Comment by andy_xor_andrew

No one who has replied to your question has got the right answer. 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.

So, PBS Space Time did a video on this “fine tuned universe” theory and it, like all of their videos, is great. The concept seems to be that in an unbalanced universe, life couldn’t form, and we’d be incapable of having this conversation. So, either there are infinite universes and we exist as a result of being in the right one, or there’s one universe and we exist as a result of the one we’re in being right. Either way, we’re pretty lucky.

https://youtu.be/YmOVoIpaPrc

Imagine you have a bunch of fulcrums in the air and items droping down. If the things that land on the fulcrums don't balance each other out the fulcrum tips and the items keep dropping. Eventually all the fulcrums are balanced.

A lot of these things coalesce until they are stable enough they don't fall apart. If there is a stable form and you have enough of them, eventually you get a lot of stable forms.

It is not some magical thing that makes all this balance, it is more of a settling thing where things eventually drop to a stable state. There is lots of matter that is still unstable.

This is called "charge quantization", and it is not definitively explained by modern theories. There are some very good arguments for it, to be sure, but I don't think they're quite case-closed, of-course-it-must-be-that-way good. It is related to C symmetry, as a discrete symmetry, which ties in to Lorenz invariance and all that, so there's that angle too.

No one knows. That's part of the great mystery.

But also in some sense "it has to be that way," since without charge balance atoms wouldn't exist as we know them, and thus neither would all the chemistry that creates the macroscopic world we inhabit.

Disclaimer: I am not a theoretical physicist (but I am an experimental one...).

If the universe, at the time of the big bang, had no net charge to begin with, and charge is conserved, then it follows that we would have particles whose charge will on net cancel out, and therefore charge would be quantized in some reasonable way. Note that there are doubly charged particles (e.g Delta++) but they're not stable. Some theories do predict fractionally charged particles (millicharged is the term of art) but there is no experimental evidence.

Now, was the universe neutral to begin with? If it wasn't , then that would presumably leave a strong imprint on early universe cosmology. I believe that current measurements of galaxy structure formation, cosmic microwave background and big bang nucleosynthesis probably place extremely strong constraints on early universe neutrality, though there may be caveats I'm not aware of.

There's also a anti-proton which has a negative charge. I think this is probably the smallest charge there is.

A neutron can decay into a proton, electron, and anti-neutrino. So maybe one way to think of it is that a proton is a neutron that is missing an electron, that's why it has the opposite charge of the electron.

Charge is quantized. You cannot have just any amount of electric charge. An electron has three elementary units of negative charge, quarks have -1 and 2. Whether it's a coincidence that proton and electron charge are of the same magnitude (and the neutron is neutral) is another question, but at the elementary level you don't have that much choice for what the charge of a particle is.

It’s even more complicated. The charge on the electron is partially screened by virtual positive charges emerging briefly from the vacuum, so what we measure is less than the actual charge.

I don't know the actual answer, but from my understanding of QFT the answer is going to be roughly this shape:

Charge is not actually a quantity on the real number line; it's more of a "count" of something. Not sure what exactly. The "topological defect" model of charges in 2d is a decent analogy though, in which a charge can be e.g. a count of how many vortices there are in a field which are oriented in a certain direction (picture a bathtub with a bunch of drains, and ask, how many tornado-like vortices, if we count clockwise vortices as +1 and counterclockwise as -1, are there? The number can vary but obviously it has to be an integer because what would half a vortex even mean?)

But that model is too simple for charge, since quarks have +-1/3 or 2/3 but the result always adds up to an integer in a hadron. Maybe it's something like a type of winding number or linking number? I don't know. Whatever it is, when the "correct" explanation is found, it will be obvious why it is always an integer and why its constituents are always 1/3 or 2/3, and it will no longer seem interesting to ask why it can't be any old fraction, because that misunderstands the "type" of object that it is counting.

The fact that the proton has the same charge in absolute value as the electron is just a consequence of the fact that the 8 elementary particles at the lowest energy level, i.e. electron and its neutrino, the 3 up quarks and the 3 down quarks have charges that sum to zero in a 3-dimensional charge space.

These 8 particles and their 8 antiparticles are located in the corners of 2 cubes of unit edge in that 3-dimensional charge space. One cube is in the first octant of the coordinates, with 1 corner in the origin, while the other cube is in the opposite octant, also with 1 corner in the origin.

The neutrino and the antineutrino are in the origin, while the electron and the positron are in the opposite corners of the cubes, in the points (-1,-1,-1) and (1,1,1), and the quarks and the antiquarks are in the 12 off-diagonal corners of the 2 cubes.

