Neutrino Oscillations Confirmed 122
mfg writes "The Sudbury Neutrino Observatory has found evidence that neutrinos can change type between the Sun
and Earth. See the
BBC news story for more details."
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Neutrino Oscillations Confirmed
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"The great question... which I have not been able to answer... is, `What does woman want?'" -- Sigmund Freud
Re:Why are the neutrinos interesting? (Score:2, Interesting)
Re:Why are the neutrinos interesting? (Score:3, Insightful)
One of the most commonly repeated "geek tenets" is that coding scratches an itch. People write code because they enjoy it, it's a challenge, and hey, even if no one else ever finds the resulting code useful, it was fun, right?
Same thing here. People want to know stuff, they want to understand how the universe works. That's why people study things like this. Knowing how the sun is powered, and the details of the nuclear reactions that take place, may never lead to any practical application, but that doesn't matter. Humanity is enriched merely by possesing the knowledge. It's a bit like solving puzzles - you gain nothing by doing so but the satisfaction of doing it.
Besides, who knows what applications this sort of research could lead to? The laser was sat around in reasearch labs for years before anyone thought of anything to do with it. Now it's a central part of the entertainment and computing industries.
Still, I guess I'm biased - my degree is in Physics, and I've always been fascinated by astronomy.
Re:Why are the neutrinos interesting? (Score:3, Insightful)
For example, right now there's this Dark Matter bit... we can use modern physics to explain everything except, oh, 99% of the universe. So clearly better understanding of the universe (on astronomical and sub-atomic) scales is needed.
Last time there was a major understanding of the sun, it was probably 'hey, stars are powered by hydrogen fusion'. Which helped nuclear research.
So think of sun/star research as 'really big remote lab work' and it makes sense. It's not just abstract, it's "applied, big scale".
Pure research always pays, you just can't tell in advance how, when, and to whom
Re:Why are the neutrinos interesting? (Score:1)
Have past scientific advances resulted in practical societal benefits, only a Luddite would say no.
Will current science yield similar benefits? Regardless of past history, this is a matter of faith. Granted that past discoveries such as lasers, semi-conductors, etc. have not been instant winners, requiring many years for a practical application.
There is a difference in that the energy levels are so far from normal human experience (being very deadly to us, they will remain so) it is reasonable to doubt that there will be an eventual payoff, or at least one that could be useful in a reasonable time frame.
It is reasonable to consider using the money spent to fund this type of research for something more practical in our lifetimes. And yes, I may be biased -- I studied engineering, not physics.
I don't dispute the premise that science and knowledge have intrinsic value. Just a recognition this is not sufficient to justify an infinite stack of research bucks. Have faith in science, just don't expect everyone else to always be ready to fund your faith.
Re:Why are the neutrinos interesting? (Score:1, Insightful)
Re:Why are the neutrinos interesting? (Score:5, Interesting)
Re:Why are the neutrinos interesting? (Score:4, Interesting)
It's called science. You make a hypothesis, and you try and prove it by experimentation. Simple really.
With the sort of attitude shown here, Einstein would never have bothered looking at discrepancies in Newton's laws of motion and gravitation, and there would be no theories of relativity. Heisenberg/Bohr/Planck (and all the others) would never have looked at discrepancies in black body radiation etc and quantum theory would never have been thought of. And then I wouldn't be writing this, because semiconductors would never have been discovered.
Just because there's no immediate application in a particular field doesn't make it important. Stop thinking of that great big $ sign.
Re:Why are the neutrinos interesting? (Score:1)
[Nitpicking mode]
Actually, you can never prove a hypothesis or theory, you can only prove it wrong, and thus work towards a better theory.
[/Nitpicking mode]
Re:Why are the neutrinos interesting? (Score:1)
Newton's laws of motion are laws because they are true, at least at normal scales and velocities. Once you get to the microscopic scale, or within 0.1c (10% speed of light) they become inaccurate. This is when quantum physics (which is still theory) and relativity (again, still theory) take over.
Both quantum physics and relativity have enough descrepancies to not be widely regarded as laws. Nothwithstanding the fact that they are mutually exclusive (they do not work together).
Re:Why are the neutrinos interesting? (Score:1)
Re:Why are the neutrinos interesting? (Score:5, Informative)
No. This is probably the single most common misconception about physical science; but a misconception it is.
