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SiempreViernes 4 hours ago [-]
For anyone wondering about the title, by "trap" they mean "detect destructively": there are no stable neutrinos in a bottle in this article.
stouset 3 hours ago [-]
That would be a wild thing to accomplish, given that neutrinos are created at relativistic speeds, have virtually zero mass, and don’t react with anything but gravity and the weak force.
Whatever gravity “trap” you make is going to pale in comparison to the gravity wells around us (earth, the sun, etc) and the weak force scales exponentially with energy. So a slow-moving neutrino would interact even less with the weak force than a relativistic one.
__MatrixMan__ 20 minutes ago [-]
Are there a bunch of slow neutrinos sloshing around near the center of the earth?
amelius 2 hours ago [-]
What if you make the trap move at relativistic speed?
Varelion 4 hours ago [-]
Damn it. Heart rate sky-rocketed from excitement.
anonymousiam 2 hours ago [-]
From the (captions under photographs) in the article:
'Located 2.1 kilometers underground in the Creighton mine in Ontario, Canada, the Sudbury Neutrino Observatory’s detector (left) was filled with “heavy” water, which features deuterium in place of hydrogen atoms. Its findings provided evidence that neutrinos can change, or “oscillate,” between different flavors.'
"China’s Jiangmen Underground Neutrino Observatory (JUNO), seen here under construction in 2023, is currently the world’s largest neutrino detector. It began collecting data in August 2025; one of its main goals is to determine the outstanding mystery of how heavy each flavor of neutrino is."
The second caption implies that some "flavors" of neutrino may be heavier than other flavors. The first caption says that neutrinos oscillate between different flavors. If the first caption is correct, then wouldn't each flavor of neutrino be just as heavy as the others?
cobbzilla 1 hours ago [-]
I also wonder this!
Some real physicist tell me what I’m getting wrong here:
neutrinos have mass but the magnitude is so infinitesimally small, and the oscillation smaller still, such that you’re bumping up against some fundamental properties of the universe and the oscillation is “borrowing” and “returning” some tiny amount of mass/energy from the vacuum.
2 minutes ago [-]
gattr 2 hours ago [-]
Could a physicist comment on this? I've been reading on the CNO cycle [1], where it says neutrinos produced in the beta-decay steps can have any share of the resulting energy. Does it mean the Sun is shrouded in a rarefied cloud of such low-energy neutrinos which failed to achieve escape velocity?
This is an interesting question, but it would be very difficult to verify.
Only neutrinos with an extremely low kinetic energy would have velocities much lower than that of light, and the fraction of such neutrinos from the total flux of neutrinos would be very small. If they did not escape Sun, most would be probably captured sooner or later by nuclei from the gases of the Solar atmosphere (i.e. chromosphere or corona).
mrguyorama 3 hours ago [-]
Wonderful pictures!
The Super Kamiokande had a terrible engineering event where the delicate sensor bulbs shattered, and the pressure delta from one shattering caused neighbors to shatter, in a chain reaction that destroyed large amounts of sensors.
>Neutrinos come in three different “flavors” (electron, muon, and tau) and can oscillate, or switch, between them. To do so, neutrinos must have mass
Why? What actually is "Neutrino oscillation" and why does it require the neutrino have mass? My already feeble understanding of particle and quantum physics always breaks down at these sorts of points.
How are we sure that the neutrino is in fact a single particle that should use the same sort of mathematical machinery as all others? Am I even asking a question that means something? I know literally every physicist ever graduated has spent time thinking everything in physics is wrong and tried poking at such ideas, so I guess I'm more interested in what those kids end up finding that brings them back to "No this makes more sense" of neutrinos in the standard model.
puzzledobserver 2 hours ago [-]
Disclaimer: I'm not a physicist.
For a particle to "oscillate", it must "experience" time. All massless particles travel at the speed of light. As a consequence of special relativity, they don't "experience" time.
Therefore, neutrinos must be traveling slower than light, and they must have mass.
mrguyorama 37 minutes ago [-]
Oh, duh. I can follow that logic now. The meat of my question is much dumber though:
How do we know the "Same" neutrino is oscillating? We don't even have concrete understanding of how they would have mass, and different existing concepts of how it could be are problematic.
There's so much the standard model isn't sufficient for, in terms of explanations and predictions and categorization, that it always feels odd to me when we shove another weird thing into the "Particle" bucket.
It's also a dumb complaint though. A lot of deficiencies probably come down to simply not having enough good data to distinguish different ideas. It's hard to get good data with something that "Barely interacts" with anything else, by definition.