As functions of the position vector of a particle in this 3-dimensional charge space, the electric charge is the component of the position vector that is parallel to the cube diagonal that passes through origin and the corners of the electron and positron, while the corresponding component that is orthogonal to the diagonal is the so-called color charge (hence chromodynamics; while the electric forces attempt to make null the 1-dimensional electric charge, the strong forces attempt to make null the 2-dimensional color charge), which is non-null only for the quarks and antiquarks, which are off-diagonal, and it is null for electron, neutrino and their antiparticles.

The projections of the off-diagonal corners of the cubes on the diagonal are at one third and two thirds distances from origin, which is why the electric charges of the quarks are 1/3 and 2/3 in absolute value (where the unit of electric charge is the electron charge, i.e. the diagonal of one unit cube), even if in the charge space all the particles have coordinates that are either 1 or 0 in absolute value.

While this symmetry of the charges is interesting, it is not known why it is so.

In any case, if this symmetry had not existed, the Universe as we know it could not exist, because this symmetry ensures that in the nucleons the total color charge of the quarks is null, so they no longer interact through strong forces (except at very short distances, where the residual forces bind the nucleons into nuclei) and at the next level the total electric charge of the atoms is null, so they no longer interact through electric forces (except at very short distances, where the residual forces bind the atoms into molecules).

The same symmetry exists for the other 2 groups of 8 particles and 2 groups of 8 antiparticles, where the muon and the tauon correspond to the electron, because those particles have greater masses but identical charges with the first groups.

In the initial state of the Big Bang, this symmetry of the charges ensures that even if there were only particles in equal numbers and without any antiparticles, the total electric charge and the total color charge of all matter was null.

While the neutrinos do not contribute to any of the charges, their presence ensures that the total spin, i.e. the total angular momentum, was also null.

> why must protons and electrons be perfectly complementary regarding charge?

According to QED's spin origin of charge, it's because charge comes from spin. What values a particle's spin can take are restricted to certain integer or half-integer values.

Don’t take things described by physical models (proton, electron, the idea of “charge”, etc.) at too much of a face value.

All it is is a web of predictions: we do A then B seems to happen, reliably. We then transform it into a story of sorts, to categorize and classify, find patterns and correlations—that’s just how our minds work—and those models are useful, as they create shortcuts for more useful predictions—but it’s all too easy to start thinking of entities these models describe as if they were real, concrete things (that’s also how our minds work).

I recommend to maintain a sort of Schrödinger’s treatment (they exist if convenient, but otherwise they don’t really) for things described in physical models, because none of the above-mentioned categorization and classification is set in stone. None of it can be proven to be objectively true, unless you have some sort of exclusive access to the fabric of underlying reality that bypasses your consciousness.

With that in mind, you would see that the weird coincidences are not that problematic. It just means there is a better model out there, and that will always be the case.

I don’t think this is a stupid thought at all. It’s a very good question and appreciate all the answers, it’s something I’ve wondered myself

In the same vein, a neutron can decay into a proton, an electron and a neutrino (Beta decay), so in some sense the neutral neutron is the combination of an electron and proton. (A connection is there?)

In a simplistic way, I see a neutron star as just being a lump of regular (atomic) matter where the high pressure has forced all the electrons into the protons.

Question for someone who might know: Was pressure so high in the early universe that matter originally formed as neutrons, then as pressure reduced electrons and protons were able to separate? Sort of like the formation of a neutron star in reverse?

First, I am not a physicist. That said, he's my attempt at an answer that satisfies me: Part of the reason is charge quantization. Neither could be some fractional charge. We also observe charge conservation and electromagnetic force laws as described by quantum electrodynamics (QED). These necessitate that the electron and proton charges be precisely balanced for the universe to function as it does.

Not a physicist at all but I'd offer the following thoughts on the question of "why":

- Take a neutron, pull out an electron (and an antineutrino), and you're left with a proton.

- Asking why protons and electrons are so different is a little bit like asking why hydrogen and iodine have exactly opposite charges even though iodine is so much more complex: they're made of different things

https://youtu.be/36GT2zI8lVA

Richard Feynman on why questions

At the end of the day loads of these types of questions boil down to the anthropic principle. If it didn’t work out so that things could be stable, nothing would be asking the question.

That’s not a satisfying answer but we don’t have a better one in the realm of science. All we have left is either randomness/serendipity or spirituality/religion.

First-principles question from an ignorant thinker: why couldn't it be that the presence of +/-e in one of them is due to the subtraction of +/-e in the other? Do we know anything about the finer details of quarks and electrons beyond what we currently can resolve?

