is not rotating, and in which the center of the earth is at rest. That is, each satellite's clock displays the coordinate time of the ECI frame at its current location -- all effects due to the satellites' altitude and motion relative to the ECI are fully accounted for.

Moreover, the presence of the atomic clocks at the two locations are used to reduce systematic errors, but they are synchronized via the GPS, so it is the GPS synchronization that matters. That is known to be accurate to 2-3 ns (with a suitable integration time, which they have).

The OPERA result of superluminal neutrinos will be extremely interesting, IF IT HOLDS UP. At present, many/most physics do not believe it will hold up. But then, I have not seen any plausible description of an error....

Tom Roberts 8digits (talk) 12:37, 18 November 2011 (UTC)

SN 1987A neutrinos did not arrive several years before the photons??

Had neutrinos from SN 1987A traveled faster than light by this factor, they would have arrived at Earth several years before the photons; this was not observed to be the case.[nb 6][32]

In this sentence I read that researchers studied neutrino events in the "several" years before SN 1987A and did not find them until 3 hours before the visual detection of the event. The reference doesn't say this and I don't believe this is true. I would welcome information about a continuous neutrino study in the years 1980-1987. — Preceding unsigned comment added by 83.160.57.73 (User talk:ThorAvaTahr) 07:16, 26 September 2011 (UTC)

• What matters is that contradictory events were observed. Neutrino detections of the kind expected happened exactly at the time expected. If the neutrinos had passed through the planet years before then they wouldn't have been there. — Preceding unsigned comment added by 167.206.48.220 (talk) 23:27, 26 September 2011 (UTC)

But maybe not all neutrinos travel faster than light. If some do, under certain circumstances, there may have been a small pre-echo of the SN 1987A. Was there an experiment running at the time that could detect this? — Preceding unsigned comment added by 50.92.215.62 (talk) 19:24, 21 November 2011 (UTC)

Edit to be Scientifically Accurate

I propose that this article as it concerns the big bang should be edited by the administrators to reflect the fact that the big bang is merely a theory and has not been conclusively proven. The wiki-page for the big bang is properly worded to emphasize this; this page, however, is not. — Preceding unsigned comment added by 216.227.39.113 (talk) 00:34, 10 October 2011 (UTC)

See these pages for the meanings of "theory" and "proven" in science. Adrian J. Hunter^{(talk•contribs)} 02:36, 17 October 2011 (UTC)

Any use for pop science video links probably not accessible from most countries?

Much as I like the BBC's science programming, I don't think a poetic description of the neutrino's behaviour and an iplayer link belonged in the intro. Wikipedia is about facts. Here is the snipped text.

, "like a bullet passing through a bank of fog". http://www.bbc.co.uk/iplayer/episode/b0106tjc/In_Our_Time_The_Neutrino/ Frank Close speaking on the BBC programme In Our Time, April 2011]

86.24.87.222 (talk) 00:57, 17 October 2011 (UTC)

"refute" the theory of relativity?

(Note: I am not a physicist, nor do I want to be.) The claim that faster-than-light neutrinos would "refute" the theory of relativity seems a little too strong of wording to me. E.g., special relativity does not "refute" Newtonian mechanics; it generally agrees with Newton's laws for most applications (but with a small error). Were the recent faster-than-light observations to hold up to further scrutiny we wouldn't say that relativity has been "refuted", but we simply have more clarity and (hopefully soon) a more accurate model for our universe. (Please correct any erroneaous claims I've made here.) Thanks, 74.139.12.245 (talk) 01:11, 20 November 2011 (UTC)

I read that it would disprove very fundamental principles of the theory of relativity - minor changes would probably not be enough to make this theory compatible with fast neutrinos.

I understand what you mean when you say that "special relativity does not refute Newtonian mechanics", but I thinks that in a (good) sense it refutes it.

What better formulation in the article would you suggest to convey the tremendous impact of fast neutrinos to current understanding of physics?--Pavel Jelinek (talk) 19:04, 20 November 2011 (UTC)

Measurement of neutrino types

The section on oscillation mentions "detecting" a neutrino's type. Nowhere in this article could I find any distinguishing properties of the three types except mass, which has never been observed. So if neutrinos can be told apart, how? and what confirmed difference does that reflect? — Preceding unsigned comment added by 208.60.35.95 (talk) 15:27, 3 July 2012 (UTC)

The different types of neutrino flavours, can be told apart, by the charged lepton that they produce, when they interact via the weak-nucear force. Note that the different neutrino flavours eigenstates states are not the same as the mass eigenstates. This shows that they have Lepton number although neutrino oscillation breaks this conservation law.Dja1979 (talk) 19:58, 4 July 2012 (UTC)

Stability?

