this post was submitted on 23 Feb 2025
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This sort of comic always bugs me. Observation in QM is not the same as observation in layman terms.
Best think of it as hit it and watch the pieces fly. When you get small enough, you can't approximate out the impacts. It's akin to studying road traffic by sending an overloaded freight truck the wrong way and counting tires that hit the verge. It might also affect the current traffic's motion.
This is something that I noticed is hard to understand to most people. My SO got served a video of the double slit experiment and thought it was like magic, until I tried to explain to him that at this scale, "observing" doesn't just mean looking at it. Observation makes you part of the system and causes the system to change.
That is part of what bugs me.
Quantum mechanics isn't magical or unknowable. It's just an area of physics where some of our base assumptions/approximations break down. It's not even that hard to wrap your head around, it just seems most people don't want to try.
Magic is just stuff we don't know but don't care to know :)
No, it's not. Magic isn't real.
Quantum mechanics is an area of physics that leans on measurement as a central concept. What things are doing between measurements is not its' concern, and don't even stop and think about it, you'll go nuts, just shut up and calculate!
There is a magic to perception nothing else can replicate. I'm pretty sure awareness is existence, so it's attention has to change reality.
Perception and observation are different things. Air molecules can be "observers" when looking at electrons etc.
I think we need to build a time machine to go back to Atlantis, to kill Ramtha and make sure that What the Bleep? never gets made.
"Observation" in a QM sense has nothing to do with sapience of anything like that. It literally just means that something needed the information and it collapses the waveform. It's any time it influences another particle. It doesn't matter what that particle is. If it needs to know the state or the particle we care about then it "observed" it. Humans or animals need not be involved.
Tbh, I think no one who hasn’t solved the Schrödinger equation at least once (at least time independent), should be allowed to talk about quantum.
Like, the uncertainty principle is really really fucking cool when you understand why it works mathematically. But without differential equations and linear algebra, I don’t think it’s possible to really conceptualize what’s going on in quantum.
Idk, I always try to explain to students the deficiencies of the Bohr model and explain the significance of the electron cloud, but probability is hard.
One of my favorite things in quantum was deriving the “quantum numbers” they have you memorize in chemistry (if you don’t remember, you probably got a SPeeDy F) It’s beautiful to watch the way they emerge from the second order diff eq.
I don't think solving the Schrodinger equation really gives you a good idea of why quantum mechanics is even interesting. You also shouldstudy very specific applications of it where it yields counterintuitive outcomes to see why it is interesting, such as in the GHZ experiment.
While I'm rusty as hell, my physics degree was actually focused quite a lot into QM.
It's perfectly possible to get a reasonable understanding of what's going on without going head first into the maths. There are definitely areas however that we don't have a good conceptual model of yet. For those, the maths definitely leads the way. 90% of QM is comprehendible with relatively little maths. You only need the maths when you start to get predictive.
I don’t think you can get the intuitive feel/the “why” without the maths.
I guess I get frustrated when I have to teach algebra based introductory physics for similar reasons - everything makes so much more sense when you understand how the pieces fit together. (Why make them memorize d=d0+v0t+1/2at^2 when all that is integrating a constant twice? That you can set v=0 to find the time of maximum height, because you’re using a derivative to find a max! And then that helps you get why it works, and then even how to possibly explore non constant acceleration!)
I got really fucked over because I didn’t take linear (at all - advising in my physics department was non existent which lead to things like taking classical before Diff Eq lol) and so things like eigenvalues - which tbh I think is kinda the money shot - that things end up quantized and discrete - that took a while for me to get what that meant.
I find QM quite confusing, in that one can observe only the eigenvalues and not the state itself. Why is it specifically, or is this wrong conceptualization? Also, how does particle-ness relate to the eigenvalues?
Eigenvalues come from linear algebra. I think a difficult think in general with understanding them is often the failure of most middle/high school math teachers to teach matrix operations at all. (I’m guessing because matrix multiplication never shows up on SAT/ACT). Here’s a good explanation for the math on finding eigenvalues and eigenvectors.
But basically eigenvalues are going to be associated with certain matrixes/vectors. You take a “Hamiltonian” of a system, which is a way of describing possible energy values in the system, and it’ll give you a set of possible answers - pairs of eigenvalues and eigenvectors that describe the system.
In effect - you get things like the quantum numbers. That the 1st energy level has 1 subshell can hold 2 electrons, both with opposing spins. That the 2nd energy level has a 2s subshell that holds two, that 2p holds six. You get your n (1st energy level, 2nd so on as you go down periods of the periodic table), l (subshell - don’t get a SPeeDy F), m (which breaks down where in the subshell they are) and the need for opposing spins.
Thank you for in-depth explanation! Though I already know the eigenvalues and eigenvectors, as a math major. What I am curious of is: why can't we only observe e.g. energy values? I heard that one can only observe commutative operators or something, but honestly why is quite unclear.
I’ll try to dig out Griffith for a better explanation but has to do with the fact that when you do a partial derivative you kinda lose information I guess?