Maybe think of it more simply, one precedes the other, this much positive charge in one place attracts negative charge of equal magnitude around it: if you send more electrons (and to be honest, talking of positive charge for a proton is a bit wrong: a positive charge being the absence of electrons... and electrons giving the "negative" charge as they add up), they'll detach and push away those that were already there.

There is nothing convenient, it's as logical as saying that you were tshirts when you go out: there is nothing extraordinary that one torso = one tshirt, as having two or zero tshirts wouldn't help: 0 would make you want one more tshirt, 2 would make you want to remove one.

In a "grand unified theory" (which does not include gravity) the strong, electromagnetic and weak forces are unified into one gague theory. SU(5) is one choice. In these theories, the electron, quark and neurtinos fit together as if they were different versions of the same particle, just as in the standard model the up quark has three "colors". In these theories there is a well defined relation between the charges. You can lookup the SU(5) unified theory to see more. I would say these theories are widely believed, but we have not managed to put them all together yet.

There’s a few good “particle zoo” videos out there for the building blocks.

I took some advanced courses and from my understanding it comes down to the pieces that make up protons and electrons. In the quantum realm it adds some fuzziness to the answer by introducing quarks. The net charge may be one thing but I would defer to a physics paper for a deeper understanding.

https://physics.stackexchange.com/questions/21753/why-do-ele...

Something...something...gauge theory.

Or perhaps -- it's a constant in the simulator source code.

So first off: charge is quantized. Glossing over some weird particles (like quarks) which can't exist by themselves an integer multiple of e as their charge.

It's been a while since I finished undergrad so my knowledge is rusty, but I don't recall any isolatable particles whose charge wasn't -1e, 0, or 1e. If that's the case, the easiest explanation for why they have the same charge is that if they didn't have opposite charges there wouldn't be anything holding them together in an atom.

I believe the end of my physics textbook in college just said “be grateful that the charge on the electron is what it is because without it our universe wouldn’t exist if it was even slightly different” or something to that effect.

Our universe may be the trillionth trillionth one created and we are in an anthropomorphic universe just like we are on an anthropomorphic planet. It always makes me grateful.

>The charge on a proton is +1.602 x 10-19 C, and the charge on an electron is -1.602 x 10-19 C.

>why must protons and electrons be perfectly complementary regarding charge? if the proton is this insanely complex thing, by what rule does it end up equaling exactly the opposite charge of an electron?

Perhaps "complexity" and "anti-complexity" are the forces that attract. Order and chaos. To have one you must have the other. Without both nothing about this universe would work.

Sorry, I'm high.

One thing to note is that up and down quarks are separated by exactly one unit of charge (2/3 is 1 more than -1/3).

The charge coincidence is one of the reasons that scientists are looking for a grand unified theory -- part of which would ultimately mean that in some sense quarks and electrons are _the same thing_, and the electroweak and strong forces would be unified.

I'll take a shot at this. The "answer," such as it is, is symmetry. The electron belongs to a group called the leptons, which is to say they are lightweight. Leptons obey certain sorts of statistics and consist of the electron, the muon, the tau lepton, the electron neutrino, the muon neutrino, the tau neutrino, and their antiparticles. That's twelve in total.

The mirror of the leptons would be quarks. Up, down, charm, beauty, top, and bottom ... and their antiparticles. Twelve again! Their charges are 2/3e, -1/3e, 2/3e, -1/3e, 2/3e, -1/3e, and the reverse for the antiquarks. One bundle of three quarks is the proton, and it happens to be 2/3e + 2/3e + -1/3e. But so what? There's all kinds of other bundles. Three-quark bundles are typically hadrons (heavyweight) and two-quark bundles are mesons (medium weight). So you have a lot of choices on the other side!

The choices are caused by something called color confinement, which states that you will not get quarks alone. Indeed, you can take a pair of quarks in the aforementioned meson, and if you stretched them further and further apart, when the bond between them (mediated by gluons) snapped, you would have put so much energy into the stretching and snapping to create two new quarks, one at each end of your broken rubber band. Just as you cannot cut a piece of string such that it only has one end, so you have it with color confinement. I don't want to get too far away from the main point but because of this, quarks are found (normally, outside of Big-Bang quark-gluon plasmas) in combination ... and so eventually one of the combinations has a charge number resembling that of the electron.

Also, positrons aren't really the opposite of electrons. They're opposite on the matter/antimatter axis, which automatically flips the charge, q. They are not opposite along the lepton-quark axis, nor are they opposite along the electron-neutrino axis. Instead of one mirror, imagine many mirrors at angles to one another, and "opposite" becomes a less useful term.

I think we simply observe the most stable states of existence which preclude asymmetry and all other states of matter have either gone extinct, or are so fickle that we can only observe them momentarily. So the deep truth behind why and what exists and what cannot is pretty straightforward.