Are neutrinos stable particles or do they decay? Or is this unknown? -- 92.226.26.35 (talk) 01:47, 25 July 2012 (UTC)

This isn't the appropriate forum for such a question. ("Talk" pages are intended for discussions about how to improve the corresponding articles.) Perhaps you should try a site like Physics Stack Exchange. Justin W Smith (talk) 02:11, 25 July 2012 (UTC)

Neutrino Density and Human Harm

I am not SME on this subject, so I can only observe and seek additional clarification from someone who has the knowledge.

In the first section of the article, the statement is made "About 65 billion solar neutrinos per second pass through every square centimeter perpendicular to the direction of the Sun in the region of the Earth."

Although a big number, I have no problem. I read a recent text that discussed neutrino densities (citation: The Beginning of Infinity = Explanations that Transform the World, 2010, Penguin Books, © David Deutsch) that said [In the vicinity of an exploding supernova,] "... neutrino radiation alone would kill a human at a range of billions of kilometres, even if that entire distance were filled with lead shielding."

At what densities would harm to humans become a problem? Does mankind currently have capabilities of producing such densities? Bcwilmot (talk) 00:45, 20 May 2012 (UTC)

A way to calculate this is to establish the amount of absorption in a human corresponding to a lethal radiation dose. Graeme Bartlett (talk) 11:33, 7 October 2012 (UTC)

Being affected by matter

At the moment there seems to be some editing in the introducting along the lines "They are therefore able to travel great distances through matter neither affecting the matter nor being affected by it". However neutrinos travelling through matter are affected via the MSW effect. So this seems to be an untrue statement. It is more true to say hey are therefore able to travel great distances through matter without affecting the matter. However I can see why people would argue for the current wording so before changing it I would like some other opions.Dja1979 (talk) 21:26, 6 October 2012 (UTC)

Thanks for pointing this out. The article’s verbiage is clearly wrong as it stands. I would opt for “unimpeded” in place of “neither affecting the matter nor being affected by it”. I assume the original intent was to convey that neutrinos typically survive vast distances through dense matter. Strebe (talk) 23:07, 6 October 2012 (UTC)

I think unimpeded is better, but still not quite right. As the MSW effect is to make neutrinos in matter have a different effecitive mass. So my interpretation is, that they are being impeded. Dja1979 (talk) 01:43, 7 October 2012 (UTC)

Please explain how that amounts to “impeded”. Strebe (talk) 07:45, 7 October 2012 (UTC)

I suppose it's whether you consider the mass state or the weak state the neutrino. The MSW effect means that most of the neutrinos are in the higher mass state. The electron neutrino is made up by (ν_e = ν₁ cosθ + ν₂ sinθ), so as there are less ν₁ less ν_e are detected, so the ν_e state has been impeded.Dja1979 (talk) 12:53, 8 October 2012 (UTC)

Since neutrinos only interact through the weak force and gravity, their mutual interaction with matter is very weak, but it's not zero. So it is indeed wrong to say that they can travel through matter without being affected, but it is equally wrong to say that the matter is not affected, as shown by the existence of neutrino detectors. I guess the sentence was meant like "The mean free path of a neutrino in matter is very long / a great distance." It's a bit a matter of taste if one calls them "affected" as soon as their effective mass changes, or only in the moment their wave function collapses in one or the other weak eigenstate. The latter can indeed be described by a mean free path that is large, but not infinite. I would suggest "They are therefore able to travel great distances through matter with a very small chance of interacting with it." — HHHIPPO 11:57, 7 October 2012 (UTC)

I think this gets away from any ambiguity.Dja1979 (talk) 12:53, 8 October 2012 (UTC)

I think it does not. The objection User:Hhhippo makes applies to his own suggestion. There is no difference between “interacting with” and “affecting and being affected by”. By the MSW effect, the “interaction” is essentially constant, not “a very small chance”.

