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No one who has replied to your question has got the right answer. https://physics.stackexchange.com/questions/21753/why-do-electron-and-proton-have-the-same-but

No one who has replied to your question has got the right answer. https://physics.stackexchange.com/questions/21753/why-do-electron-and-proton-have-the-same-but-opposite-electric-charge https://physics.stackexchange.com/questions/21753/why-do-ele... has the right answer. There are multiple aspects to this argument, but essentially, the symmetries of your system force the charges in the Standard Model (quarks and leptons) to be the way they are due to gauge anomaly cancellation. If you believe in quark confinement, which is extremely well motivated, computationally, theoretically and experimentally, then the fact that the proton has exactly charge +1 follows naturally.

polskibus 3y ago
Which answer on physicsexchange is the right one? The top scored ?
- guenthert 3y ago
  The top scored is just the answer liked best. The fact that it refers to proton decay and quantum gravity, both hypotheses which, as plausible as they might be, are not experimentally testable at this time, renders in my mind the confidence of the answer questionable.
  - importantstuff 3y ago
    The top answer has multiple reasons. The one I am referring to in particular is this section: "I should point out that if you believe that the standard model matter is complete, then anomaly cancellation requires that the charge of the proton is equal to the charge of the positron, because there is instanton mediated proton decay as discovered by t'Hooft, and this is something we might concievable soon observe in accelerators. So in order to make the charge of the proton slightly different from the electron, you can't modify parameters in the standard model, you need to add a heck of a lot of unobserved nearly massless fermions with tiny U(1) charge." It makes no reference to quantum gravity.
  - feoren 3y ago
    > The fact that it refers to proton decay ... You don't need spontaneous proton decay for the answer to work, just positron emission: https://en.wikipedia.org/wiki/Positron_emission https://en.wikipedia.org/wiki/Positron_emission
hansbo 3y ago
I am reading this as "it has to be this way, or the model does not hold", but it does not explain why. What causes it? Consistency of a model cannot be the ultimate reason, right?
- coldtea 3y ago
  Not a physisist, but "consistency with the model" doesn't mean "because that's how some arbitrary model says it should be". It's more like: "Because we have arrived at a model that describes well most other aspect of those particles and their behavior, and has verified predictive power, and given the constrains and calculations based on that model, that's what its charge would be".
  - awestroke 3y ago
    Still does not explain "why"
    - ruszki 3y ago
      There are causal links, but we always have axioms for which either there is no reasons, they are just how they are, or we don't know the reasons, we have just experimental evidence for them. At the end, the answer to "why" is always, because they are just how they are.
    - chaxor 3y ago
      I just would like to point out that "why" is not a scientific question. Feynman mentions this quite a lot. The question "why" doesn't have answers in science. A question of "How" has a better chance of being answered in science.
      - foldr 3y ago
        I think that was a fairly idiosyncratic point of view of Feynman's. In actual scientific practice you can find hundreds of examples of published scientific papers that address 'why' questions. Here are a couple of completely random examples: https://link.springer.com/article/10.1007/s11207-009-9338-5 https://link.springer.com/article/10.1007/s11207-009-9338-5 https://www.mdpi.com/2624-8174/4/3/63 https://www.mdpi.com/2624-8174/4/3/63
dontupvoteme 3y ago
Wait, proton decay was proven?
- feoren 3y ago
  "Decay" is an unfortunate historical word for what are essentially bidirectional pathways between groups of particles. It usually just means "transform". We know a proton can transform into a neutron, positron, and (electron) neutrino in "beta plus decay" (and the reverse can also happen, and all sorts of other things). This is all the answerer means when they say "decay". When this transformation occurs, all conservation laws must hold; in particular, charge conservation. Therefore charge(neutron) + charge(positron) + charge(neutrino) == charge(proton), and we know charge(neutron) and charge(neutrino) are zero, so charge(positron) == charge(proton). I suppose it's possible we don't have a full picture of beta-plus decay, and there's some nearly undetectable fourth particle carrying off a tiny bit of charge, but my understanding is that a lot of the rest of our understanding of particle physics would have to be wrong for this to be the case. This is not the same as "spontaneous proton decay", which has not been observed.

polskibus 3y ago

Which answer on physicsexchange is the right one? The top scored ?

guenthert 3y ago
The top scored is just the answer liked best. The fact that it refers to proton decay and quantum gravity, both hypotheses which, as plausible as they might be, are not experimentally testable at this time, renders in my mind the confidence of the answer questionable.
- importantstuff 3y ago
  The top answer has multiple reasons. The one I am referring to in particular is this section: "I should point out that if you believe that the standard model matter is complete, then anomaly cancellation requires that the charge of the proton is equal to the charge of the positron, because there is instanton mediated proton decay as discovered by t'Hooft, and this is something we might concievable soon observe in accelerators. So in order to make the charge of the proton slightly different from the electron, you can't modify parameters in the standard model, you need to add a heck of a lot of unobserved nearly massless fermions with tiny U(1) charge." It makes no reference to quantum gravity.
- feoren 3y ago
  > The fact that it refers to proton decay ... You don't need spontaneous proton decay for the answer to work, just positron emission: https://en.wikipedia.org/wiki/Positron_emission https://en.wikipedia.org/wiki/Positron_emission

hansbo 3y ago

I am reading this as "it has to be this way, or the model does not hold", but it does not explain why. What causes it? Consistency of a model cannot be the ultimate reason, right?

coldtea 3y ago
Not a physisist, but "consistency with the model" doesn't mean "because that's how some arbitrary model says it should be". It's more like: "Because we have arrived at a model that describes well most other aspect of those particles and their behavior, and has verified predictive power, and given the constrains and calculations based on that model, that's what its charge would be".
- awestroke 3y ago
  Still does not explain "why"
  - ruszki 3y ago
    There are causal links, but we always have axioms for which either there is no reasons, they are just how they are, or we don't know the reasons, we have just experimental evidence for them. At the end, the answer to "why" is always, because they are just how they are.
  - chaxor 3y ago
    I just would like to point out that "why" is not a scientific question. Feynman mentions this quite a lot. The question "why" doesn't have answers in science. A question of "How" has a better chance of being answered in science.
    - foldr 3y ago
      I think that was a fairly idiosyncratic point of view of Feynman's. In actual scientific practice you can find hundreds of examples of published scientific papers that address 'why' questions. Here are a couple of completely random examples: https://link.springer.com/article/10.1007/s11207-009-9338-5 https://link.springer.com/article/10.1007/s11207-009-9338-5 https://www.mdpi.com/2624-8174/4/3/63 https://www.mdpi.com/2624-8174/4/3/63

dontupvoteme 3y ago

Wait, proton decay was proven?

feoren 3y ago
"Decay" is an unfortunate historical word for what are essentially bidirectional pathways between groups of particles. It usually just means "transform". We know a proton can transform into a neutron, positron, and (electron) neutrino in "beta plus decay" (and the reverse can also happen, and all sorts of other things). This is all the answerer means when they say "decay". When this transformation occurs, all conservation laws must hold; in particular, charge conservation. Therefore charge(neutron) + charge(positron) + charge(neutrino) == charge(proton), and we know charge(neutron) and charge(neutrino) are zero, so charge(positron) == charge(proton). I suppose it's possible we don't have a full picture of beta-plus decay, and there's some nearly undetectable fourth particle carrying off a tiny bit of charge, but my understanding is that a lot of the rest of our understanding of particle physics would have to be wrong for this to be the case. This is not the same as "spontaneous proton decay", which has not been observed.