A physical "law" is not a "theory that has been proven". The word "law", in physical science, is used to describe relations between independently observable properties of systems that have been detected through experimentation or observation. Thus we have Newton's Law of Gravitation, which relates an external observable property of an object (the force upon it) to intrinsic but observable properties of that object (its mass, the masses of other objects, and the distances between them); this is a physical law even though, strictly speaking, it isn't true (as we now know that it provides only an approximation, which holds reasonably well over certain domains of length and mass scale).
The fact is that theories are never proven to be true in science. A theory can be falsified, but can never be proven true. This is because no matter how much evidence you have collected in favor of a theory, it is always imaginable that tomorrow, someone will observe some phenomenon that contradicts it. We have tons and tons of evidence supporting conservation of momemtum in systems isolated from external forces; but no matter how much evidence we have, it is logically impossible for me to guarantee that tomorrow someone won't do a robust experiment that shows violation of conservation of momentum. I'll bet all the money in the world that won't happen, I'm confident it won't happen; but I cannot logically assert with 100% confidence that it cannot happen. You can never say with logical certainty what will happen in an experiment until you do the experiment; and because of this, scientific theories are not proven true. Instead of being "proven to be true," scientific theories are "supported by the weight of accumulated evidence"; it is the degree to which that accumulates evidence is convincing that determines the statue of the theory it supports.
Re:Why are the neutrinos interesting? (Score:1)
The laws of thermodynamics are taken to be laws because so many experiments have been done that support it, that it's 99.999999999% certain. Saying that you cannot "logically assert with 100% confidence that it cannot happen" may indeed be logical but it adds nothing to a debate about whether a law holds true or not. It would be scientific to say "I assert this cannot happen because...". This is how science moves forward, not by arguing about logic.
Saying that, I do of course agree that it's always worth looking for faults in "laws", because you never know what you might find. You just need a good reason to do so...
Re:Why are the neutrinos interesting? (Score:1)
It's correct that for a relationship to be asserted as a "law," those doing so have a high degree of personal confidence that it provides an accurate description of the relation between the observables contained within. In that sense, they are "held to be true," just as I hold that conservation of momentum is "true." I very very strongly think it's right. But that's not the same thing as "proven." I can believe that a physical law is inviolable; but I cannot possibly show that it's inviolable, since to do so would require testing that law in the infinity of possible circumstances. So "held to be true/inviolable" is a social statement about we scientists, rather than a statement of scientific fact.
Saying that you cannot "logically assert with 100% confidence that it cannot happen" may indeed be logical but it adds nothing to a debate about whether a law holds true or not. It would be scientific to say "I assert this cannot happen because...". This is how science moves forward, not by arguing about logic.
I disagree strongly. In regard to your last point, I'll simply say that in my job (as an astrophysicist), I've worked with hundreds of other researchers, all of whom have done a decent job of moving the field forward through the process of putting forward theories and either falsifying them or accumulating evidence in their favor, while understanding that the theories in question are never proven to be true.
You originally asserted that when a theory is proven, it becomes a law. The reply that "in fact, a law is not a theory which has been proven to be true, especially since theories are never proven to be true in science" is not just some silly philosophical statement or dispute about a fine point of logic, but has crucial importance. I mentioned that it's a quite common misconception; that misconception has tangible negative ramifications.
As an example of the importance of the common misconception of which we speak. . .in the U.S., we frequently hear people who are uneducated about the fact that scientific theories are never proven true refer to the theory of evolution with "it's just a theory! It hasn't been proven to be true!" Strictly speaking, this is correct -- the theory of evolution has not been proven to be true. But this is a scientifically uninteresting point to make, because it never will be proven to be true, because no scientific theories are ever proven to be true. Similarly, gravity is `just a theory'; the theory of gravity has not been proven to be true, either. We put stock in our scientific theories not because they are ever proven true, but simply because we have accumulated a compelling degree of evidence in their favor.
Re:Why are the neutrinos interesting? (Score:1)
But again, I totally agree with half of what you say, regarding the certain people's attitude toward scientific theories. It drives me up the wall when I hear things like "But no-one's ever seen a monkey evolve into a human, therefore Darwin must be wrong!" (check out the earlier post about OS X being the OS of the Devil for morer on this).
And did you turn to Astrophysics after the bass-playing gig fell through?
