3 ms·

Wonderful pictures! The Super Kamiokande had a terrible engineering event where the delicate sensor bulbs shattered, and the pressure delta from one shattering

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. https://www.youtube.com/watch?v=YoBFjD5tn_E 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.

puzzledobserver 4mo 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 4mo 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.
  - pge 4mo 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.
    - zhubert 4mo ago
      Same! I worked on SNO’s neutral current detectors at LANL (as a student so mostly grunt work). Which project?
  - throwup238 4mo 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.
  - 4mo ago
- qnleigh 4mo ago
  I used to think this was the explanation, but I was told by a particle physicist that this is actually not correct. Unfortunately I don't remember the correct argument (and I'm not sure I understood fully it in the first place)
beezlebroxxxxxx 4mo ago
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 4mo 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.
  - wasting_time 4mo ago
    And a nuance that is easily lost: the different neutrino eigenstates/flavors travel at different velocities, because they have different mass, so the probability of detecting one flavor depends on the distance travelled. Essentially each neutrino travels in three different "waves", but is still one unit in a constant superposition between the three.
    - tines 4mo ago
      So neutrinos are changing mass and velocity constantly?
      - wasting_time 4mo ago
        I'm no physicist, this is just how I understood this thread; but AIUI it's better to think of the neutrino being in all three eigenstates simultaneously, and if any of the three "bump into something" then it collapses to just the one flavor.
pavel_lishin 4mo ago
I remember some of the videos in this playlist doing a very good job explaining neutrino oscillations, and what it means, but I don't remember which ones: https://www.youtube.com/playlist?list=PLCfRa7MXBEsqOlL_g6wTMDYXB0BmAcwmI https://www.youtube.com/playlist?list=PLCfRa7MXBEsqOlL_g6wTM... Maybe this one? https://www.youtube.com/watch?v=eBT1-dV1BTM https://www.youtube.com/watch?v=eBT1-dV1BTM
deleted 4mo ago
[deleted]

puzzledobserver 4mo 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 4mo 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.
- pge 4mo 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.
  - zhubert 4mo ago
    Same! I worked on SNO’s neutral current detectors at LANL (as a student so mostly grunt work). Which project?
- throwup238 4mo 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.
- 4mo ago
qnleigh 4mo ago
I used to think this was the explanation, but I was told by a particle physicist that this is actually not correct. Unfortunately I don't remember the correct argument (and I'm not sure I understood fully it in the first place)

beezlebroxxxxxx 4mo ago

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 4mo 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.
- wasting_time 4mo ago
  And a nuance that is easily lost: the different neutrino eigenstates/flavors travel at different velocities, because they have different mass, so the probability of detecting one flavor depends on the distance travelled. Essentially each neutrino travels in three different "waves", but is still one unit in a constant superposition between the three.
  - tines 4mo ago
    So neutrinos are changing mass and velocity constantly?
    - wasting_time 4mo ago
      I'm no physicist, this is just how I understood this thread; but AIUI it's better to think of the neutrino being in all three eigenstates simultaneously, and if any of the three "bump into something" then it collapses to just the one flavor.

pavel_lishin 4mo ago

I remember some of the videos in this playlist doing a very good job explaining neutrino oscillations, and what it means, but I don't remember which ones: https://www.youtube.com/playlist?list=PLCfRa7MXBEsqOlL_g6wTMDYXB0BmAcwmI https://www.youtube.com/playlist?list=PLCfRa7MXBEsqOlL_g6wTM... Maybe this one? https://www.youtube.com/watch?v=eBT1-dV1BTM https://www.youtube.com/watch?v=eBT1-dV1BTM

deleted 4mo ago

[deleted]