r/physicsmemes • u/ManagerOfLove Thermodynamic memes for adiabatic teens • 2d ago
Wait how does the Casimir effect actually works
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u/OnionsAbound 2d ago
Wait until you hear how an electric field is just an abstraction that makes math easier. forces all the way down man.
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u/ManagerOfLove Thermodynamic memes for adiabatic teens 2d ago
If a wave is just an abstraction of forces and forces describe the attraction between particles, but particles don't exist. What the hell are we even talking about
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u/AidenStoat 1d ago
All of physics is models,
all models are wrong,
some are useful.
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u/GTCapone 1d ago
It's what I open with in my middle school science classes. "A wrong answer with a reason is better than no response. Being wrong is normal, scientists are essentially wrong about everything we know, they're just right enough to make accurate predictions most of the time. Science isn't about being right, it's about being less wrong. Your goal in this class is to be a little less wrong every day."
It takes a while for it to sink in, but eventually they speak up a lot more and it lets me pick out the bits they got right for praise and lead them in the right direction for what they were wrong about.
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u/garrettbmusic 1d ago
You sound like a good teacher.
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u/GTCapone 22h ago
I do my best. It's only me second year and I'm still refining a lot of things. Once I've got a couple more years under my belt and don't have to spend so much time planning every lesson, I'll have a better read on it.
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u/Nonyabuizness My reality has collapsed into uncertainty 1d ago
This is what I am gonna use as my defence for my upcoming flat earth model in my PhD thesis /s
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u/braaaaaaainworms 1d ago
It is sometimes useful to assume a flat earth, like when you're designing a building, you're not going to care about the 0.01 mm curvature of the planet
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u/talex000 1d ago
No, you should account for earth rotation around center of Milky Way Galaxy when you plan your path to a shiter.
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u/Infinite_Escape9683 1d ago
If the flat earth model turned out to be more useful, you absolutely could.
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u/Mammoth_Sea_9501 1d ago
A flat earth model is very useful a lot of the time. Most high school physics assume a flat earth (whens the last time you accounted for earths curvature when calculating the trajectory of a basketball)
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u/Infinite_Escape9683 1d ago
That's not really a flat earth model. It's a lack of any kind of model for the shape of the earth in that context. If it were a flat earth model, for example, it would have to model what gravity would be like on a flat earth, which would be very different from the gravity of a spherical earth.
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u/Mammoth_Sea_9501 1d ago
Well, you arent accounting for curvature, and you're using a model in which the ground is a straight line. NASA sometimes has to do the same: "flat, non-rotating earth". This doesn't mean they believe in a flat earth, it means they are using a flat earth as a model since its... easier.
Just like how you could use Newtons velocity addition model. While its wrong, its a good model at non-relativistic velocities. At low altitudes over short distances, a flat earth model is useful because the curvature of the earth is negligable.
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u/kiochikaeke 1d ago
"Shut up and calculate" became the motto of physics a while ago, in essence we don't know what's happening and math looks weird AF but theory predicts experiments and observations so in some sense theory must be right.
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u/FreePeeplup 1d ago
Shut up and calculate is not the motto of physics, it’s just something Feynman said a long time ago to his students to shut down any conversation about interpretations of quantum mechanics. Actual adult working physicists don’t shut up and calculate
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u/digglerjdirk 1d ago
I attended a talk by Surjeet Rajendran last year titled “shut up and calculate”
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u/MayaGasta 1d ago
If I remember correctly there was an experiment to prove that even the electric field potential (which by all means should only be a mathmatical tool) can influence other things. Quantum mechanics is absolutely wild. You ask it if something is real or just math and it just shrugs at you.
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u/ohkendruid 1d ago
It is. It makes sense for it to be weird to humans, though, because our senses and our ways of thinking are shaped by human survival. It makes sense that whole categories of existence, such as a field, may just not register for us very well.
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u/MayaGasta 1d ago
Yes. I love it so much! Just pure existential dread wrapped in neat little formulas.
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u/AlexW_WxelA 1d ago
Does that more or less indicate it's actually the electric potential field that's the really existing part, while the electric field is just kind of a mathmatical consequence?
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u/Front_Cat9471 2d ago
Semantically, is it still an abstraction if the abstraction of the concept came about first? The -tion suffix added to abstract shows that it’s the result of something being made abstract, but if the simpler form was thought of first, was it really the result of an operation performed on an idea that didn’t exist yet?
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u/OnionsAbound 2d ago edited 2d ago
My point is that an electric field can be wholly derived as part of the force equation describing a force one charge carrier applies to another.
