As I try to understand the elementary particles, I was reading strong interactions and Isospin from a book. Then I came across this:

Thus, the strong interactions do not distinguish between a proton and a neutron. Consequently, if we imagine a world where only the strong force is present, and the weak and electromagnetic forces are turned off, then in such a world a proton would be indistinguishable from a neutron.

Now, I understand this means there is no difference, fundamental in nature between the protons and neutrons. And the charges are not elementary in nature. I'd like someone to explain it to me whether I'm right or not.

  • 2
    $\begingroup$ They are not same. They ACT same way in strong interactions. Example: every 10 kg object falls same way, thus reacting with a gravitational field of earth in the same manner. Which allows us to say that gravitational mass is independent from other properties of objects. Same story with isospin - it is independent from electrical charge of the particle. $\endgroup$
    – Asphir Dom
    Commented Mar 27, 2014 at 4:00
  • $\begingroup$ I don't get the logic in your point....it's not because two persons have the same hair colour that they are identical is it? Same with protons and neutrons, they might have the same interaction under the strong force but other facets of their "personality" such as charge, magnetic spin, mass etc.. tell us they are not the same. $\endgroup$
    – gatsu
    Commented Mar 27, 2014 at 11:28
  • $\begingroup$ Definitely wrong. There are two easily seen fundamental differences: charge and constituent particles (i.e., quarks). Protons have charge; neutrons do not. Protons are made of 2 up quarks and 1 down quark; neutrons are made of 1 up quark and 2 down quarks. $\endgroup$
    – Kyle Kanos
    Commented Mar 27, 2014 at 13:38
  • $\begingroup$ ok.i get it although it is still not clear how can quarks have non integral charge,yet charges are quantized.I think I'll put it up in another question. $\endgroup$
    – vivek
    Commented Mar 27, 2014 at 16:39

2 Answers 2


In the standard model of particle physics, there exist elementary particles out of which all other matter is composed.


elementary particles

The proton and the neutron are composed out of up and down quarks

the proton is (u u d) and the neutron (u d d). If you notice in the table the quarks have different charges. In the hypothetical case of no charges, there will still be the symmetry to which the strong interaction ties the quarks, so a proton and a neutron will still be different, occupying the isotopic spin +1/2 and -1/2 respectively in the representation. They will have the same strong force effects as composites of quarks , following the symmetries.

This is just a statement to demonstrate the isotopic spin symmetry that arises from the strong interactions. Charges are fundamental in nature because we cannot turn them off.


In a non-mainstream theory, the protons are made of electrons and positrons i.e. a nucleus of positrons orbited by electrons with the proton having an excess of one positron and the neutron having equal numbers of electrons and positrons. The theory also claims that the strong and weak interactions are manifestations of the electromagnetic force.

Neutrons and protons would combine to form nuclei with their outer electrons forming nuclear orbitals just like the outer electrons of atoms forming molecular orbitals. The free neutron would be different from the proton and is found to be decay into a proton, an electron and an anti-neutrino. This is understandable because the neutron is like a proton with an extra electron; it just loses that electron to become a proton.

In the combined state, the neutron's extra electron freely rotates within the nuclear orbital leaving the neutron indistinguishable from the proton which is the epitome of stability. This better explains the stability of the neutron in the nucleus.

There's a phenomenon called electron capture where a shell electron is captured by the nucleus. This is easier to understand with the new theory because nuclear orbitals are populated by electrons which means the shell electron would feel at home within the nuclear orbital. But the main reason why a shell electron gets pulled into the nucleus is because there's sufficient positive charge to overcome the repulsive charges between the nuclear electrons and the shell electrons.

Another way of getting rid of the positive charge is to eject one of the positrons in either the neutron or the proton because they look alike anyway.

Check out The One Force of Nature; a free download that explains an alternative theory of science.

  • $\begingroup$ We ask that responses be limited to mainstream physics. There may be value in alternative theories, but this forum is not the place to discuss them. $\endgroup$
    – garyp
    Commented Dec 18, 2016 at 19:08
  • $\begingroup$ OK. I'll find another website. This mutual appreciation website which forces us to accept potentially false theories is best avoided. $\endgroup$ Commented Dec 19, 2016 at 21:40
  • $\begingroup$ This theory isn't even "non-mainstream", it's "not even wrong". To give the simplest example of it's utter failure it can't account for what happens in $\beta^+$ decays—afterall if a neutron contains a proton then a proton can't contain a neutron, but stripped of the observer nuclei that reaction is $p -> n + \beta^+\nu_e$. $\endgroup$ Commented Apr 9, 2017 at 4:10

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