A simple answer could be that there is an elementary charge. No free particle can have less than this charge and charges are quantized in terms of this elementary charge.

This is in opposition to e.g. mass. There is no elementary mass, and so no particles need to have the same mass.

Huh. It would make a lot more sense if the "complicated" proton was +3 and always paired with three "simple" -1 electrons. Maybe someday we'll find the electron is really three of some even more fundamental particle.

Electrons balance the nuclear charge by their distance from the nucleus. They’re not perfectly equal; the electrons move closer or farther to maintain balance with the nucleus. I think it’s called effective nuclear charge.

Why does light decay quadratically and not linearly? Why are the laws of physics algebraic at all? Why did the Big Bang happen? Ask enough why's and get to: we just don't know. Turtles all the way down.

Maybe the proton is not complex but the process to probe it is. Proton is an aggregate of emergent phenomena like mass and its resultant properties. For a simplistic model assume that proton is a tetrahedron with energy wave generators at the vertices and how those waves interact with each other creates the emergent phenomena like mass, charge etc. It will be difficult to probe such a tetrahedron by just studying the properties of the waves and the peaks in those waves/interference which are perceived as particles by the probes.

Are there intermediate [electron,] charge states between + and - in superfluids and/or superconductors?

Is there superposition with electron charge states?

Maybe that was a form of matter that was stable early in the history of time and matter, and so it survived, but others didn't?

Because if it were any other way then you wouldn’t exist to sit there and ponder the question. That’s the unsatisfying answer.

I think it makes sense to draw an analogy to evolution—stable arrangements of elementary particles that (somehow) reinforce similar arrangements around them will come to dominate the observable universe.

> give me a religious explanation that isn't a religious explanation

Then I’ll ask why can’t you use protons as electricity?

Checkmate, atheists

You would think that with my username, I should know the answer. But I have no clue

I mean it's not that complicated to understand. e is just a physical constant. It's been measured as such, with varying degrees of precision. The creator is as lazy a programmer as we are. To make the math work, + and - are used.

friendly suggestion, avoid describing yourself as "not a smart person". Research definitely shows that self-talk can have significant effects. I know this from my own life and experiences, but for the sake of writing this response I asked ChatGPT to look up some research to back me up:

"Sure, positive and negative self-talk can have significant effects on various aspects of mental health, performance, and well-being. Here are some scientific research findings on this topic:

Impact on Stress and Coping Mechanisms:

Research suggests that positive self-talk can help individuals cope with stress more effectively by promoting adaptive coping strategies and reducing negative emotional responses. Conversely, negative self-talk is associated with increased levels of stress and maladaptive coping behaviors such as avoidance (Hanssen, M., Vancleef, L., Vlaeyen, J., & Peters, M., 2013).

Influence on Performance:

Studies have shown that positive self-talk can enhance performance in various domains such as sports, academics, and professional settings. Positive self-talk is associated with increased confidence, motivation, and persistence, leading to improved performance outcomes. Conversely, negative self-talk can undermine performance by inducing self-doubt, anxiety, and distraction (Hardy, J., Hall, C., & Hardy, L., 2004).

Effects on Mental Health:

Positive self-talk is linked to better mental health outcomes, including higher levels of self-esteem, resilience, and subjective well-being. On the other hand, negative self-talk is associated with symptoms of depression, anxiety, and lower overall psychological functioning (Marshall, S., Parker, P., Ciarrochi, J., Sahdra, B., Jackson, C., & Heaven, P., 2015).

Physiological Responses:

Research suggests that self-talk can influence physiological responses such as heart rate, cortisol levels, and immune function. Positive self-talk is associated with reduced physiological arousal and stress reactivity, whereas negative self-talk can trigger a stress response and impair immune function (Penley, J., Tomaka, J., & Wiebe, J., 2002).

Neurological Correlates:

Neuroimaging studies have identified neural correlates of self-talk, showing that positive self-talk activates regions of the brain associated with reward processing, cognitive control, and emotional regulation. In contrast, negative self-talk is linked to increased activity in brain regions involved in threat perception and emotional reactivity (Morin, A., & Uttl, B., 2013)."

Anyway, I'm sure you're not beating yourself up all the time about being a dummy, but like I said in the beginning of this response, just a friendly suggestion about mindset and word-choice :)

How can you ask that and also claim to not be a smart person lmao

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I'm not an expert, but e is the smallest possible charge, so you can't have a fraction of it, probably related to to Plank constant.

Edit: after verification, the smallest possible charge is e/3 (the quantum charge), e is the elementary charge.

A relevant link to for the question:

https://en.wikipedia.org/wiki/Elementary_charge?useskin=vect...