Also maybe my complaint is entirely semantic, that a naturally unfinished or incomplete theory is presented as "We know". If you model a scientific theory developing over time, are we still so early that neutrino oscillation could actually be entirely different? Or do we actually have the data to demonstrate that "No, a singular neutrino absolutely changes to different flavors over time, nothing else could cause the effects we see in X, Y and Z demonstrations"?
Like, I have sky high confidence that the standard model captures and predicts things like electrons and protons and quarks extremely well, so it always feels dissonant when we see things get weird like this, but also nature doesn't promise us coherent rules, just consistent ones. Reality could very well be full of crummy edge cases.
Just sucks that I'll be dead before we really figure most of this stuff out.
Also WTF even is time.... Why does something that is in one state, sometimes, be in a different state.... Is it even real? You can travel through space because you can have a spacial velocity, and that velocity can change through forces acted upon you, but is it even possible for there to be an analogous set of forces that can change your "Time velocity"....
I'll have to buy my physicist friend a drink so I can have him laugh at me for weird, half baked philosophy questions that aren't really valid.
throwup238 9 minutes ago [-]
I'm not a physicist so take it with a grain of salt:
> If you model a scientific theory developing over time, are we still so early that neutrino oscillation could actually be entirely different? Or do we actually have the data to demonstrate that "No, a singular neutrino absolutely changes to different flavors over time, nothing else could cause the effects we see in X, Y and Z demonstrations"?
We are still early in the sense of "why neutrinos have mass" but the evidence for neutrino oscillation itself is very strong. The classic experiment is measuring the neutrino flux coming off of our sun: the total neutrino flux matches solar-model expectations but without neutrino oscillation, the electron neutrino flux does not, and the missing fraction depends on distance divided by energy.
The T2K experiment has measured the oscillation of a muon neutrino beam over about 300km and the Daya Bay experiments measured electron anti-neutrino oscillation from nuclear reactors over a distance of several kilometers. At this point the evidence required to overturn neutrino oscillation would have to be extraordinary.
> Like, I have sky high confidence that the standard model captures and predicts things like electrons and protons and quarks extremely well, so it always feels dissonant when we see things get weird like this, but also nature doesn't promise us coherent rules, just consistent ones. Reality could very well be full of crummy edge cases.
My understanding is that the mathematical machinery created to explain quark flavors is also used to explain neutrino flavors, so we're not dealing with a unique snowflake in physics.
pge 17 minutes ago [-]
With the caveat that it’s been almost 30 years since I worked on neutrino oscillation, and I was just a student at the time, the way to detect neutrino oscillation is to look at the ratio of different kinds of neutrinos. If those ratios are different from the ratios calculated to be produced by the reaction at hand (eg a collision in a particle accelerator), then you know some of the neutrinos changed flavor.
It's kind of useful to only think of these things as "particles" in a nominal sense. You need to adopt a "quantum imagination". I tend to think of them as a wave or field of probabilities of energy. It sounds weird, but similar to "spin", "flavour" describes a particular relationship between waves or fields of probabilities of energy as it moves through space over time.
A simplified summary: The discovered mass emerges out of this relationship between detection and probability.
tines 2 hours ago [-]
This is making it sound way more complicated than it is. Sibling comment is much better. Thing changes over time -> thing experiences time -> it's not going the speed of light -> it has mass.
ktallett 5 hours ago [-]
There is a good exhibit on this at the Miraikan in Odaiba, Tokyo. Detecting things and proving we detected what we detected we previously couldn't is always a fascinating exercise, especially whilst so much matter is still unrecognised.
semiquaver 3 hours ago [-]
HN automangled the title, should have a “how” at the beginning. The change makes the headline sound like this is news, but it’s just a description of neutrino detectors.
Whatever gravity “trap” you make is going to pale in comparison to the gravity wells around us (earth, the sun, etc) and the weak force scales exponentially with energy. So a slow-moving neutrino would interact even less with the weak force than a relativistic one.
"China’s Jiangmen Underground Neutrino Observatory (JUNO), seen here under construction in 2023, is currently the world’s largest neutrino detector. It began collecting data in August 2025; one of its main goals is to determine the outstanding mystery of how heavy each flavor of neutrino is."
The second caption implies that some "flavors" of neutrino may be heavier than other flavors. The first caption says that neutrinos oscillate between different flavors. If the first caption is correct, then wouldn't each flavor of neutrino be just as heavy as the others?
Some real physicist tell me what I’m getting wrong here:
neutrinos have mass but the magnitude is so infinitesimally small, and the oscillation smaller still, such that you’re bumping up against some fundamental properties of the universe and the oscillation is “borrowing” and “returning” some tiny amount of mass/energy from the vacuum.
