Why did 11 nuetrinoes decide to interact with the water in a deep mountain detector during the 1987 super nova event?
I mean, come on! 11 out of trillion and trillions?
Why just 11? What was in it for them?
Neutrinos very very very rarely react with other matter. I’ll leave it to the resident nuclear physicists to explain why. But that is precisely why they make the detectors so dang big in the first place.
Neutrinos are really really small.
Matter is mostly empty space. The vast majority of neutrinos pass right through matter without touching it. Because they have no magnetic charge, we can’t detect the effects of their motion. Occasionally, by pure random chance, a neutrino will crash into some matter, and we can detect that.
Like many other particles, neutrinos are thought to be structureless, point particles (i.e. “really small”), so it’s not that. On the other hand, no known elementary particles have a magnetic charge. Neutrinos are thought to have a zero magnetic moment, but they’re not unique in that respect either and that’s irrelevant to the question at hand.
What makes neutrinos relatively unusual is that they’re (sort of - I’ll ignore oscillations) stable and can only interact via the weak force. By contrast, something like a photon from SN1987a was also stable, but will react with other particles via electromagnetism. And had the explosion spat out any protons that reached us - it did, but they didn’t - they could have interacted both electromagnetically and via the strong force.
As the name suggests, the weak force is, well, weak. So even if a neutrino passes close to an atom in a detector on Earth, an interaction between them is unlikely. Much less likely than for an electron, which can interact electromagnetically, passing as close.
As to why the weak interaction is weak, that’s about how it comes about. For both the electromagnetic and weak interactions are versions of the same underlying force. In a sense, they have exactly the same strength. But physicists understand such forces between particles as coming about by the exchange of other particles. The difference between the weak and electromagnetic forces is that, while they have the same underlying strength, the particles carrying the weak force (the W and Z bosons) have mass and those carrying electromagnetism (photons) do not. And in this context, massless particles can reach further than massive ones. The weak force is thus like electromagnetism, but with a shorter range. Hence interactions via it are less likely.
As to why those particular eleven, all this is quantum mechanical and hence the best one can do is talk about probabilities. One can estimate the (small) probability that any particular neutrino would be detected. Which ones it was going to be, you can’t say.
Incidentally, it’s believed that astronauts can occasionally see the flashes caused by cosmic rays interacting with the fluid in their eyeballs. Someone extended this to SN1987a and pointed out that the total amount of water in human eyeballs is such that someone probably had one of the neutrinos create a flash in their eye that they noticed. But they, no doubt, never realised what it was.
Reaching out into science fiction a little, but suppose we had a detector that could capture and register incoming neutrinos as well as, say, Hubble does with photons. What would we see? It seems to me that due to neutrinos interacting so weakly with matter (until they hit our detector…details of which omitted for clairty 
) we’d be able to “image” objects very distant from us, even with tons of interspersed matter. What would e.g. the Sun look like in “neutrino-vision” ?
Remeber the further you look in distance, the further back in time you see.
Currently we’re only able to see as far back as 300,000 years after the big bang (using the CMBR) as this is when the (photon) de-coupling era began (i.e. the universe became transparent).
The neutrino decoupling era is thought to of began only a few seconds after the universe was formed, so a good ‘neutrino telescope’ should enable us to see right back to the early universe.
The sun is a source of neutrinos.
Also I’m suprised it hasn’t been noted yet but there are three differnet types of neutrinos known to scientitst’s - electron neutrinos, muon neutrinos and tauon neutrinos each with a corresponding antiparticle.
I don’t think you’d get to see much of anything other than the neutrinoes themselves. After all, vision is a phenomenon of percieving particles that react with other particles before coming to your eye. If you see neutrons that have passed through whole galaxies worth of matter without interacting, you wouldn’t end up with much.
But it would be a neat way to look for black holes: You know that anything less than a black hole will only grab up a miniscule percent of neutrinos, so if you see any `holes,’ you’d know that something was in that direction.
legion is your op title a nod to the book “4 Dada Suicides?”
bonzer does a nice job of explain some of the problems with detecting neutrinos, but some other points:
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You can quibble about whether particles are points or not, but they do have wavelength, which affects the chances of being captured by a neutron. The everyday neutrinos we are talking about have wavelengths under 10[sup]-18[/sup] meters, which is “quite a bit” smaller than, say, visible light (under 10[sup]-6[/sup] meters.) Something that is for all practical purposes 12 orders of magnitude smaller is far less likely to hit something.
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Matter consists mainly of electron shells with tiny, but heavy, nuclei. Light can be captured by the electrons. Neutrinos need to be captured by some of the particles in the nucleus. Hence, the targets themselves are smaller.
So the odds are very small in capturing natural neutrinos. (Put a detector near a reactor and you can count neutrinos all you want. But the odds are still the same: there are just more flying by.) Scientists are good with working out how big to make a neutrino detector so they can capture enough that they can write papers and keep their funding. (If they ask for too big of a detector, it won’t be funded.) The Leading Edge is like that.