Re:Why are the neutrinos interesting? (Score:2, Insightful)
Admittedly, it may be hard for some people to understand, but knowledge is, by many people, including myself, valued over practical application.
I'd rather know that the neutrinos are changing type en route to earth and have no practical application for it, than not know at all.
Why? Who knows. Maybe it's the engineer in me... "Because I can."
Re:Why are the neutrinos interesting? (Score:2)
Hey, that's the thing with research. You never know what applications your work will have.
If you know the application, your work is usually called 'engineering'.
Don't remember who said it, don't remeber the exact wording, but it's something to think about: "There is nothing more applicable than a good theory!" (Perhaps it was Einstein's answer when a journalist asked him how this relativity-thingie was supposed to be used?)
Anyway, what this is useful for? No idea, what's a neutrino?
Re:Why are the neutrinos interesting? (Score:5, Informative)
Re:Flavors of neutrons (Score:1)
Why was Copernicus on to something? (Score:1)
Most people, though, would say that it's better to live in knowledge of our world than ignorance of it, no matter the practical benefit.
--N
Re:Why was Copernicus on to something? (Score:1)
1) Solar probes that accurately predict when solar storms will hit Earth and disturb communications, etc.
2) Any practical application of space travel. Admittedly we don't much of this yet. Mining asteroids, colonies on moon or other planets, etc.
3) Enabling a basic understanding of gravitation. Commonly used in things such as discovering oil fields to building and maintaining a GPS network.
I'm sure there are many more if I were to take the time to consider.
Re:Why was Copernicus on to something? (Score:1)
No no no no. (Score:1)
No, that ISN'T the point.. although it IS another reason to do pure research.
The point is: it's worth knowing things for reasons OTHER than practical. To give even more obvious examples: we want to know if God exists even if he DOESN'T answer prayers. We want to know if the universe will collapse even if we're not around to see it. We want to know how the Romans dug wells even if we have better ways to do it ourselves. We want to understand Napoleonic history, even if it's not applicable to the modern age.
We want to know a lot of things, becuase knowing them gives us insight into our world, insight into ourselves. They are things worth knowing for the sake of simple understanding, not having ANYTHING to do with practical application.
Those of you out there who are purely pragmatic about science should ask yourselves why you bother. What is the use of practical things if they don't serve some greater utility? We don't need computers to feed ourselves or house ourselves; survival or success should not be humanity's only motive. For some, the motive might be religious or hedontistic, but for myself, I belive in an _academic_ progressivism, where learning about our universe is the end, not the means.
---Nathaniel, waxing philisophical
Re:Why are the neutrinos interesting? (Score:1)
Here's the meat of the article: The ratio of electron neutrinos detected to the total number of neutrinos detected didn't match the sensible models of nuclear reactions in the Sun. There just weren't enough of them. Now, they have found that some of the muon and tao neutrinos they are detecting actually started electron neutrinos, and changed on the way. It remains to be seen, however (if it ever can), whether the conversion rate can explain enough missing electron neutrinos to match the theories.
Models of the processes inside the sun (Score:1)
The results shown in this article are important because the evidence means new areas to study.
Re:Why are the neutrinos interesting? (Score:2)
We need to explore these cool sounding particles so we can have devices like "neutrino blasters", "neutrino combobulators", and "neutrino themed cocktail parties".
I mean, we probably would never have electricity if electrons were called "gurdlehumps".. think about it!!
Did they really change... (Score:1)
Re:Did they really change... (Score:1)
Boredom? (Score:4, Funny)
Point? (Score:1)
The equipment they use is interesting. Yet again its a shame i dont understand it...guess i have to get my ex-girlfriend to explain it to me...
There seems to be no cover of what effects proving this is...or is it like:
"Hey lets build a lab on how to mesure the perfect time to dunk a biscuit"I an't tryin to be a troll, just want to know what effect this will have on future research
Re:Point? (Score:4, Interesting)
There is a good deal of tension between advocates of basic versus applied research, and there needs to be a better dialog. Currently it is a bunch of people throwing around assumptions about the merits of both types of research, but no one seems to really engage the other. (IMHO).
As an aside, there was a link [bbc.co.uk] from the article about the Japanese detector. Seems that one of the tubes blew which set of a cascade that destroyed most of the remaining tubes. I can't imagine the boom that one made...