I also don’t agree with User:Dja1979’s objection to “impeded”. The question isn’t whether some particular state is attenuated (or enhanced, for that matter); it’s whether “the neutrino” traverses dense matter for great distances with little change in velocity (implying little change in energy and direction). One might argue whether it’s the “same” neutrino if it oscillates or changes mass, but that’s largely a metaphysical question not terribly relevant to what the sentence is trying to say. I’m not wedded to “impeded”, but it sure seems like the right word. I’d be happy if someone came up with a better one, but I wouldn’t be particularly happy if the sentence became long, unwieldy, and pedantic because then it would lose its raison d’être. Strebe (talk) 03:05, 9 October 2012 (UTC)

Indeed my above suggestion doesn't fully solve the problem. Even without going into the details of oscillations and related effects, gravitation alone is a mutual interaction between neutrinos and other matter, and it doesn't have any 'free path'. So I would suggest instead "They are therefore able to travel great distances through matter, interacting very little with it." This implies (a) they can travel great distances at all, without being stopped or destroyed, (b) they have little influence on the matter, (c) the matter has little influence on them. "Little" is of course not a quantitatively well-defined description, and neither is "great distances", but as you said, this is not supposed to be a full treatment, just a sentence in the lead, concise but not wrong. — HHHIPPO 22:38, 9 October 2012 (UTC)

Impede is better than what's there so I won't object to that being used. My main objection to the original was "They are therefore able to travel great distances through matter neither affecting the matter nor being affected by it" when in the MSW efect they travel great distances but are affected by the matter (although they still neutrinos so this is different to being detected in neutrino detectors). So maybe the suggestion by User:Hhhippo isn't the answer. As I said I don't have the right words, and either is better than what's there.Dja1979 (talk) 16:16, 10 October 2012 (UTC)

I opted for “Therefore a typical neutrino passes through normal matter unimpeded.” It’s as short as I can make it and still be correct. “Typical” conveys there is a finite probability it won’t make it. “Normal matter” disqualifies neutronium, for example. The article body goes into detail about just how neutrinos affect and are affected by matter, so I don’t see any need to qualify the sentence further. Strebe (talk) 05:29, 11 October 2012 (UTC)

Fine with me. — HHHIPPO 07:18, 11 October 2012 (UTC)

Origin of mass

The article contains this sentence:

"If, like other fundamental Standard Model particles, mass is generated by the Dirac mechanism, then the framework would require a SU(2) singlet."

The phrase "Dirac mechanism" is not clear (is it established terminology?), and links to an article called Dirac Mass, which has since been redirected to Dirac Equation, which does not explain it at all, in my opinion. Is it possible that this should be "Higgs mechanism" instead? Elroch (talk) 09:52, 5 November 2012 (UTC)

No, because both the Majorana mechanism and Dirac mechanism allow for coupling to the Higgs field.Dja1979 (talk) 19:50, 5 November 2012 (UTC)

I understand that, but it's a matter of the terminology. The phrase "Dirac mechanism" seems little used, and it would be good if a reader was directed to somewhere that explained it. The link is currently unhelpful, possibly because an old article has been redirected. Elroch (talk) 00:45, 6 November 2012 (UTC)

Would this link be better Dirac fermion? Maybe someone needs to expand the Dirac fermion page. Finding whether neutrinos are a Dirac particle, like all other fermions in the Standard Model, or Majorana is an intense area of research at the moment with at least 10 separate, current or planned, experiments to investigate whether it is Majorana. As I said before the both allow for the Higgs, so cannot be replaced by that.Dja1979 (talk) 03:31, 6 November 2012 (UTC)

Limit of neutrino mass according to EXO-200.

This article says "The lowest limit, on the Majorana mass of the neutrino, has been set by EXO-200 140–380 meV", but the article on EXO-200 says "which relates to an upper limit on the neutrino mass of 140–380 meV" (my underscores). --Episcophagus (talk) 18:10, 8 November 2012 (UTC)

EXO-200 has realest an upper limit on the neutrino mass, which is lower than any other upper limit, hence the lowest limit. So both statements are correct aren't they? At the moment there is no limit on the lower limit of the (lowest mass neutrino) neutrino mass, it can be 0 (as long as the other 2 have mass).Dja1979 (talk) 19:31, 8 November 2012 (UTC)

You mean that "lowest limit" should be read as "the lowest upper limit"? If so, it ought to say so in the text, because the writing as it stands is confusing - at least to me! --Episcophagus (talk) 21:33, 8 November 2012 (UTC)

You are right, it isn't explicitly said, and to keep it in the same style as the rest of the article it should be changed, which I have now done. My personal opinion is that the lowest lower limit isn't very noteworthy as that would imply there are better limits.Dja1979 (talk) 22:32, 8 November 2012 (UTC)

photons made from neutrinos?!