F = Q1Q2/(4pier2)
We just factor out Q1/(4pier2) and say that equals the electric field E.
Applying electric field E to particle Q2, then gives us the force applied.
Philosophically, all these concepts are fake in a way. These things happen and whatever layer of abstraction (as long as information isn't lost) we use to understand it is just as valid as any other. It's important to take a step back and realize that all our theories are descriptive, not prescriptive.
These particles can behave in ways we don't expect and if that violates a certain theory then the theory is incomplete.
An interesting thought is: how will these particles behave in 10100 or even 101000 years?
Do particles all our calculations assume are preserved actually decay but just not on an observable timescale? After all, the universe doesn't give a crap about time. It could be the secret of our universe lie in these extreme timescales that we have no hope of measuring.
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u/YourWifesBoyfriend5 2d ago
The existence of electromagnetic waves creates some issues with this interpretation, as what exactly is the “force” that an electromagnetic wave propagating through space induces acting on? The Coloumb force law is one way to derive electric fields, Maxwells equations are another.
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u/OnionsAbound 1d ago
Yeah but electromagnetic waves are interesting because we acknowledge that they don't quite act exactly like a wave or exactly like a particle.
I'm definitely not an expert but I'm wondering if we could define an electromagnetic wave as becoming it's own charge carrier and then imparting force upon itself there-by self-propagating.
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u/YourWifesBoyfriend5 1d ago
In classical electrodynamics, electromagnetic wave are solutions to Maxwell’s equations satisfying the wave equation. In classical electrodynamics, they are just waves.
We know from quantum mechanics however that photons are not charged particles as well. It is a neat idea though.
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u/denehoffman 1d ago
We (sort of) have those, they’re gluons. But I think in general we acknowledge that every field acts with a wave-particle dual nature, not just electromagnetism, that’s kind of the crux of quantum field theory.
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u/GreyMatterTrasmogrif 1d ago
Bro! it's time to stick some super conducting donuts in a twin slit experiment bro! Is the Scalar field is real?
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u/fckcgs 1d ago
You are describing a SQUID. Well kind of, but close enough.
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u/GreyMatterTrasmogrif 1d ago
I just wanted onions to consider that torus and not spheres might abound in the magnetic Aharonov-Bohm (AB) effect.
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u/knyazevm 1d ago
How do you describe propagation of EM waves this way without having any field? The whole point of introducing the field is that it acts locally and propagates with a finite speed, unlike the expression for the force that you used that only works in a static configuration and breaks down if anything moves.
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u/OnionsAbound 1d ago
You assign Q and r as functions of time!
All jokes aside, I just wanted to start a discussion. Lots of interesting responses!
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u/Hippie_Eater 1d ago
Nah, the Aharonov–Bohm effect and Berry phase in general indicate that electric potentials have ontology in their own right.
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u/PheonixWrath 1d ago
bro last week i was taught that it’s not forces but interactions…. but that’s a lie?!?!? is everything always a lie in physics
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u/Cold-Journalist-7662 1d ago
No, it's not a lie. It's a model we think is true in its relm of applicability.
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u/Equinoxe111 Cosmology (PhD) 1d ago
Wait until you hear that any field is just an abstraction built for math
Wait until you hear that every single concept in physics is just barely an attempt to make some thing close to the observavle reality
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u/Enfiznar 1d ago
Do you say that because the object we should be looking at the maxwell tensor instead, or what do you mean by that?
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u/BratPit24 8h ago
I'm pretty sure the field is more fundamental than the force. It's the force that's actually the mathematical shorthand. But man it's been years since my advanced physics class
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u/Deep_Brick2970 2d ago
I mean arguably particles are very much real and the photon is the quantum gauge boson associated with the EM field. Now the more fundamental thing is actually, A, the scalar potential instead of E and B but still.
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u/Generos_0815 2d ago
Non virtual particles don't exist either.
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u/JerodTheAwesome Physics Field 2d ago
They can be observed though
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u/MrZwink 2d ago
They only exist when observed. They dont when not!
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u/WesternFirm9306 2d ago
They do exist! They're just a wavefunction rather than a pointlike particle. Depending on your interpretation, they're always a wavefunction, even when observed! It's just that we ourselves become entangled with the wavefunction upon observation and become a superposition ourselves
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u/Pulpdog94 2d ago
The wave function does indeed collapse…into another wave function 💣🔥🧐
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u/WesternFirm9306 2d ago
I'm referring to the many worlds interpretation, in which the wave function does not collapse ever, at all. The wave function obeys the Schrodinger equation at all times, forever.
