Are there individual protons and neutrons in a nucleus?(physics.stackexchange.com)
physics.stackexchange.com
Are there individual protons and neutrons in a nucleus?
https://physics.stackexchange.com/questions/828872/are-there-individual-protons-and-neutrons-in-a-nucleus
20 comments
But what new insights does it bring to the table to call different things the same or not?
If you have $10 in a bank account, are those individual dollars or do they all just form an account balance, which is "just" a number.
Electrons in a coherent state are the same. They don't have individual identity. There is just the wave function occupying some area in space.
A similar example is if you hit a key on a piano. This will not only produce the sine wave of the base frequency, but also a number of other frequencies, including overtones and other frequencies that provide timbre.
But these other frequencies are in reality only mathematical artifacts of doing a Fourier transform of the sound pressure from a time domain to a frequency domain.
What is real (if we ignore the molecular level and below) is that a pressure wave is propagated through the air. The individual frequencies of the wave cannot be found anywhere particular in the wave.
Likewise, the exitation of the electron field associated with some atom in a given state will, at every point, represent the combined contribution of ALL electrons.
These electrons are stacked on top of each other the same way the frequencies in a piano tone is or the way the dollars in a bank balance is. They only exist as part of a whole, not individually.
Electrons in a coherent state are the same. They don't have individual identity. There is just the wave function occupying some area in space.
A similar example is if you hit a key on a piano. This will not only produce the sine wave of the base frequency, but also a number of other frequencies, including overtones and other frequencies that provide timbre.
But these other frequencies are in reality only mathematical artifacts of doing a Fourier transform of the sound pressure from a time domain to a frequency domain.
What is real (if we ignore the molecular level and below) is that a pressure wave is propagated through the air. The individual frequencies of the wave cannot be found anywhere particular in the wave.
Likewise, the exitation of the electron field associated with some atom in a given state will, at every point, represent the combined contribution of ALL electrons.
These electrons are stacked on top of each other the same way the frequencies in a piano tone is or the way the dollars in a bank balance is. They only exist as part of a whole, not individually.
But now you introduced an entirely new concept (the electron field), and this is different from saying that all electrons are the same entity.
Electrons (apart potentially from when the wavefunction collapses) do not exist as "particles". They're like a musical "note", simply waves in a field.
And if you do not think the wavefunction collapses (as in the Many World interpretation), "particles" are always just musical notes, just abstractions of the underlying "music"/wave function.
If so, it's fair to say that "all electrons" and "the electron field" is the same thing.
And even if it does collapse, the situation between those collapses is still that we have no indication that electrons exist as "particles" between each collapse.
Edit: Thinking of electrons as "real" between each collapse, is a bit like assuming that a deposit of $10 means the bank actually has 10 $1 bills stored in the vault that are explicitly yours.
The reality is more complicated.
And if you do not think the wavefunction collapses (as in the Many World interpretation), "particles" are always just musical notes, just abstractions of the underlying "music"/wave function.
If so, it's fair to say that "all electrons" and "the electron field" is the same thing.
And even if it does collapse, the situation between those collapses is still that we have no indication that electrons exist as "particles" between each collapse.
Edit: Thinking of electrons as "real" between each collapse, is a bit like assuming that a deposit of $10 means the bank actually has 10 $1 bills stored in the vault that are explicitly yours.
The reality is more complicated.
I respectfully disagree. By saying that all electrons are the same, you are muddying the discussion. It is not helpful to anyone trying to understand what's happening, at both levels of abstraction.
Ok. I'm not sure what angle you come at this from, whether you disagree with my presentation of this (if you know the Quantum Electrodynamics), or some formulation I'm making (if you're not familiar with QED).
If you ARE familiar with QED, I would appreciate it if you point out my error.
If you're not, then I would be interested in knowing what you mean by "both levels of abstraction".
I personally think the Many World Interpretation (MWI) is the most consistent interpretation of Quantum Mechanics (QM). In this interpretation, "electrons" are merely an area of space where the electron field is in an excited state. And in atoms (larger than Hydrogen), it's a bit more excited than where there is just a single electron.
Other QM interpretatons have exactly this math, but hypothesises about wavefunction collapse (which is not needed for the theory to work).
This is the main reason I don't consider individual elementary "particles" to have identity.
There is another, too, that may be more intuitive: In QED, especially in Feynmann diagrams, positrons behave exactly like electrons moving back in time. (This can happen for instance in photon-photon scattering within optical materials).
Now if you simply think such statements don't bring new insights (and you don't know QED), then I suppose this is right, at minimum for you. Which is completely fair. I also find these things really hard to grasp, and that's after spending an fair amount of time wrestling with it in my 20s.
If you ARE familiar with QED, I would appreciate it if you point out my error.
If you're not, then I would be interested in knowing what you mean by "both levels of abstraction".
I personally think the Many World Interpretation (MWI) is the most consistent interpretation of Quantum Mechanics (QM). In this interpretation, "electrons" are merely an area of space where the electron field is in an excited state. And in atoms (larger than Hydrogen), it's a bit more excited than where there is just a single electron.
Other QM interpretatons have exactly this math, but hypothesises about wavefunction collapse (which is not needed for the theory to work).
This is the main reason I don't consider individual elementary "particles" to have identity.
There is another, too, that may be more intuitive: In QED, especially in Feynmann diagrams, positrons behave exactly like electrons moving back in time. (This can happen for instance in photon-photon scattering within optical materials).
Now if you simply think such statements don't bring new insights (and you don't know QED), then I suppose this is right, at minimum for you. Which is completely fair. I also find these things really hard to grasp, and that's after spending an fair amount of time wrestling with it in my 20s.
it brings to the table that electrons in an atom are in fact not different things. The negative part and the positive part of the sine functions are still part of the same function
But saying that X1 and X2 are both part of Y is different from saying that X1 and X2 are the same thing.