Re:Point? (Score:1)
1000 points of light (Score:5, Insightful)
Hopefully you won't find it difficult to answer that question, as you power up your Pentium IV processor to hack some PERL code, crunch some numbers to decode your encrypted email, and look at the latest NASA gallery images represented on your monitor as a rasterized RGB image driven by an electron beam.
And as you insert a CD into the CD player which is read by a GaAs laser and decrypted by more microelectronics, so you can listen to the solid-state (or vacuum-tube if you prefer) amplifier drive a magnetic speaker coil for your listening pleasure.
And then as you get in your car, with the engine ignited by carefully-timed spark plug firings, where you turn on the radio and pick up frequency-modulated electromagnetic radiation and decode it into stereo sound, again sent to an amplifier and speakers for your listening pleasure.
So, you see, it's hard to determine, a priori, the benefits of certain scientific advances and the effects they'll have on civilization. Neutrino oscillations are important because they put another piece into the puzzle that high-energy physicists are trying to solve relating how all the elementary particles fit together.
Some potential uses for this might deal with gaining further insights into nuclear power and better ways to do it. Specifically, fusion power. The sun is a fusion reactor, but scientists haven't been able to efficiently harness fusion power here on earth yet. This neutrino puzzle helps verify some of the hypotheses scientists had about nuclear processes in the sun that weren't fully understood or adequately measured with older neutrino counters.
It might also help long-range communication. Neutrinos can pass through the earth without being affected, and scientists had once tried to use this method for talking to submarines on the other side of the planet. The obvious problem is how do you detect said neutrons. I think I heard something that they were able to make a receiver that could receive data at a rate of a few bits per day. Not very efficient. Well, learning more about neutrons and their oscillations might give insight into ways to improve neutrino communications.
There are most likely many other things too, that we just don't know about or don't have use for. Maybe they'll prove efficient for long-range communications to other planets, and possibly for quantum encryption during these communications. We just don't know yet, but if we don't try we'll never know.
They beat em (Score:5, Informative)
For the people who have no idea what neutrinos oscillating is about - try here. [fnal.gov] It gives a good overview, made so someone like me could even understand it.
Not Pointless (Score:1)
Re:They beat em (Score:2)
Well they get an in flight meal? First class or coach?
Re:They beat em (Score:2)
Not at all (Score:5, Informative)
In fact, there is a large quantity of work going on in this field. Current experiments include KamLAND, Borexino, Opera, NuMI-MINOS, Super-Kamiokande (when they finish their repairs in a year or so), K2K (KEK to Super-K), MiniBOONE the new JHF facility, plus a bunch more I'm forgettting.
There are several reasons for all this activity. First, there are at least two different types of oscillaitions. (The naive and over-simplified theory is that there is nu-electron to nu-mu oscillation, and nu-mu to nu-tau oscillation, the first of which is seen by SNO, the second of which is seen by atmosphereic neutrinos and by the beam experiments). There may be a third mode, which implies a new variety of neutrino (nicknamed 'sterile' for various reasons).
In addition, we're looking to prove that our theory about the oscillations is correct; that they really oscillate in the way we think they do (i.e. change back and forth between flavours on a given time scale that is dependent on energy and suchlike). We want to know the exact parameters in the theory, so the theorists have some hard numbers to much on to make better overarching theories. And, there's always the possibility that something entirely new will crop up in these studies.
(A note on that last: modern neutrino detectors were born out of eariler attempts to build proton decay experiments... but the neutrinos kept getting in the way! On the 'don't beat 'em, join 'em' approach, people started looking at the neutrinos themselves with more interest.)
--Nathaniel, prowling his favourite topic.
Re:So what are the implications? (Score:2)
Is there an upper/lower limit to the nu mass? (I'm more of a cosmologist - and nu mass amounts are interesting, especially in working out the virial relations for Galactic clusters... and geometry of the Universe.)
Re:So what are the implications? (Score:1)
It's time for "nu mass"
nu-hu-hu mass...
I'm so ashamed.
Re:So what are the implications? (Score:2, Informative)
Of course, this is only the mass _difference_. There's very little direct mass evidence, so the maxixum mass could still be up high enough to be more interesting, but it's viewed as unlikely.