(Idk, this is heady trying to make math into reality shit and I got a “c” in the class (for reasons partially related to other things) - also, there might be a way to do latex in markdown but I’m a bit too stoned to figure out, look up Schrödinger equation on wiki for maybe a helpful visual aid)
So go back how often we do implicit differential because it’s just an opportunity to look at how sexy the chain rule [edit: product rule, you get me though. math is easier sober] is. d(xy)/dx = xy’+x’y god fucking dammit that gorgeous
But okay. Think about position and velocity. Velocity is the derivative of position right (and also connected to energy - KE = 1/2mv^2 and E = mc^2 lol)
But since velocity is a derivative of position, it loses information. d(mx+b)/dx turns into m, no way to ever get b back with an initial value condition.
Then - omigod, when you take a partial - you have to ignore dependence. curlyd(xy+by)/curlydx turns into y and then things is really fucked if there was any dependence on y (ie, doing curlyd(xy+by)/curlydy would give you a different answer if you did that first order matters I guess)
There are some operators that are just exclusionary. Once you chose to look for one, you’ve discounted the chance of finding the other. Taking position versus taking energy/velocity. And then the fucky thing there is lots of shits mass is measured in eV/c^2
(I’m neglecting a proper discussion of momentum which is 100% where someone can come in and humiliate me. Please do so.)
You're right. But the thing that's interesting about the double slit experiment though is that it works on only a single photon. It's as if all the traffic was created by a single car. So classically you might not think that the single car should care if the freight truck is heading down a different lane than the car but in QM it does, because the car is in a superposition of occupying several lanes.
I'm probably driving the analogy straight into the ground of course
Which is what's so "magical" about it - Newtonian rules seem to break down at the quantum level.
It was an incredible discovery, and for practically anyone not a physicist, it's incredibly hard to comprehend. I say this as a not-a-physicist who struggled to comprehend it decades ago, and read several books on the subject to finally get my head around it (as much as a non-physicist can).
Also, it's just a meme mate.
I disagree with it being hard to comprehend. The maths is an absolute bitch, but the basic premise is fairly simple. Everything is (quantised) waves. The rest clicks, once you get your brain to accept this. Everything else is a consequence. Those consequences can lead you down deep dark tunnels, filled with evil maths and mind bending results, but the basic idea is simple.
I have a bit of an issue with memes that are actively misleading.
Well, famously, they're waves and particles. The double slit which way experiment will only set off the detector in one slit, as if it was a particle. Yet, without a detector it will interfere with itself as if it were a wave that passed through both slits.
QM entities are quantised waves. You can make a wave look very close to a particle quite easily, a particle can never behave like a wave.
Dumping the mental short hand of particle interactions is one of the main reasons most people can't get their heads around it.
That’s wrong though, and further belies my point about math, and perhaps needing to take a quantum class before talking about it.
They are particles and waves.
What is a particle, what is a wave? QM entities are neither. They are a 3rd thing. A quantised wave is the term my university professor used as a short hand. The nature of that wave is described by the Schroeder equation + its constraints. Certain interactions will bound it heavily, and so make it look particle like, others emphasise the wavelike properties.
You require the maths to actually do anything useful with it, but not to get the basic concepts. It's no different to the rest of physics, in that. E.g. you can understand the concepts of orbital mechanics, without being able to calculate them.
psssst, it's just a meme
Lots of folks get their superficial education from memes and will be mislead by this...
well that's their own fault, and it's not like stuff like this is vital information for the average person
So why are you so upset with us trying to fix it?
I personally find the anti science, anti learning crowd has gone from amusing, to annoying, to terrifying.
I'm not upset
Calmly arguing for misinformation and anti-science rhetoric isn't better.
i wasn't, i was merely pointing out that this is a meme meant as a joke and not meant to be educational
Specifically, because it's non-vital information for the average person, I really do not think you can blame anyone for merely learning about it through memes. But I do also think this problem is much greater than just memes. I did not receive a better explanation during high school, despite opting for more advanced physics classes and us repeatedly telling our teacher that it makes no sense to us. I have to assume that our teacher did not know either. As such, I got the impression that more advanced physics is just devoid of any actual logic, which was a major factor why I decided against pursuing it further in college. Reading a proper explanation under a stupid meme, could've made the difference for me.
sorry I was in the assumption that most people know that it was simply a joke and it doesn't actually work like this
The teacher very likely didn’t understand either.
Physics isn’t considered an important enough subject to hire qualified teachers for. My state substantially simplified our physics qualifying test recently because it was “too hard” - and already it solely covered CM.
This will also factor into how they treat you as a teacher - you aren’t essential, you’re kind of weird and sometimes you annoy the math teachers by begging them to shut up about “cross multiplying.” I guess some states see physics as a “core” science - but where I am I can think of two high schools in a two hour radius that even offer intro physics.
In general, most of the people who sat in QM with me were able to find substantially better paying careers than I did. If you pursue mathematics beyond calculus, then usually you are qualified for jobs that will either pay you a fair wage or at least treat you better than teaching does.
So was "Donald Trump for president" and look at the damage that has caused.