I see a mention of "neutrino theory of light" mentioned in the section on anti-neutrinos. Is that for real? I mean, is that a crackpot idea, an old dropped idea, serious work beyond the standard model, or what? I see that it links to an article, but I think this sentence needs qualifications with where it comes from since it is not part of the Standard Model, as is generally the implication of facts stated in this article without weasel words. —Długosz (talk) 00:58, 9 November 2012 (UTC)

I agree. Do we want to drop it altogether? As it has basically been disproven by neutrino oscillation, hence neutrino's having mass. Dja1979 (talk) 01:33, 9 November 2012 (UTC)

See the 1930's Pascual Jordan theory of light being composed of neutrios, page 419 in Abraham Pais _Inward Bound_. Pais even did both and English and German ditties to the tune of Mack the Knife:

Mister Jordan

Takes neutrinos

And from those he

Builds the light.

And in pairs they

Always travel

One neutrino's

Out of sight.

Pais mentions that the Jordon's theory was shown to be mathematically unworkable, long before neutrinos were detected, much less before they were found to have rest mass. I don't know what was wrong with it, however. SBHarris 01:47, 9 November 2012 (UTC)

So it's clear, that under no current understanding of particle physics are photons considered composite particles. So this statment should reflect that, if it's there at all. Dja1979 (talk) 13:45, 9 November 2012 (UTC)

Absolutely. These are old tentative ideas, long disproven. SBHarris 05:05, 10 November 2012 (UTC)

So it should be removed? Otherwise we could fill a whole page of theories that have been proved wrong. Dja1979 (talk) 03:35, 11 November 2012 (UTC)

Size section

This question and possible suggestion for the "Size" section is based on National Geographic article (and a few others) out there; my knowledge of physics is extremely limited. But at http://news.nationalgeographic.com/news/2009/06/090602-particles-larger-than-galaxies.html they describe a 2009 paper

According to quantum mechanics, the "size" of a particle such as a neutrino is defined by a fuzzy range of possible locations. We can only detect these particles when they interact with something such as an atom, which collapses that range into a single point in space and time.

For neutrinos created recently, the ranges they can exist in are very, very small.

But over the roughly 13.7-billion-year lifetime of the cosmos, "relic" neutrinos have been stretched out by the expansion of the universe, enlarging the range in which each neutrino can exist."We're talking maybe up to roughly ten billion light-years" for each neutrino, said study co-author George Fuller of the University of California, San Diego."That's nearly on the order of the size of the observable universe."

Such large ranges can remain intact, the scientists suggest in the May 22 issue of Physical Review Letters, since neutrinos pass right through most of the universe's matter.

The current entry just gives numbers around 10^(-33) meters, and the current text here on wikipedia does say "Average" (in accordance with the "fuzzy range" mentioned in the quote) but our entry does not tell the reader that this range can be "stretched" over time. Two things maybe worth adding to our entry then? First, even if the 2009 paper is wrong about "by now ...10 billion light years" it seems still mentioning that the range can increase over time to much larger numbers. If in addition the "10B LY" estimate is accepted by physicists then this too (not just that the range increases over time to something much larger since they neutrinos can go a long long distance/time without interacting) See also http://physics.aps.org/story/v23/st17 for a somewhat more technical summary than the National Geo. ref given above. Hopefully more expert editors can confirm/deny/comment and help draft the wording of what to add re "size" here.. (been said before and will be said again, by others and me: strange and fascinating universe...) Harel (talk) 02:55, 3 May 2013 (UTC)

Discovery of the Higgs

The sentance that says "making it the latest particle of the Standard Model to have been directly observed". The particle that's been discovered at the LHC has been confirmed to be the Higgs. Okay they haven't said which one, but at the moment nothing says that it's not the Standard Model Higgs. But in anycase, no matter which one it is, I don't think really matters which one it is as the tau neutrino is not the one predicted by the vanilla Standard Model, as it has mass. Also the Higgs Boson page also says it has been confirmed so to be self consident the two pages should agree.Dja1979 (talk) 17:08, 9 May 2013 (UTC)

Recent edits

Neutrinos do not carry electric charge, and thus cannot be captured or deflected by electric or magnetic fields. Neutrinos are affected only by the weak interaction (which is of very short range, meaning that interaction seldom occurs), and by gravity (which has a negligible effect on a particle carrying so little mass). As a result, most neutrinos sail through normal matter without any significant interaction, continuing on their paths just as though the matter were not there.

