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A collection of some classic Lemmy memes for your enjoyment
Whenever any of this comes up I remember that physics professor's speech on first day of quantum mechanics that got viral:
“Nobody understands quantum mechanics. The people who came up with it don't understand it. I will do my best so that by the end of this course you don't understand it either, and so you can got out to the world and spread our ignorance.”
Or something to that effect.
I'm so good at not understanding stuff. My time has come.
Quantum mechanics is illogical and stuff that happens makes no sense but can be recrcreated through experimentation....as long as you don't look at it.
The end
Quantum mechanics is extremely logical - we understand the math extremely well, and the math describes reality better than any other theory.
It is, however, not intuitive.
I was just being cheeky
I'd say we understand quantum mechanics better than most things.
We know more about the behaviour of an electron than we know about the oceans, the Earth, the sun, the weather, the stock market, the human body, prime numbers, and so on.
We generally have a grasp of "why" for that stuff though, even if the whole picture is currently hidden or too complex.
Do you mean "why" as in "why did X cause Y" or as in "why are things the way they are"?
In the former case, quantum mechanics is our most precise theory for coupling causes and effects, predicting the outcome of experiments to an incredible degree.
In the latter case, do we really have a grasp of that for anything? Why is the gravitational constant the value that it is? Why is pi the ratio of a circle's circumference and it's diameter? Mostly we ultimately have to say that it is so because we can observe that it is so. For quantum mechanics it is the same.
Or do you mean "why" in some other way?
We understand the "how" better than most things. Quantum mechanics is extremely well-supported mathematically and experimentally. I think that's what they mean. The "why", an understanding of what a system that generated those results looks like at a macro level, basically no clue.
The consensus seems to be that the math works, don't try to figure out why.
Whenever this picture comes up I remember that it's wrong - both electrons on it have the same spin, one is just rotated 180°, but it says +½ for one and -½ for the other, is like a part of the joke?
All electrons have spin 1/2, that's a property of it being an electron. They have a spin vector (the arrow shown) and whether it is in the same direction or opposite direction to the magnetic field it's in determines where it is plus or minus.
Now you might think "but what if it is not entirely aligned with the field, then it wouldn't be 1/2", which is true, on aggregate for large numbers of electrons, but if you ever look at a single electron its spin will either be "up" or "down" never any other orientation.
This is the kind of thing people are referring to when they say "no one understands QM", we know it is the case, we can measure it and predict it, but it makes no fucking sense.
Imagine a mathematical concept that approximates a particle across a spherical plane. Now imagine a force emitted from this sphere in a field. Okay, we're ready to talk about why this is wrong, too.
There's no analogy for any of this that doesn't have some flaw.
All analogies have flaws. If they didn't, they wouldn't be an analogy, they would be describing the very thing itself.
One of my favourite things is the one-paragraph short story "On Exactitude in Science":
On Exactitude in Science Jorge Luis Borges, Collected Fictions, translated by Andrew Hurley.
" …In that Empire, the Art of Cartography attained such Perfection that the map of a single Province occupied the entirety of a City, and the map of the Empire, the entirety of a Province. In time, those Unconscionable Maps no longer satisfied, and the Cartographers Guilds struck a Map of the Empire whose size was that of the Empire, and which coincided point for point with it. The following Generations, who were not so fond of the Study of Cartography as their Forebears had been, saw that that vast Map was Useless, and not without some Pitilessness was it, that they delivered it up to the Inclemencies of Sun and Winters. In the Deserts of the West, still today, there are Tattered Ruins of that Map, inhabited by Animals and Beggars; in all the Land there is no other Relic of the Disciplines of Geography."
Source: https://www.sccs.swarthmore.edu/users/08/bblonder/phys120/docs/borges.pdf
Something something map territory
You lost me at 'spherical plane'
A hollow sphere.
You could picture this as a spherical cow of uniform density if you prefer.
I recall a Richard Feynman video where the interviewer asks him to explain how magnets work.
His answer amounts to "I can't explain that to you because if I gave you an accurate answer it would be too technical for it to make sense to you, and if I simplified it to the extent that you could understand, it would no longer be a meaningful answer."
His point was that we don't understand the interaction between fundamental forces enough to say, if we were to try and answer the question accurately enough.
So, in one sense ICP was right that we don't know how magnets work. But also they were wrong that scientists be lying. They shouldn't have been pissed.
That interview answer always seemed like a cop-out to me. You could make a comparison to gravity to explain how magnetism "just is".
I expect Feynman’s answer, if he had a whiteboard and unlimited time, would’ve been to dive into Maxwell’s equations.
With that in mind, his answer makes complete sense. Good luck explaining coupled PDEs to people who aren’t mathy in a few sentences without visual aid. The analogy to the gravitational force isn’t on point; there’s a lot more to be said about how magnets tie to into E&M more broadly, compared to gravity.
Though you’re absolutely right that once you get deep enough into any topic in physics that the answer to “why?” inevitably becomes “it just be like that”.
The analogy to the gravitational force isn’t on point; there’s a lot more to be said about how magnets tie to into E&M more broadly, compared to gravity.
Yeah, a proper answer would need to dive into how it relates to electricity for sure
Title-Text: "Of these four forces, there's one we don't really understand." "Is it the weak force or the strong--" "It's gravity."
Sounds like a class with an attribute called spin.
It does however also have repercussions that are inline with it being a sphere that is spinning.
There was great episode on PBS space time about it.
https://www.youtube.com/watch?v=pWlk1gLkF2Y
In short it doesn't rotate, it just has magnetic field that behaves as if the source was spinning charge
The electron is rotating in the sense that it resists a tilting force.
https://www.youtube.com/watch?v=PdN1mweN2ds
Disclaimer: My knowledge of physics ends at the high school level.
Apparently there is an experiment where they get an object suspended in water to rotate when being bombarded by electrons with the same spin.
Although my physics knowledge is probably less than the average highschool level.
I studied (a single course...) at university level and I think you understood at least as much as I did.
Right-hand rule bitches!
Yeah, "spin" was a stupid thing to call it. We have a nice, hard definition of what "spin" is on a macro scale. Why take a complex property of matter that we don't have a name for, and give it the same name as a fairly common, easy-to-understand phenomenon? Extraordinarily smart people being idiots, honestly.
Imagine a woman in hot pants with thighs like a Robert Crumb dream woman.
I don't know if it helps with this problem though.
A ball, however tiny, has 3 dimensions, it has a surface that moves around a mathematical point at the center of the sphere.
A point of zero dimensions has no diameter nor perimeter, no surface with which to spin. Yet when influenced by a magnetic field, a point-like indivisible particle behaves as if it does spin.
As Chief Brody might say, we're gonna need a bigger math!
How about imaginary numbers and the complex plane?
Now add the Uncertainty Principle, just for shits 'n' giggles!
Probability space! Probability amplitudes and polarizations!
It's only half spinning too.
The way I understood it (probably wrong): imagine if a point like thing, but is actually a wave, hits something else. It will leave a trace on the detector curving in a certain direction. This is interpreted as angular momentum aka spin.
There are also things like Hydrogen Fine Structure , that behaves as though it is a ball that actually spins. 🤷
Ah yes the spin
I've always understood it more like a cake that's moist, but it's not a cake and it's not moist.
