[puzzledobserver]

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]

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.

[adrian_b]

One can make separate detectors for electronic, muonic and tauonic neutrinos, because they take part in different reactions.

Given a flux of neutrinos, e.g. coming from the Sun or from a nuclear reactor, one can use the different kinds of neutrino detectors to estimate the total flux and the fractions of the three kinds.

With another set of detectors put somewhere else, at a great distance along the direction of propagation of the neutrino flux, i.e. where those neutrinos arrive later, one can measure again the fractions of the total flux.

If one measures different fractions, and knowing the propagation time between the 2 locations, one can conclude that oscillations exist and measure the frequency of the oscillations.

Nonetheless, this is much easier said than done, All neutrino experiments have extremely poor signal-to-noise ratios and all their results are affected by great uncertainties.

The theory about the existence of the neutrino oscillations had been originally proposed as an explanation for the fact that the flux of neutrinos coming from the Sun was about 3 times smaller than predicted by the modelling of the fusion reactions inside the Sun.

Later, experimental results from measuring the fractions of the different neutrino kinds at distant locations appeared to support the oscillation hypothesis.

[throwup238]

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]

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]

Same! I worked on SNO’s neutral current detectors at LANL (as a student so mostly grunt work). Which project?

[qnleigh]

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)