This description contains parenthetical asides, which are generally considered inappropriate for encyclopædic text. “Sails through” is not literally correct and could confuse readers of English who are not native speakers. The final sentence says the same thing twice.

Most neutrinos found in our vicinity emanate from the Sun. Every second, a huge number of these solar neutrinos (about 65 billion (65×10⁹)) pass through every square centimeter of nearby space.

Another parenthetical statement, and, comparing to the original:

Most neutrinos passing through the Earth emanate from the Sun. About 65 billion (6.5×10¹⁰) solar neutrinos per second pass through every square centimeter perpendicular to the direction of the Sun in the region of the Earth.

Eliminating perpendicular to the direction of the sun loses important information: That the great quantity passes through a plane normal to a ray from the sun is how we know they are from the sun and not just from all directions.

Thanks. Strebe (talk) 22:46, 11 May 2013 (UTC)

I agree with the points that Strebe has made.Dja1979 (talk) 22:54, 11 May 2013 (UTC)

Interaction

"the neutrino does not interact electromagnetically", but it has spin, so it should react with electromagnetically. Jackzhp (talk) 18:55, 13 October 2013 (UTC)

the neutrino does not interact with the gauge boson (photon) that carries the electromagnetic force. Spin is a property of particles but have nothing to do with whether it inteacts with the photon or not.Dja1979 (talk) 20:25, 13 October 2013 (UTC)

Removed incorrect section

I removed the section "Alteration of nuclear decay rate" because that hypothesis has been disproven. You can read about it here: http://wattsupwiththat.com/2010/09/27/more-follow-up-on-the-solar-neutrinos-radioactive-decay-story-experimental-falsification/

Foobaz·o< 07:48, 19 November 2013 (UTC)

Notes

Note 7 needs to be cleaned up. What is called 'actual' heat is referring to 'waste' heat, the heat that must be dissipated external to the plant. The roughly 33% of the thermal power that ends up as electricity begins as heat in the core too and is used to make steam for the generators. Recommended fix is change "4,000 MW reactor would produce only 2,700 MW of actual heat" to "4,000 MW reactor would produce only 2,700 MW of external waste heat" — Preceding unsigned comment added by 24.61.212.124 (talk) 07:18, 18 December 2013 (UTC)

Mass Units

Would someone with a physics background mind converting all the predicted values in the Mass section from eV to eV/c^2 or some other SI unit of mass? The masses for all the other particles in wikipedia are given in eV/c^2 or g and I would like to be able to compare the mass of the neutrino to those, but a layman reader like myself doesn't know to apply the mass-energy equivalency principle, especially to particles that are traveling at relativistic speeds. — Preceding unsigned comment added by 67.41.1.220 (talk) 18:40, 5 December 2013 (UTC)

• When used for mass, eV and eV/c^2 mean the same thing. Technically, eV measures energy, while eV/c^2 is mass. But particle physicists often abbreviate eV/c^2 to just eV, because they think of mass as one specific type of energy. A lot of their work involves energy turning into mass and vice versa so they don't need a hard distinction between the two. A description like "10 eV of mass" means "10 eV of energy, currently in the form of 10 eV/c^2 of mass". Foobaz·o< 03:48, 13 December 2013 (UTC)

Regarding the neutrino having some small mass: The light burst and the neutrino burst from the 1987A nova arrived at Earth at essentially the same time. The SLIGHT difference in arrival times is connected to theories regarding nova dynamics (the neutrino burst is SLIGHTLY behing the immediate photon burst. THUS: Since the Magenellic Cloud from which 1987A was observed is about 250,000 light years from Earth the near simultaneous arrival of neutrino and photon bursts strongly suggests that like photons the neutrino must have no mass.

