submitted 3 months ago by netvor@lemmy.world to c/science@lemmy.world

Every time I try to understand how forces which hold atoms and molecules together work, I find myself wanting to ask this question: why not the other way around? Could there be an atom which has electrons and neutrons inside, and protons outside?

It feels like a silly question, but is there something we know about the universe we live in that implies that this is not possible?

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[-] liwott@nerdica.net 26 points 3 months ago

Electrons are not subject to the strong nuclear force that glues the protons neutrons together. This means that no attractive force would prevent electric repulsion to scatter a "electron nucleus".

From a field theory perspective, the strong nuclear force is a SU(3) gauge interaction and the electron field transforms as a singlet under that SU(3)

[-] neidu2@feddit.nl 5 points 3 months ago* (last edited 3 months ago)

This was my thoughts to. Electrons don't clump together on their own. Do gluons even affect electrons at all, or is that more of a baryonic thing?

[-] liwott@nerdica.net 12 points 3 months ago

Strong interaction is really designed as a baryonic thing, leptons have no color charge (which is another way to say that they transform as SU(3) singlets). Leptons do not interact with gluons.
Not at tree-level anyway. See for example this list of vertices.

At loop levels, it's possible to imagine an electron decaying into neutrino+W, then W into two quarks who can then interact with gluons, but as it's down a couple of orders in perturbation theory so probably much too weak to hold a nucleus together. Not an expert in particle physics so I do not know with certainty whether a couple-of-loops interaction can have a measurable effect.

[-] billiam0202@lemmy.world 22 points 3 months ago

ELI5 answer: protons and electrons have equal but opposite electromagnetic charges, but they have other qualities that make them dissimilar- for example, protons have a lot more mass than electrons do. It's those other factors that prevent electrons from clumping in the nucleus.

[-] Rhaedas@kbin.social 12 points 3 months ago* (last edited 3 months ago)

From the point of just moving the charge, yes, it's called antimatter. Antielectrons are positive, antiprotons are negative. From the mass point of view though it would be a different kind of physics altogether since electrons have virtually no mass compared to the other two particles, and protons don't exist as a particle-wave duality, so neither protons or electrons would act the same by just switching them out in a Bohr atom model arrangement. Maybe someone with more in depth knowledge can give additional or better reasons.

[-] FlowVoid@lemmy.world 14 points 3 months ago

protons don't exist as a particle-wave

They do, but protons have a much shorter wavelength due to their greater mass.

[-] Fermion@mander.xyz 9 points 3 months ago


Anti hydrogen has been produced and detected in experiments. The energy transition levels are identical to normal hydrogen.

In a newtonian view, two particles orbit the center of mass of the combined system. Since protons are 1836 times as massive as electrons, the "orbit" center would be very close to the proton. So it's a bit like asking what would happen if we swapped the earth and sun. The orbits would change position, but the earth would still orbit the shared center inside the sun at the same orbital radius. So it would look essentially the same as it is currently, just with the center of the system having been shifted by one au.

Clearly I've ignored all of quantum mechanics in this description, but the conclusion is the same. The nucleus and electron both have wavefunctions, but the mass difference makes the spread of the nucleus negligibly small compared to electron orbits. Swapping initial positions and momentum doesn't really change the properties of the system.

[-] HobbitFoot@thelemmy.club 5 points 3 months ago

Because Franklin fucked up the direction.

[-] netvor@lemmy.world 1 points 3 months ago
[-] HobbitFoot@thelemmy.club 1 points 3 months ago

No, I mean Benjamin Franklin.

[-] bjg13@lemmy.world 2 points 3 months ago

If anything, the universe seems to indicate that anything is possible in the multiverse, and that everything that is possible happens somewhere, mayhaps just in a locality we dont have access to. That being said, swapping an elementary particle like the electron for a proton made of quarks would involve corresponding changes to the way the forces worked, which might require a different spacetime geometry, or extra dimensions to make the math of the vibrational modes work. So, that's the most complex way I could think of to say there is no way to prove a negative. And those are all the words I know.

[-] netvor@lemmy.world 5 points 3 months ago

Thing is, trying to do a complete swap, there's a point when the thought experiment kinda eats itself: you end up with a universe which is exactly the same, except the words "proton" and "neutron" are swapped.

The logic of it is fascinating in itself.

this post was submitted on 24 Feb 2024
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