> a single particle with mass and charge
FWIW, atomic nuclei have fun substructure. They behave like inhomogeneous sometimes-oblate liquid drops[1] when large, and alpha-particle clusters[2] when small. I wonder if one could craft an introduction to atoms for kids, with rather more "you don't need this for the standardized exams, but here's a bunch of fun stuff you're usually not shown".
[1] a plutonium fission model https://imgur.com/a/nlwzLyy [2] fig.4 on page 4 https://arxiv.org/pdf/1406.2473 Note wacky bowling-pin-shaped Neon.
FWIW, atomic nuclei have fun substructure. They behave like inhomogeneous sometimes-oblate liquid drops[1] when large, and alpha-particle clusters[2] when small. I wonder if one could craft an introduction to atoms for kids, with rather more "you don't need this for the standardized exams, but here's a bunch of fun stuff you're usually not shown".
[1] a plutonium fission model https://imgur.com/a/nlwzLyy [2] fig.4 on page 4 https://arxiv.org/pdf/1406.2473 Note wacky bowling-pin-shaped Neon.
It's useful in the liquid drop model to think of the nucleus as being composed of a multitude of discrete particles. With each particle being an incompressible sphere, the strength of nuclear bonding makes sense as close nucleons interact strongly with eachother while more distant nuclei have weaker interactions, or beyond a certain point no interation, while their electromagnetic charges are not so hindered. It also scales up well for neutron stars, explaining why neutron star density matches nuclear density - in both cases it's just a bunch of piled up nucleons. Isomers make sense as different arrangements of the nucleons, and you can get some isomers with really funky geometries like halo nuclei.
Physicists model heavy-ion collisions at the LHC using fluid dynamic simulations, and to get accurate predictions of final particle correlations, you need to account for the position fluctuations of discrete protons and neutrons within the nucleus.
When you are dealing with anything symbolic it's helpful to understand that all symbols are just concepts and measurements [0], and nothing else. You cannot really reduce the world to 2 dimensions. You need 4 for to describe reality, but then the map becomes the universe.
[0] https://breckyunits.com/scrollsets.html
[0] https://breckyunits.com/scrollsets.html
> You need 4 for to describe reality
+ the dimensions of the quantum fields
+ the dimensions of the quantum fields
to put it another way at the quantum level you are not looking at protons, electrons, neutrons, etc... until you attempt to measure one....
Literally something is solid at our level due to how quantum objects behavior gets up to our macroscopic level.
Or if you want to go further down the rabbit hole....Eastern dualism only is useful at the quantum level....not my words....someone else's.....start with Tao of Physics...yes it is reachable to non math people.
Literally something is solid at our level due to how quantum objects behavior gets up to our macroscopic level.
Or if you want to go further down the rabbit hole....Eastern dualism only is useful at the quantum level....not my words....someone else's.....start with Tao of Physics...yes it is reachable to non math people.
> until you attempt to measure one...
And even then, you are simply getting a measurement of a thing. The true concept you are measuring cannot be reduced to a measurement. Measurements give you a fuzzy picture of concepts, which can be useful, but are always wrong (the real thing is always more complicated and fuzzier)
And even then, you are simply getting a measurement of a thing. The true concept you are measuring cannot be reduced to a measurement. Measurements give you a fuzzy picture of concepts, which can be useful, but are always wrong (the real thing is always more complicated and fuzzier)
> And even then, you are simply getting a measurement of a thing.
This is exactly where the Many World Interpretation and the Copenhagen Interpretation diverges.
If you send a proton with enough violence through the core of a lead atom, for instance, any given observer will see patterns that tend to be interpreted as interactions between nuclei (or quarks, depending on the situation). We can draw Feynmann diagrams for this and even some calculations.
For other particles, such as electron-electron interactions, these can even be quite clean and give the impression that the particle has a certain location at the time of interaction.
While your objection can still be made in this case, it's much weaker. Physicists tend to consider cases like these as an observation of an individual particle. (If they ignore the MWI).
Within the MWI, though, the assumption is that every possible interaction all occur at once. It's just that usually the outcomes are not mutually coherent. And when so, later interactions between the different paths the wavefunction is taking cannot interact with eachother.
In this case, your objection becomes true at a much deeper level.
In any case, we simply do not yet KNOW what exists at the deepest level. All we have is guesses.
This is exactly where the Many World Interpretation and the Copenhagen Interpretation diverges.
If you send a proton with enough violence through the core of a lead atom, for instance, any given observer will see patterns that tend to be interpreted as interactions between nuclei (or quarks, depending on the situation). We can draw Feynmann diagrams for this and even some calculations.
For other particles, such as electron-electron interactions, these can even be quite clean and give the impression that the particle has a certain location at the time of interaction.
While your objection can still be made in this case, it's much weaker. Physicists tend to consider cases like these as an observation of an individual particle. (If they ignore the MWI).
Within the MWI, though, the assumption is that every possible interaction all occur at once. It's just that usually the outcomes are not mutually coherent. And when so, later interactions between the different paths the wavefunction is taking cannot interact with eachother.
In this case, your objection becomes true at a much deeper level.
In any case, we simply do not yet KNOW what exists at the deepest level. All we have is guesses.
You do a great job explaining these concepts, better than most. I have appreciated all of your replies in this post. Do you have a blog or podcast or teach somewhere? I would tune in.
Thx. No podcast though.
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For an even more mind boggling idea, see the one electron universe theory: https://news.ycombinator.com/item?id=40080266