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.
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.
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.
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.
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.
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)
No. PyPy development was ongoing long before the first release. The first intact commit in the PyPy repo is from February 2003: https://github.com/pypy/pypy/commit/6434e25b53aa307288e5cd8c....
And that commit indicates there's been development going on for a while already. The commit message is:
"Move the pypy trunk into its own top level directory so the path names stay constant."
PyPy migrated from Subversion to git at some point. Not sure how much of the history survived the migration.
That claim appears to contradict the second-system effect [0].
The observation is that second implementation of a successful system is often much less successful, overengineered, and bloated, due to programmer overconfidence.
On the other hand, I am unsure of how frequently the second-system effect occurs or the scenarios in which it occurs either. Perhaps it is less of a concern when disciplined developers are simply doing rewrites, rather than feature additions. I don't know.
I won't say the second-system effect doesn't exist, but I wouldn't say it applies every single time either. There's too many variables. Sometimes a rewrite is just a rewrite. Sometimes the level of bloat or feature-creep is tiny. Sometimes the old code was so bad that the rewrite fully offsets any bloat.
The second system effect isn't that a rewrite necessarily has more bugs/problems. The second system effect is that a follow-on project with all of everybody's dreamed-of bells and whistles that everybody in marketing wants is going to have more problems/bugs, and may not even be finishable at all.
A natural follow-up to your question might be: "If everything is expanding, then wouldn't the ruler itself be expanding, so the expansion becomes unobservable?"
I'm not a physicist, but from my understanding, the situation is a bit more complicated than the phrasing in your question suggests.
Observation #1: The light from far-away galaxies is redshifted (spectral lines are a bit off from where we'd expect them to be). This suggests that these galaxies are moving away from us. The farther away the galaxy, the more it is redshifted. This suggests that the farther away the galaxy, the faster it is moving. Observations indicate that the recession speed is directly proportional to distance.
This observation is consistent with general relativity, which suggests an expanding universe with homogeneous mass.
But on a smaller scale, gravitational binding somehow takes over, and on even smaller scale, things like electromagnetic and nuclear interactions start having a greater impact, and that's why the Milky Way isn't itself expanding. For that matter, even Andromeda (0.8 Mpc) is too close to be affected by Hubble-style expansion, which only becomes observable at the multi-megaparsec scale.
The Indian Supreme Court introduced the Basic Structure Doctrine in 1970, allowing the judiciary to overrule constitutional amendments if they are found to contradict the "basic structure" of the constitution.
It's original purpose, if I understand correctly, was to guarantee that fundamental rights were an essential part of the constitution and couldn't be amended away.
Wikipedia says that multiple countries appear to have adopted the principle: Pakistan, India, Bangladesh and Uganda.
It's also because making some of these decisions (choosing health insurance, deciding how much to save, etc.) involve two considerations---the first being purely analytic (mundane cost vs. probability of contracting major disease vs. cost of catastrophe) and the other being necessarily extra-analytic (how risk averse the individual is).
One can objectively reason through the first set of considerations, while the second involves a subjective element and is likely heavily influenced by their upbringing and life experiences.
Nobody knows how much to save or how much to spend on insurance. It's completely reasonable to seek advice, and one's parents might be a great starting point.
Instead of the ones(10^0)-thousands(10^3)-millions(10^6)-billions(10^9)-... system followed in most other parts of the world, the Indian numbering system uses ones(10^0)-thousands(10^3)-lakhs(10^5)-crores(10^7)-...
So, for example, half a million subscribers (500,000) would translate to 5 lakh subscribers (5,00,000).
If you ignore syntax and pretend that the following is a snippet of Java code, you can declare that a variable x always holds an int, like so:
var x: int = y + 5
Here x is the variable being defined, it is declared to hold values of type int, and its initial value is given by the term y + 5.
In many mainstream languages, types and terms live in distinct universes. One starts by asking whether types and terms are all that different. The first step in this direction of inquiry is what are called refinement types. With our imaginary syntax, you can write something like:
val x: { int | _ >= 0 } = y + 5
Once again, x is the variable being defined, it is declared to always hold a value of type int at all relevant instants in all executions, and that its initial value is given by the term y + 5. But we additionally promise that x will always hold a non-negative value, _ >= 0. For this to typecheck, the typechecker must somehow also confirm that y + 5 >= 0.
But anyway, we have added terms to the previously boring world of types. This allows you to do many things, like so:
val x: int = ...
val y: int = ...
val z: { int | _ >= x && _ >= y } = if x >= y then x else y
We not only declare that z is an integer, but also that it always holds a value that exceeds both x and y.
You asked for the type of a function that multiplies two numbers. The type would look weird, so let me show you an imaginary example of the type of a function that computes the maximum:
val f : (x : int) -> (y : int) -> { int | _ >= x && _ >= y } = ...
This doesn't really get you to the maximum, because f might be computing max(x, y) + 5, but it does show the idea.
The final step in this direction is what are called full-blown dependent types, where the line between types and terms is completely erased.
Or at least not completely extinct in South India. Some of my favorite childhood memories are from these messes (short for mess hall, I assume). You go there, pay what they ask, eat what they serve.
MTR, Brindavan on MG Road (though that's long gone), Iyer Mess in Malleshwaram.
What they lack in choice they usually make up for in taste.
You're right that they have a more traditional ambience and newer restaurants offer more choice, but they are definitely thriving in the parts of Bangalore that I grew up in.
Yeah sorry I intended there to be a more clear constraint on the claim I was making. It's mostly extinct in the anglosphere, so english doesn't really differentiate. But the concept itself is still popular globally.
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.