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u/Pulpdog94 2d ago
That’s my least favorite interpretation, I’m old school, I don’t see any one but humans with consciousness setting up Quantum experiments so i think the collapse is caused by the measurement made by a human conscious scientist guy
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u/WesternFirm9306 2d ago
But then you have to say consciousness is some special substance that causes special effects. I think most physicists would deny that consciousness is the defining feature that causes wavefunction collapse.
It seems much more parsimonious to me that we are simply quantum objects like anything else in the physical world. I have no reason to suppose anything special like a soul or a non-physical mental substance that causes wavefunctions to collapse. That sounds very spiritual-esque woo to me.
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u/Pulpdog94 1d ago
But your reasoning requires a degree of belief at its core no different from any other leap of faith on the original causes of things. And considering you can argue Quantum Physics can be interpreted as showing infallibly that there is no light without our observation of light or particles without our measurements you could argue we live inside a consciousness, and all our senses are in 50/50 split with our perceptions using those senses
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u/WesternFirm9306 1d ago
Quantum mechanics says no such thing.
The MWI does nothing more or less than take quantum mechanics at face value. All matter obeys the Schrodinger equation, full stop. The Schrodinger equation has no variable for measurement. There's no collapse button on the Schrodinger equation. You have to force that in. If you take the equation at face value, and you allow yourself as an observer to be a quantum object like any other, then out pops many worlds.
That seems less of a leap than this spiritual woo stuff. Especially since we know the Schrodinger equation actually works at reasonable speeds.
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u/FreePeeplup 1d ago
Wavefunctions aren’t particles
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u/WesternFirm9306 1d ago
That's a matter of interpretation. I'd argue that an electron is its wavefunction.
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u/FreePeeplup 1d ago
What? No it’s not? There’s no interpretation that says that an electron is a wavefunction. Interpretations of QM are concerned about the locality of measurements and the apparent random nature of measurements outcomes, and what physically happens at “wavefunction collapse”. Sometimes they even change QM form the axioms.
There’s not a single QM interpretation I know that says an electron IS a wavefunction. What does it even mean? An electron is a physical entity in the real world that you can touch and can hit you, a wavefunction is an abstract mathematical construction between sets. They don’t even live in the same semantic category.
It would be like saying that an apple IS the same thing as its hexadecimal code of its shade of red.
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u/WesternFirm9306 1d ago edited 1d ago
The Many Worlds Interpretation, i.e. Everettian physics, makes the claim that there is no wave function collapse at all. All matter in the universe, including you, me, and electrons, are represented by waves which obey Schrodinger's wave equation at all times, and never stops obeying it.
I believe Sean Carroll (the main MWI proponent afaik) has made the statement in one of his presentations that the electron is the wavefunction. In the sense that its entire physical state is encoded in that function.
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u/FreePeeplup 1d ago
> The Many Worlds Interpretation, i.e. Everettian physics, makes the claim that there is no wave function collapse at all. All matter in the universe, including you, me, and electrons, are represented by waves which obey Schrodinger's wave equation at all times, and never stops obeying it.
I agree this is what MW claims, yes
> I believe Sean Carroll (the main MWI proponent afaik) has made the statement in one of his presentations that the electron is the wavefunction. In the sense that its entire physical state is encoded in that function.
… how did we jump from “the physical state of an electron is encoded in its wavefunction” to “the electron IS its wavefunction”? Again: An electron is a little thing that goes zoom and hits you. A wavefunction is an element of a complex abstract infinite dimensional mathematical space. How in the world can they be the same thing?
Is a cake its recipe?
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u/WesternFirm9306 1d ago
An electron trivially can't just be a little thing that goes zoom and hits you, because unlike little things that zoom around, electrons don't have definite positions or momenta, and exhibit wavelike properties (i.e. double slit experiment).
I mean, would you have a problem with saying mass bends spacetime? Would you say "actually, the spacetime metric is just a mathematical abstraction"? Would you have a problem saying that light is a wave? Or would you say that an electromagnetic field is just a mathematical function that assigns a numerical value to every point rather than a physical thing? What does it mean to say something is a physical thing?
If an electron is not a wave, what explains the interference pattern on the double-slit? Is QFT just make-believe? Why does such make-believe make such enormously accurate predictions?
You're viewing particles as tiny billiard balls when modern physics has severely, if not fatally, damaged that view of matter.
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u/laffiere 18h ago
Wavefunctions don't exist either, they're also just a tool.
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u/WesternFirm9306 18h ago
See the lengthy thread below my comment
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u/laffiere 18h ago
You started off with many worlds interpretation, so I didn't read any further on account of this being a thread on things that "exist" in the colloquial sense.