[1] https://en.wikipedia.org/wiki/CNO_cycle
Only neutrinos with an extremely low kinetic energy would have velocities much lower than that of light, and the fraction of such neutrinos from the total flux of neutrinos would be very small. If they did not escape Sun, most would be probably captured sooner or later by nuclei from the gases of the Solar atmosphere (i.e. chromosphere or corona).
The Super Kamiokande had a terrible engineering event where the delicate sensor bulbs shattered, and the pressure delta from one shattering caused neighbors to shatter, in a chain reaction that destroyed large amounts of sensors.
https://www.youtube.com/watch?v=YoBFjD5tn_E
Unrelated:
>Neutrinos come in three different “flavors” (electron, muon, and tau) and can oscillate, or switch, between them. To do so, neutrinos must have mass
Why? What actually is "Neutrino oscillation" and why does it require the neutrino have mass? My already feeble understanding of particle and quantum physics always breaks down at these sorts of points.
How are we sure that the neutrino is in fact a single particle that should use the same sort of mathematical machinery as all others? Am I even asking a question that means something? I know literally every physicist ever graduated has spent time thinking everything in physics is wrong and tried poking at such ideas, so I guess I'm more interested in what those kids end up finding that brings them back to "No this makes more sense" of neutrinos in the standard model.
For a particle to "oscillate", it must "experience" time. All massless particles travel at the speed of light. As a consequence of special relativity, they don't "experience" time.
Therefore, neutrinos must be traveling slower than light, and they must have mass.
How do we know the "Same" neutrino is oscillating? We don't even have concrete understanding of how they would have mass, and different existing concepts of how it could be are problematic.
There's so much the standard model isn't sufficient for, in terms of explanations and predictions and categorization, that it always feels odd to me when we shove another weird thing into the "Particle" bucket.
It's also a dumb complaint though. A lot of deficiencies probably come down to simply not having enough good data to distinguish different ideas. It's hard to get good data with something that "Barely interacts" with anything else, by definition.
Also maybe my complaint is entirely semantic, that a naturally unfinished or incomplete theory is presented as "We know". If you model a scientific theory developing over time, are we still so early that neutrino oscillation could actually be entirely different? Or do we actually have the data to demonstrate that "No, a singular neutrino absolutely changes to different flavors over time, nothing else could cause the effects we see in X, Y and Z demonstrations"?
Like, I have sky high confidence that the standard model captures and predicts things like electrons and protons and quarks extremely well, so it always feels dissonant when we see things get weird like this, but also nature doesn't promise us coherent rules, just consistent ones. Reality could very well be full of crummy edge cases.
Just sucks that I'll be dead before we really figure most of this stuff out.
Also WTF even is time.... Why does something that is in one state, sometimes, be in a different state.... Is it even real? You can travel through space because you can have a spacial velocity, and that velocity can change through forces acted upon you, but is it even possible for there to be an analogous set of forces that can change your "Time velocity"....
I'll have to buy my physicist friend a drink so I can have him laugh at me for weird, half baked philosophy questions that aren't really valid.
> If you model a scientific theory developing over time, are we still so early that neutrino oscillation could actually be entirely different? Or do we actually have the data to demonstrate that "No, a singular neutrino absolutely changes to different flavors over time, nothing else could cause the effects we see in X, Y and Z demonstrations"?
We are still early in the sense of "why neutrinos have mass" but the evidence for neutrino oscillation itself is very strong. The classic experiment is measuring the neutrino flux coming off of our sun: the total neutrino flux matches solar-model expectations but without neutrino oscillation, the electron neutrino flux does not, and the missing fraction depends on distance divided by energy.
The T2K experiment has measured the oscillation of a muon neutrino beam over about 300km and the Daya Bay experiments measured electron anti-neutrino oscillation from nuclear reactors over a distance of several kilometers. At this point the evidence required to overturn neutrino oscillation would have to be extraordinary.
> Like, I have sky high confidence that the standard model captures and predicts things like electrons and protons and quarks extremely well, so it always feels dissonant when we see things get weird like this, but also nature doesn't promise us coherent rules, just consistent ones. Reality could very well be full of crummy edge cases.
My understanding is that the mathematical machinery created to explain quark flavors is also used to explain neutrino flavors, so we're not dealing with a unique snowflake in physics.
Maybe this one? https://www.youtube.com/watch?v=eBT1-dV1BTM
A simplified summary: The discovered mass emerges out of this relationship between detection and probability.