---Nathaniel
Re:So what are the implications? (Score:1)
The latest SNO results prove (i.e. show evidence at a very high probability) that the deficit of neutrinos is due to flavour-changing: that is, the neutrinos were all there, but the gallium experiments just couldn't see them. As a matter of fact, SNO nails the Standard Solar Model predictions (J. Bachall et al) right on the nose, so it all remains pretty convincing.
---Nathaniel
Re:So what are the implications? (Score:2)
Omega_nu h^2 = (sum of neutrino masses) / 93.5eV
(Peacock 1999 p.281)
For h=0.7 and a total neutrino mass of 0.1eV, that gives Omega_nu=0.002, which is negligible for cosmology (and probably for structure formation too, though I'm not sure exactly how much HDM you need to add to start wiping out small scale structure).
Of course, if the neutrino mass is large enough that they're cold when they decoupling, all bets are off...
[TMB]
Re:They beat em (Score:2, Informative)
This is not a pointless experiment. In both experiments that the article mentions (SNO and SuperKamiokande) neutrinos are produced by a natural process (either nuclear reactions in the Sun or cosmic rays in atmosphere). There is always a possibility that we don't understand these natural processes good enough and that we misinterpret the data.
In these planned terrestrial neutrino oscillation experiments (such as NOMAD [nomadinfo.cern.ch], K2K [neutrino.kek.jp], OPERA [web.cern.ch], MINOS [fnal.gov], etc.) neutrinos will be produced in controlled reactions on Earth, making interpretation and measurements easier, more precise and more model-independent.
Why this matters.... (Score:5, Insightful)
Here's [aip.org] a link to some background on neutrinos, and particle physics in general (from the American Institute of Physics).
The basic idea is this: neutrinos seem to be fundamental particles. The more we understand about them (properties, interactions, etc) and the other elementary particles, the more we understand about how the universe works. This usually has "practical" applications in fields like astronomy and cosmology first. But don't worry, eventually there will be nice day-to-day applications (neutrino toasters, etc
Re:Why this matters.... (Score:5, Interesting)
At normal neutrino flux levels, it'd take several times the lifespan of the universe for neutrinos to deposit even the tiniest amount of energy into a slice of bread. Consider the fact that many billions have passed through your body in the time you've been reading this comment. It's unlikely a single one of them would actually collide with a particle in your body.
A neutrino toaster would probably need the total neutrino output of the sun to toast a slice of bread in a reasonable time period - and if you've got that, why not just stick your bread on a real long fork and toast it over the sun's corona
Re:Why this matters.... (Score:1)
My "neutrino toaster" could just be a box where neutrinos passing thru WOULD interact with the slice of bread inside. Since there are more than 4x10^10 neutrinos / cm^2 incident on the earth every second, I think it could be a handy energy source. Why use a long fork when then energy will come to you? A lot more convenient than solar power, etc - the neutrinos pass right thru the atmosphere, even the whole planet! No worries about power when the sun goes down....
Re:Why this matters.... (Score:2, Funny)
Re:Why this matters.... (Score:2)
Re:Why this matters.... (Score:2, Interesting)
Lets ignore the technical impossibilities for a second here.
Actually we already have a good application already. we have proved that the sun is working as we expect. There was two possibilities for the missing neutrino's.
1. The theories were wrong
2. The sun was very ill.
Personally I feel a lot richer for knowing 2 is not the case.
Can we use this technology as a way to monitor the sun?
Re:Why this matters.... (Score:1)
This is true. Most people will "experience" a neutrino collision in their body once or twice in their lifetime. Of course, you'll never know it when it happens.
If there were a wall of solid lead, 1 light-year thick, out in space, only 50% of the neutrinos passing through it would actually collide with a lead atom. The other 50% would pass right through as if it weren't there.
Neutrino interactions and ball bearings (Score:2, Informative)
"It all depends on what you mean by 'hit' of course, seeing as matter consists almost entirely of nothing at all. The chances of a neutrino actually hitting something as it travels through all this howling emptiness are roughly comparable to that of dropping a ball bearing at random from a cruising 747 and hitting, say, and egg sandwich."
Also incidently, the neutrino toaster is not an invetion, it's a discovery: being close to a supernova would make you feel mighty warm, even if you did have shielding to protect you from the light and the matter shockwaves. Supernovae release 90% of their energy as neutrinos.
---Nathaniel, on the Neutrino Prowl, co-author on the recent SNO papers.
Supernovae (Score:2)
They do? How was this discovered?