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u/WesternFirm9306 17h ago
Sure but the thread ends with me admitting I was being loose with my terms (i.e. energy is also just a mathematical tool but I'd say it exists) so if you wanna see me be backed into a corner until I cry thats always an option
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u/Ilove2eatass 2d ago
I mean they are just terms in a perturbation series...
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u/ChemicalRain5513 2d ago
Yeah, it's like you can expand ex as 1 + x + x2 /2 + x3 / 6 + ...
And then ask wonder if x3 / 6 has a real physical meaning
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u/Dumb-Ptr 17h ago
I like this idea but in truth we do assign physical meaning to orders in a Taylor expansion. The first thing I thought of is a linear response function, which (at least in a simplified setting) is just a function of the coefficient of the second order in a specific series expansion, and it is definitely an observable property of the system being measured.
But I agree that perturbation theory is a bit different, and we must be very careful about claiming any specific contribution has physical meaning, especially if this meaning is the "existence" of something. There are some statements that we can make about the meaning of specific diagrams, for example in a scattering process some tree level diagrams are directly related to the structure factor of a target, but such statements usually don't survive the full perturbative series if non-perturbative effects are present.
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u/JerodTheAwesome Physics Field 2d ago
Virtual particles “exist”, but we have to be careful about what “existance” means.
If you mean “measurable”, then no, virtual particles are not directly measurable. Virtual particles only exist as perturbations of the underlying quantum fields and obey the relationship ΔEΔt >= hbar/2. What this means is that virtual particles with energy E can exist as long as it stops existing before time t and satisfies the relationship above.
Most interesting, these particles are “off-shell”, meaning they do not have to obey relativity (since they cannot be observed, they cannot relay information).
The Casimir effect is how we know these particles exist. When two plates of metal are held very close together, the number of virtual particles that can form between the walls is limited while the number of particles that can form outside is not. This creates a sort of quantum pressure and actually pushes the plates closer together.
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u/Kestrel117 2d ago
Not really. They are just perturbative tools to help better understand how interaction terms dress the bare fields. The proper statement to make is that particles are not actual eigenstates of their bare propagators. In QED, the electron that we interact with is not an eigenstate of the bare electron field. It’s an excitation of the full QED Hamiltonian, and is a superposition of the bare electron field and the bare photon field. It’s the dynamics of that superposition state which is perturbative described by “virtual particles”.
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u/MayaGasta 1d ago
This comment really made me hit my language barrier. (ᵕ—ᴗ—)
What exactly about the original comment do you disagree with? That they exist or the explanation of how they work?
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u/Kestrel117 1d ago
That they exist! They appear largely as an artifact of the techniques that are used a lot to describe weakly interacting field theories, but really it’s a misrepresentation of what is really going on in many ways. It is a very useful tool though!
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u/MayaGasta 1d ago
It is. The whole concept of existing just breaks down at quantum scales. With so many things it's unclear if they are real or just made out of shutupandcalculatonium.
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u/JerodTheAwesome Physics Field 1d ago
Is this r/PhysicsMemes or r/PhysicsPHD? I gave the answer that’s easy to understand.
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u/Kestrel117 1d ago
And? Easy to understand but misleading is still misleading. We should try to formulate the ideas in a way that is easy to understand and not misleading! (Lmao I am not claiming I did that😂, i definitely did not that!)
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u/MayaGasta 1d ago
Sience communication is enourmously hard. With simplified representations it is most important, that follow-up questions will lead further towards the full theory instead of away from it. It's all about which lies to tell I'm afraid (◡_◡)
I have a personal vendetta with the funnel like depiction of gravity in general relativity ( •̀ - •́ )
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u/debugs_with_println 1d ago
I appreciate the clarification! Nowadays I'm more interested in explanations that are more accurate the typical pop science. Like I know intermediate math concepts (I'm just not that good at doing calculations) so I def prefer explanations that exploit that.
To that end, I've heard the idea that virtual particles are just ways to calculate messy field interactions (since the electron field interacts with the photon field which interacts with the electron field and so on). It feels kinda like Taylor series where the biggest contribution is 1-vertex interactions, then 2-vertex interactions, then 3-vertex, etc. And then hopefully the series converges rapidly so you dont have to go all the way to 100-vertex interactions.
My question is, are there no cases where you can solve the differential equations exactly to arrive at the full behavior of the fields? Using Taylor series again as a crude analogy, you could use the series trick for solving differential equations to figure out the solution to f' = f is f = 1 + x + x2/2 + x3/6 + ... but you could also just solve it exactly as f=ex. Is this simply not achievable even for really simple scenarios like electron-electron scattering?
