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Two up quarks in a proton lead to an imbalance, which results in the proton having the ability to attract electrons. Two down quarks in a neutron lead to balance in the electromagnetic force, leading to no interactions happening with electrons. The strong force and electromagnetic force appear to be directly related. Unless I am misunderstanding something, it appears that a particular arrangement of quarks leads to a specific kind of baryon that has a specific kind of electromagnetic behavior - meaning the strong force is indirectly leading to the behavior of the electromagnetic force.

I don't understand why the electromagnetic force is considered to be a separate force than the strong force for the following reasons:

  1. Quarks clump together to form baryons due to the strong force, not the electromagnetic force.
  2. I understand that quarks have electromagnetic charges, but I don't understand whether the cause for this is due to it "fitting into the math" or it actually being a fundamental property of the quarks.
  3. I understand that the strong force overpowers the electromagnetic force, but how do we know for certain that quarks even have charges?

Any insights or references would be greatly appreciated! Thanks for reading.

So, my question is: why is the electromagnetic force considered separate than the strong force?

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  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Commented Aug 18, 2023 at 22:42
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    $\begingroup$ Along with the below answer, you'd have to explain the fact that the charged leptons are colorless and yet have a nonzero electric charge. $\endgroup$
    – Triatticus
    Commented Aug 18, 2023 at 23:07
  • $\begingroup$ related: physics.stackexchange.com/questions/60356/… $\endgroup$
    – g s
    Commented Aug 18, 2023 at 23:28
  • $\begingroup$ @Community I clarified my question at the end. Apologies. $\endgroup$
    – xxl
    Commented Aug 19, 2023 at 2:09
  • $\begingroup$ @Triatticus That helped me understand the separation further. I suppose where an area of my confusion lies is if the strong force creates the conditions which later attract electrons, couldn't there be some fundamental effect of the strong force that creates the foundation of the electromagnetic force? $\endgroup$
    – xxl
    Commented Aug 19, 2023 at 2:40

1 Answer 1

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Looks like you threw all the pieces on the table, expecting them to magically cohere, without the method in their madness that makes the standard model so special...

  1. I understand that the strong force overpowers the electromagnetic force, but how do we know for certain that quarks even have charges?

The 1990 Nobel prizes celebrate the deep inelastic scattering experiments of electrons on nucleons which proved that, in the late 60s and early 70s of the previous century. Analyzing the scattering profiles, it is possible to firmly deduce, "for certain", there are three charged quarks in the proton and neutron, exchanging virtual photons with the bombarding electrons thrown at them.

  1. Quarks clump together to form baryons due to the strong force, not the electromagnetic force.

Indeed, even though EM is weaker than the strong force binding such quarks, electrons, rarely, knock such off the nucleons and produce more hadrons, flying off in angles systematically dispositive of the established picture. A kinematic microscope of sorts.

The strong force and electromagnetic force appear to be directly related. Unless I am misunderstanding something, it appears that a particular arrangement of quarks leads to a specific kind of baryon that has a specific kind of electromagnetic behavior - meaning the strong force is indirectly leading to the behavior of the electromagnetic force.

You start the paragraph by asserting a direct relation, and finish it appreciating the relation is indirect: which is the proper perspective. The strong force binds charged quarks, and when, coincidentally, the net nucleon charge vanishes, the net electric force is zero. The net magnetic interaction is not, as the neutron has a huge, fat, magnetic moment. The charge of quarks is sort of like the hair color in dogs; not particularly "emergent" or otherwise deeply significant. Many particles have a charge or not, even leptons or gauge bosons which do not interact strongly.

The electromagnetic force is considered to be a separate force from the strong force--even though some speculative theories, GUTS, imagine them to be connected at fantastically high energies (the kinetic energy of a bus, all concentrated in a particle region) beyond our everyday experience or labs.

  1. I understand that quarks have electromagnetic charges, but I don't understand whether the cause for this is due to it "fitting into the math" or it actually being a fundamental property of the quarks.

I can't tell the difference between the two non-exclusive alternatives. The quarks are what they are, and they fit into the sudoku math Gell-Mann and Zweig (and others) discovered in the mid 60s. They are part of the astounding math (including anomaly cancellation) that was eventually appreciated about the standard model. Galileo said that "the book of nature is written in math". Once you study it, it should blow your mind...

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  • $\begingroup$ Thanks for the answer, @cosmas-zachos. A few questions: 1. How does an electron knocking a quark out of place produce a hadron? 2. I don't understand why an electron knocking a quark off the nucleons means the forces are separate. Is the electron interacting with the quark via the electromagnetic force? 3. The reason leptons and gauge bosons do not interact strongly is due to them lacking color charges, correct? 4. Couldn't the connection between the forces be weaker at lower energies, and less obvious? Your answer helped me understand parts that I am missing. Thanks again :) $\endgroup$
    – xxl
    Commented Aug 19, 2023 at 2:31
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    $\begingroup$ @Uni physical observations can only be modeled with mathematics, not with words. Mathematics is the language of physics. It is not enough to be curious in words, in order to address all your new questions questions one needs the theoretical mathematical model.. $\endgroup$
    – anna v
    Commented Aug 19, 2023 at 4:11
  • $\begingroup$ 1. the struck quark flies off at a telltale angle and then "dresses" itself with other created quarks and antiquarks into a hadron, through the strong interaction. 2. Yes. It gets knocked off electromagnetically, and then hadronizes strongly. 3. Correct. 4. At lower energies the connection between EM and strong, if it existed would be quite non-obvious. $\endgroup$
    – Cosmas Zachos
    Commented Aug 19, 2023 at 11:22

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