Re:Supernovae (Score:1)
The idea is a collapsing star is opaque, like a light bulb painted black: the light is being made, but can't get out. Because of the very high temperatures and the density of the neutron soup in the centre, making neutrinos by pair-production becomes a method for the supernova to shed all that energy without using photons.
This is in addition to the neutronization burst that comes at the start, when the neutron star is formed.
---N
Re:Neutrino interactions and ball bearings (Score:2)
Back then, there was an article saying that people on Earth averaged one or two neutrino interactions in their bodies just from 1987A. Based on that, the energy of the interaction, and the good old inverse square law, I figured you'd get a lethal dose of radiation (500 REMs) at about 12 AU from the supernova. At Earth's distance, it might even be enough to kill you before the blast vaporizes you.
I've since similar numbers in other places, so I guess I didn't drop a decimal point anywhere.
Re:Why this matters.... (Score:1)
If there were a wall of solid lead, 1 light-year thick, out in space, only 50% of the neutrinos passing through it would actually collide with a lead atom. The other 50% would pass right through as if it weren't there.
There is something I would like to ask you very smart people. Would there be any way you can generate neutrinos in a manner so that you could piggy back information on them and detect that information at some distance? Kind of the way radio works. If so, it would be really nice because dense objects such as the earth and buildings would no longer be a problem for communications.
Just a thought.
God that's morbid. (Score:1)
for those too slow to avoid the slashdotting (Score:4, Informative)
Experiment confirms Sun theories
The SNO was constructed to solve a mystery
By Dr David Whitehouse
BBC News Online science editor
Neutrinos - some of nature's most elusive sub-atomic particles - do change their properties as they travel through space.
We are much more certain now that we have really shown that solar neutrinos change type
Prof Dave Wark, University of Sussex New evidence confirms last year's indication that one type of neutrino emerging from the Sun's core does switch to another type en route to the Earth.
This explains the so-called solar neutrino mystery, which has had scientists puzzled for 30 years - why so few of the particles expected to emerge from the nuclear furnace in our star can actually be detected.
The new data mean the reactions put forward by physicists to describe how the Sun works are correct.
The data were obtained from the underground Sudbury Neutrino Observatory (SNO) in Canada.
Going underground
Neutrinos are ghostly particles with no electric charge and very little mass. They are known to exist in three types related to three different charged particles - the electron and its lesser-known relatives, the muon and the tau.
Electron-neutrinos are created in the thermonuclear reactions at the solar core. Because these reactions are understood, it has been possible to estimate the number of electron-neutrinos that should emerge from our star.
But it has baffled scientists for decades as to why just a third of this expected number could actually be detected.
Using the underground Sudbury neutrino detector, an international group of researchers has been able to determine that the observed number of electron-neutrinos is only a fraction of the total number emitted from the Sun - clear evidence that the particles change type en route to Earth.
SNO Project Director, Dr Art McDonald, of Queen's University, Canada, said the number of electron-neutrinos detected combined with the numbers of other types picked up at Sudbury gave a total that was consistent with scientists' understanding of the nuclear reactions occurring at the Sun's core.
All types
The Sudbury Neutrino Observatory is a unique neutrino telescope, the size of a 10-storey building, two kilometres underground, down a mine in Ontario.
The SNO detector consists of 1,000 tonnes of ultrapure heavy water, enclosed in a 12-metre-diameter acrylic-plastic vessel, which in turn is surrounded by ultrapure ordinary water in a giant 22-metre-diameter by 34-metre-high cavity.
The observatory detects about one neutrino per hour
Outside the acrylic vessel is a 17-metre-diameter geodesic sphere containing 9,600 light sensors or photomultiplier tubes, which detect tiny flashes of light emitted as neutrinos are stopped or scattered in the heavy water.
At a detection rate of about one neutrino per hour, many days of operation are required to provide sufficient data for a complete analysis.
Because SNO uses "heavy" water - the hydrogen atom in the water molecule has an extra neutron - it is able to detect not only electron-neutrinos through one type of reaction, but also all three known neutrino types through a different reaction.
Very accurate
Dr Andre Hamer, of the Los Alamos National Laboratory, US, said: "In order to make these measurements, we had to restrict the radioactivity in the detector to minute levels and determine the background effects very accurately to show clearly that we are observing neutrinos from the Sun."