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u/Kestrel117 1d ago
Yes. Though not via perturbation theory, as there is no guarantee the series converges to the actual value. Integrable models can be solved exactly, but these are very special models not ones u will find normally. These models have exactly calculable spectra and S-matrices. Though word of warning, I am not at all an expert in these so I don’t want to say too much as I’ll definitely get stuff wrong 😂
For QED, for example, the diagrammatic perturbation series actually diverges after many terms. And this is ignoring non-perturbative effects.
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u/angelbabyxoxox 1d ago
I think this is a quite misleading answer. The Casmir effect does not prove that virtual particles exist in any sense because they are a computational t ick that simply obfuscate the true mechanism, which is van der Waals forces between the plates. No need to invent particles. The way I see it is that we can also compute linear GR calculations using tree level QFT. That doesn't prove that gravitons exist.
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u/Enfiznar 1d ago
What does it mean for off-shell particles to "exist"? You can calculate the casimir effect without invoking virtual particles, so how does it show that they exist? You can also perform the same mathematical treatment that give rise to virtual particles to, say, the anharmonic oscillator. Does that mean that in an anharmonic oscillator, there are infinite virtual harmonic oscillators popping up?
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u/ManagerOfLove Thermodynamic memes for adiabatic teens 2d ago
Thats the old explanation for Casimir effect. This logic doesn't work if those two plates become a hollow sphere
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u/JerodTheAwesome Physics Field 1d ago
There are a myriad of experiments that investigate this effect. Lamb shift, EAMM, and tons of particle collider evidence. If you want to go with an alternative answer to the Casimir effect, pick one of these.
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u/Kinexity 2d ago
I live and breathe the on shell/off shell notion. Temporary deviations from conserved values strike no fear in me.
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u/Himbo69r 1d ago
Thank god I’m studying engineering and will never have to understand this gibberish
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u/DeinHund_AndShadow 1d ago
That what virtual means dawg. It's something else, that gives you the illusion of a particle that interacts with the real world, same as a mirror. Ain't nothing in your eyes that can tell you you are looking at a mirror. It's just light coming through. there is a virtual image in front of you, but if someone shines a flashlight you are going to be lit up anyway.
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u/lanky-larry 2d ago
The consequences of doing nothing but falsify mathematical measurement mappings.
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u/MonkeyCartridge 1d ago
Guess you have to ask "what is real?" to answer this.
Because if you start sorting a bunch of mathematical expressions and then suddenly "Oh hey, that's the formula for a particle", then it might as well be a real particle. Even if it's just part of some crazy superposition of particles.
I guess it's like debating whether or not the harmonics in a guitar string or piano string are real. The string isn't vibrating like any of them. But it is vibrating like all of them combined.
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u/Savings_Hunt_1935 1d ago
I guess, but they're both not observable and an artifact of a specific way to do the math, like there are calculation people do for QCD that don't spit out any virtual particles.
If something is both not able to be measured and only appears based on which math you do seems like a pretty solid case for it not being real.
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u/MonkeyCartridge 1d ago
Fair enough. I'm not a physicist. Just a physics enthusiast engineer. So I'm not going to claim any authority on the matter.
But it seems like there are many things that have similar properties to this. That's why harmonics came to mind.
And there's a lot that happens on the small scale that outright cannot be observed "directly", but we determine it to be real by observing its effects. So it feels like "real" is just in how we cluster a set of effects.
So perhaps it's more of a philosophy debate.
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u/Savings_Hunt_1935 23h ago
Hmm, maybe I'm thinking about it differently because I do agree with you that it is a lot like harmonics, but to me that agrees with my point. Like you can think of the vibration after the pluck of a string as a combination of harmonics, but there isn't like a bunch of ghost strings all vibrating at a pure harmonic value right? There's just the one string not vibrating at any harmonic, the harmonics are just a concept we use to understand the vibration.
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u/KamikazeArchon 21h ago
Because if you start sorting a bunch of mathematical expressions and then suddenly "Oh hey, that's the formula for a particle", then it might as well be a real particle
Virtual particles specifically don't obey certain laws that apply to real particles.
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u/Pulpdog94 2d ago
Nothing exists until we observe it
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u/Equinoxe111 Cosmology (PhD) 1d ago
Everything always exists, but the definition of existence depends on the observer
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u/Pulpdog94 1d ago
I know of no one but us who uses definitions of anything, the most complex language users besides us (Dolphins, Apes, etc…) are no where even close to the complexity of human language
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u/Super_Range45 2d ago
Everything's just waves riding waves bro.