Solar neutrinos have been observed for a long time. This article describes the Solar Neutrino Problem (and a very probable solution) which has been the center of focus in this field.
Of course the neutrino detectors today do not have any angular resolution (imaging capability). If we could make an imaging neutrino telescope, the sun should look like a very small and fuzzy blob. The neutrinos are produced by the fusion reaction in the sun’s core and escapes without much interaction with the bulk of the sun’s mass, so we’d be getting an unobstructed view of the fusion reaction. This should tell us a lot about the structure of the sun’s core. There may be significant scattering, but if so that would also be interesting to look at.
How cool! A sort of “X-Ray” for the solar system. (I know we can observe X-rays too.) Would neutrinos be a good communication method for an advanced civilization that could capture and transmit them at will, since they pass through almost anything? I guess they’d still have that old “speed of light” problem.
And all this talk about neutrino mass!
So not only do they prove the existence of a deity, but a Roman Catholic God at that?!
Oh.
Never mind.
Perhaps, though you still wind up with a less than c velocity and you still have to capture them to decode the message.
That’s what Bonzer was referring to when he said “I’ll ignore oscillations”.
Ironically, X-ray images of the sun shows the outer layer (corona) while the visible light shows the structure a couple of layers lower (the photosphere). That’s because the corona is too diffuse to emit or absorb visible light but hot enough to emit X-rays.
By the way, we already have one method of looking into the sun. It’s called helioseismology, i.e the studiy of solar oscillations (vibrations). Not only can we measure the density and velocity distribution beneath the surface, but we can even see sunspots on the far side of the sun. We can’t yet see the inner core or the high latitude regions, but it’s still a very impressive and useful tool.
It might be, if we can find a practical way to generate, focus and modulate a neutrino beam and if we find a way to capture (detect) them efficiently. Those are very big IFs.
DarrenS: The Super-Kamiokande group has a picture of the sun using neutrinos:
http://antwrp.gsfc.nasa.gov/apod/ap980605.html. Poor angular resolution (as mentioned by scr4), but very cool nonetheless.
ftg: Regarding the light absoprtion (by an atom) and neutrino scattering analogy you are drawing:
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When a neutrino interacts with, say, a neutron, the neutron does not absorb the neutrino. Indeed, as far as we know, something related to the neutrino must come out after the interaction. (That something will be either a neutrino or a charged lepton (e.g. an electron)). Contrast this with light absorption, where a photon resonantly excites an atom, disappearing from existence in the process.
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Neutrinos need not interact with the nucleus. The electrons are fair game. (Neutrino-electron scattering played an important role in the SNO result described in the article linked to by scr.)
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While it is true that solar neutrinos have a much shorter wavelength than visible light (they’re about 7 orders of magnitude apart), this fact is a red herring when it comes to explaining why they interact so weakly. As bonzer described, the weak interaction is weak, and it’s the only interaction that affects neutrinos.
Neutrinos can indeed serve as interesting probes of the universe. In supernovae, for example, a photon produced in the star’s interior won’t make it to our telescopes straightaway because of all the material in the way. It takes hours for optical photons from a supernova’s interior to reach the outside. Thus, these photons cannot provide detailed information about the early stages of core collapse. Neutrinos, on the other hand, leave the star relatively unimpeded. The arrival times and energies of these neutrinos contain information about the dynamics of the collapse. What’s more, the neutrinos give optical astronomers a few hours head start on aiming their telescopes.
(And because neutrinos get out so easily, 99% or so of a supernova’s energy leaves in the form of neutrinos.)
Off to a neutrino detector (no lie)…
-P
But the other types are not only generated in oscillations, the muon neutrino is generated by the decay of an antimuon or a pion for example.
Wow, I’m embarrassed I didn’t know about this. Do you know if the poor resolution is mostly due to instrumental limitations or actual scattering of neutrinos?
I was thinking about this a little more and opened a new thread on the idea that if neutrinos change mass then the velocity will change. Now if this happens randomly your final signal may get smeared out due to aliasing from the differing arrival rates. Assuming they’re traveling far enough for it to matter of course.
A little more detail: In the neutrino oscillation mentioned earlier, one type of neutrino can change into another (and back again, repeatedly, hence “oscillation”), but they stay neutrinoes. And it’s not quite clear that each has an antiparticle: It’s possible that neutrinos are their own antiparticles. I would recommend not mentioning this to a particle physiscist, though: All particle physicists are absolutely sure about whether neutrinos are their own antiparticle, but unfortunately they don’t all agree.
And while neutrinos do travel at a little less than the speed of light, for practical purposes you can ignore that. The time lag is close to negligible, even for large distances. The neutrinoes from SN1987a, for instance, arrived within seconds of each other, despite the differences in energy, and they were all quicker than the light, due to not having to worry about that pesky intersellar medium.