The research not only improves our understanding of the Sun but of the elusive neutrinos as well.
The latest results, entirely from the SNO detector, (and which have been submitted to Physical Review Letters) are said to be 99.999% accurate.
Dr MacDonald said: "The SNO team is really excited because these measurements enable neutrino properties such as mass to be specified with much greater certainty for fundamental theories of elementary particles."
Mass differences
This announcement is confirmation of indications released in June 2001 that suggested that it was highly likely that neutrinos changed type on their way from the Sun.
However those conclusions were always tentative because they were based on comparisons of results from SNO with those from a different experiment, the Super-Kamiokande detector in Japan.
Professor Dave Wark, of the University of Sussex and the Rutherford Appleton Laboratory, UK, commented: "Whenever a scientific conclusion relies on two experiments, and on the theory connecting them, it is twice as hard to be certain that you understand what is going on.
"We are therefore much more certain now that we have really shown that solar neutrinos change type."
Professor Hamish Robertson of the University of Washington, US, added: "There's absolutely no question the neutrino type changes and now we know quite precisely the mass differences between these particles."
Old news?? (Score:1)
Re:Old news?? (Score:1)
Re:Old news?? (Score:2, Funny)
This was the anouncement of the atmospheric neutrino results which pinned down neutrino mixing between muon and tau nus better than ever before.
SK also sees solar nus but only the electron neutrinos. In addition to the electron neutrino, SNO can also see the sum of all solar neutrino types (ie, the electron type as well as other types that the e-type may have oscillated to). Their first result relied on SK's measurement of the electron type nus because SNO has a smaller mass, thus lower count. The latest announcement appears to be stating that they have collected enough events that they can have a similar result as before but with out relying on some of SK's data.
You lost me a long time ago. (Score:4, Funny)
Re:You lost me a long time ago. (Score:3, Funny)
All the neutrinos are born Catholic, but only a third of them are Catholic by the time we detect them. The rest oscillate to other faiths, which are also known to have mass, just in different amounts.
SNO / Laurentian Press Release from 18 April (Score:3, Informative)
New scientific results from the Sudbury Neutrino Observatory to be announced
April 18, 2002
(Sudbury, Ontario) - Scientists from Canada, the United States and the United Kingdom, working at the Sudbury Neutrino Observatory (SNO), a unique underground laboratory built to provide insights into the properties of neutrinos and their emission from the core of the Sun, will submit a scientific paper with important new results later this week. They will announce these research findings in a scientific presentation by Dr. Andre Hamer on Saturday, April 20, at the Joint Meeting of the American Physical Society and the American Astronomical Society in Albuquerque, New Mexico. A copy of the first scientific paper and news release summarizing SNO's findings and their importance will be posted on the SNO website (www.sno.phy.queensu.ca) at 1:20 p.m EDT (10:20 a.m. PDT) on Saturday, April 20. A summary talk on the implications of these neutrino measurements will be presented by Dr. John Wilkerson on Monday, April 22, at the same conference.
"We look forward to this opportunity to share these new findings with the scientific community and the general public," says Dr. Art McDonald, SNO Project Director and member of the Department of Physics at Queen's University. "For the first time, we are reporting on an important neutrino reaction in the SNO detector - a reaction in which all known neutrinos participate, regardless of their type. The successful observation of these neutrino signals has been a chief goal of the years of intense work by a collaboration of close to 100 scientists at 11 universities and national laboratories in Canada, the United States and the United Kingdom, and we are very pleased with the quality of the data obtained."
In June 2001, the SNO scientific collaboration announced definitive results based on two other reactions seen in the SNO detector, and on measurements at the SuperKamiokande neutrino detector in Japan, establishing that neutrinos from the Sun change from their original electron neutrino type, to a mixture of electron and other (mu or tau) neutrino types. The new data from the Sudbury Neutrino Observatory to be announced on April 20, enables this question to be addressed accurately from data obtained entirely from SNO, and is expected to enhance significantly our understanding of these important properties of neutrinos from the Sun and of the Sun itself.
Additional information about the conference presentations, the SNO laboratory, the neutrino measurements being made and the participating institutions can be found at www.sno.phy.queensu.ca [queensu.ca].
