# Can electric charges really be positive and negative?

This question is my extension to this one. Please excuse if it sounds too naive, as I am not a physicist by trade.

From the above linked question and answers to it I understand no physical phenomena or properties in classical mechanics or thermodynamics can be "truly" negative, but only relative to some arbitrary reference point. I'm unsure about electrostatics, though. Electric charge occurs naturally in two elementary forms of a same "size", but opposite "sign". This "sign" is more than just a mathematical fiction; it is physically observable, as attraction resp. repulsion of other charges, depending on their sign. The question for me is whether opposite charges make these entities completely different by nature, or are they simply properties of one and the same entity.

For example, can we say that positron and electron are physically the same object, once carrying a "positive" and once a "negative" charge, or are they different kinds of objects that happen to have a same mass? Something along the lines: "If we flip the spin of an electron, it still remains an electron, but with an opposite spin". Can we make this analogy regarding electron/positron: If we flip the charge of a negatively charged "x-tron" (an electron), it still remains an "x-tron", but with a positive charge?

From my limited knowledge of quantum mechanics, I recon the answer to this last question is "No", implying that even in electrostatics negative numbers are just a mathematical trick we use to simplify descriptions of the nature, but I'd appreciate if someone could confirm that.

I acknowledge that my above reasoning is related to this question, but it is not the same IMO.

• I don't understand how the fact that flipping the charge of an electron turns it into a positron implies that "that even in electrostatics negative numbers are just a mathematical trick we use to simplify descriptions of the nature", and so I don't really get what you want as an answer to this question. Nov 9, 2021 at 11:37
• @ACuriousMind What I meant is that if positron and electron are the same "objects", where the charge is a property, like spin, then talking about "negative charge" makes physically sense. If they are not the same objects, then negative charge means simply an excess of electrons over positrons (or protons, or whatever positively charged particles). Like the "negative pressure" on a membrane simply means that there is an excess pressure on the other side. Can you confirm or deny that electric charge is a property that a particle can acquire and change, like the spin? Nov 9, 2021 at 11:45
• I don't understand what it means for positron and electron to be "the same objects". It is a fact that they only differ in their electric charge. What does it mean for charge to be a "property like spin" as opposed to not being a "property like spin"? Nov 9, 2021 at 11:48
• there is a mathematical phenomena that time reversed matter would have the same effect as being the same with an opposite charge. e.g time reversed electron is mathematically identicle to a positron Nov 9, 2021 at 12:07
• @ACuriousMind My confusion obviously stems from my lack of understanding of particle physics, and, perhaps, from ambiguities of the natural language. I understand that an electron can change its spin. It would still be called "electron". Is there a way to change its charge? For example, can I shoot an electron into a nucleus, turn two of its protons into neutrons and obtain a positron as a result? I've heard of $\beta^+$ and $\beta^-$ decays, but not of the above. Still, would any physical law speak against this possibility? Nov 9, 2021 at 12:39