It is possible this is an old article but I strongly suggest you ask someone higher on the respect tree than myself regarding the mass issue of this article. Charles Thompson Instructor Physics, Astronomy MS Physics Clemson University. — Preceding unsigned comment added by 199.67.16.60 (talk) 18:04, 27 January 2014 (UTC)

According to SN 1987A#Neutrino emissions, the neutrino burst preceded the light arrival by several hours. (This predictably stoked faster-than-light theories and also lent credence to OPERA’s faster than light neutrino detection.) Hence I wonder where your information comes from. Strebe (talk) 05:59, 28 January 2014 (UTC)

Physics articles with 30+ authors

Citation bot recently[4] expanded some of the citations to include all 30 co-authors of some of the papers. I'm not sure if this is a good idea or not and I've started a discussion at User talk:Citation bot/Archive1#Physics articles with 30+ authors.--Salix alba (talk): 20:34, 24 March 2014 (UTC)

How are they actually made?

Unless I have missed something, this article does not explain how neutrinos are made. It lists some sources of neutrinos, and it explains how antineutrinos are made ("...these are emitted during beta particle emissions, when a neutron turns into a proton"), but not neutrinos. Do protons turn into neutrons? Can someone who knows more about this add a section on this? Richard75 (talk) 23:14, 29 May 2014 (UTC)

In the introduction there is "Neutrinos are created as a result of certain types of radioactive decay, or nuclear reactions such as those that take place in the Sun, in nuclear reactors, or when cosmic rays hit atoms. There are three types, or "flavors", of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos. Each type is associated with an antiparticle, called an "antineutrino", which also has neutral electric charge and half-integer spin. Whether or not the neutrino and its corresponding antineutrino are identical particles has not yet been resolved, even though the antineutrino has an opposite chirality to the neutrino." Does this not satisfy your point? To answer you question "Do protons turn into neutrons" the answer is yes. It depends on the nuclei. Beta decay#Nuclear transmutation probable explains it better than I can here.Dja1979 (talk) 00:14, 30 May 2014 (UTC)

The paragraph you quoted does not say how they are made, apart from saying it's "types of radioactive decay," which is too vague. It should not be necessary to refer to another article to find out: it should be here. Richard75 (talk) 10:56, 1 June 2014 (UTC)

65 billion neutrinos

How is "6.5×10¹⁰" an improvement on "65 billion"? It's gobbledygook to many people. Richard75 (talk) 10:53, 1 June 2014 (UTC)

PS:- There is nothing in Wikipedia:Manual of Style/Dates and numbers#Numbers to say there is anything wrong with saying 85 billion. Richard75 (talk) 18:01, 1 June 2014 (UTC)

Hello Richard75. I reverted your change. The definition of billion has some ambiguity in English-speaking countries. Outside of the US, amongst some older people “billion” means “million million” rather than “thousand million”. Anyway, later in the article it says, “65 billion (6.5×10¹⁰)”, and I think that’s the best solution. Strebe (talk) 23:17, 1 June 2014 (UTC)

Thanks. I've done it that way in the first place it appears too. Richard75 (talk) 14:17, 2 June 2014 (UTC)

Do we need to change article details about electromagnetic force?

The neutrino has spin, so it does respond magnetically to electromagnetic fields. There are some places in the article and sidebars that say it does not.

Those should be changed to say it does not respond to electric fields.67.101.139.55 (talk) 19:07, 13 November 2014 (UTC)Fred Bortz

I don't see how "spin" proves a response to electromagnetic fields. Spin causes "magnetism" only of a particle has intrinsic change, which neutrinos do not (neutrons have an internal charge distribution that takes care of this). There is no charge or dipole moment in a neutrino. I have no reason to think neutrinos respond to electric fields in any way. SBHarris 21:55, 13 November 2014 (UTC)

A neutrino has a non-zero (but really small) magnetic moment because: 1. Neutrinos have non-zero masses and three types of charged leptons (electron, muon, tauon) have different masses. 2. Neutrino spin is non-zero. On 1-loop level, a photon couples with a neutrino indirectly through a W boson or a charged lepton.2401:DE00:1:6:DC7E:4730:4652:B136 (talk) 01:29, 19 November 2014 (UTC)

Neutrino Size

The 'Size' section contains two seemingly contradictory statements: "Standard-model neutrinos are fundamental point-like particles, so they have zero volume", and "Since the neutrino does not interact electromagnetically, and is defined quantum mechanically by a wavefunction instead of a single point in space, it does not have a size in the same sense as everyday objects."

I would argue for removing the first sentence and replacing it with the second. Phuhem (talk) 09:28, 9 January 2015 (UTC)

Both these statements are problematic. I've trimmed both, but they are still not ideal. —Quondum 15:08, 9 February 2015 (UTC)