Overview over current neutrino oscillation results (Score:1)
Neutrino MASS?? (Score:2)
I suspect they DO, which is a pain in the ass as I bet a million pounds in 1995 that they would be proven to be massless by 2005. Jesus! The stuff that seems important when you're at University!
Better start saving!
Re:Neutrino MASS?? (Score:2, Interesting)
But it is important. . . isn't it? If I recall my physics correctly, neutrinos with mass = closed universe.
It's funny when you think about it, that probably the smallest particle in the universe will decide its fate. . . but it's true. Pretty amazing stuff, physics.
Re:Neutrino MASS?? (Score:1)
I remember hearing the same thing you mentioned - that the shear number of neutrinos in the universe meant that the universe would be closed if they had mass.
Interesting. I wonder if anyone is doing prominent work on this question...
Re:Neutrino MASS?? (Score:1)
Local Colour (Score:2, Informative)
Stompin' Tom Connors even wrote a song [geocities.com] to prove it!
There are occasional tours of the SNO site (usually for academics and visiting dignitaries) but you have to set aside a large block of time just to allow for transit time down and back up.
Acutely interesting, but where's the detail??? (Score:2, Insightful)
As a debugging freak and mechanical moron, I'm curious why they're so sure that the extra muons and gluons are coming from the sun, versus being sourced from the fusion of a million billion stars in the universe? Do we have proof that detection levels rise when the sun is positioned directly over the NDS's - I doubt even the mass of the earth shields the station from a tiny percentage of such tiny bits, leaving me wondering...
I'm sure that there's some statistical 3D reasoning behind our certainty, like "the sky's dark at night because the universe is expanding, dork!" - same reasoning applies here? If so, we're using the same reasoning which applies to photon saturation to neutrinos, and we can be sure that's a valid assertion? (I.E. dark matter isn't going to present a barrier to nuetrinos, correct? But a sheet of paper will block all of the light from a starry night, so shouldn't the level of neutrino saturation be significantly higher than that of photons?)
Hey, I'm just a backyard mechanic and C code tweaker, but these are questions I don't see being asked in the public domain... maybe a physics geek can explain it. If so, can you also describe the rate at which these suckers are chugging along through the universe, and maybe how we figured what their relative speed is?
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Lord of the satanicult: we love everything but science, coding, small fuzzy rodents and the PLO, cuz they bedevil the hell out of our intellect...
Re:Acutely interesting, but where's the detail??? (Score:2, Informative)
Re:Acutely interesting, but where's the detail??? (Score:3, Informative)
Actually the day/night ratios detected at SNO
is more complex than this, the neutrino capture
cross section in matter is so small that the
even the whole mass of the earth doesn't block
a signicant fraction of the neutinos, the detected
flux of 1 neutrino per hour at SNO as a testament
to the vest number of neutrinos emitted by the
sun.
Instead what is happening is that (according
to theory), the neutrino oscillation rate becames
signicantly increased while the neutrino is
travelling through matter, so that at night
detented particles contains less electron neutrinos and more of the other types.
Oh, and finally, the neutrino captured in SNO emit a cone of UV light (checknov radition), and
the cone points in the direction the neutrino
came from, so scientist at SNO can have a good
idea weather the neutrinos came from the sun or
from deep space.
Re:Acutely interesting, but where's the detail??? (Score:1)
Can someone explain this to me? (Score:2)
How does precisely measuring a number that is 1/3 of that predicted by the solar neutrino model prove that the neutrinos are changing and not that the model is incorrect?
Isn't that a bit like publishing Hubble's constant to 800 decimal places, but knowing that your answer is only accurate to +/- 10 orders of magnitude?
Re:Can someone explain this to me? (Score:2)
[TMB]
"sub-types"? arrrrg (Score:1)
(Actually, subtyping may be fine for modeling nature, since God doesn't request changes in natural laws anywhere near as often as PHB's change business rules, strategies, and organization.)
Re:I should have paid more attention (Score:1)
Re:What kind of proof is this? (Score:1)
So SNO isn't seeing radioactive decay from the D2O. However, there is a lot of sorting the wheat from the chaff that needs to be done -- SNO sees all sorts of things like muons, radioactive decay from (extremely small) trace amounts of elements like radon, etc. Predictions of what a neutrino event in the detector should look like are used to determine what actually has a high probability of being a neutrino. A muon event, for instance, is far more energetic than a neutrino event, and actually looks nothing like a neutrino event.