How many different charges are there in nature and why?

[mark!]

Protons are +1 charged, electrons -1, so that's makes two charges, but how does antimatter charge relate to normal matter charge?

 

[jedishrfu]

From this article, the charges are considered equivalent between matter and anti-matter:

https://en.wikipedia.org/wiki/Antiparticle

Quarks have fractional charge but since they are never seen outside of a group that doesn't count:

https://en.wikipedia.org/wiki/Quark

Properties
Electric charge
See also: Electric charge
Quarks have fractional electric charge values – either  1⁄3 or  2⁄3 times the elementary charge (e), depending on flavor. Up, charm, and top quarks (collectively referred to as up-type quarks) have a charge of + 2⁄3 e, while down, strange, and bottom quarks (down-type quarks) have − 1⁄3 e. Antiquarks have the opposite charge to their corresponding quarks; up-type antiquarks have charges of − 2⁄3 e and down-type antiquarks have charges of + 1⁄3 e. Since the electric charge of a hadron is the sum of the charges of the constituent quarks, all hadrons have integer charges: the combination of three quarks (baryons), three antiquarks (antibaryons), or a quark and an antiquark (mesons) always results in integer charges.[57] For example, the hadron constituents of atomic nuclei, neutrons and protons, have charges of 0 e and +1 e respectively; the neutron is composed of two down quarks and one up quark, and the proton of two up quarks and one down quark.[12]

 

[Nugatory]

Protons are +1 charged, electrons -1, so that's makes two charges, but how does antimatter charge relate to normal matter charge?

Antiprotons have the same charge as electrons and antielectrons (positrons) have the same charge as protons, so still just two kinds of charge: positive and negative.

 

[mark!]

Alright, so the answer is two. Nature consists of two charges. Thanks! But why? Why is this logical and understandable? What’s the fundamental difference between the two, spin?

 

[Nugatory]

Alright, so the answer is two. Nature consists of two charges. Thanks! But why?

There's no better answer to that question that "Because that's how the universe we live in works". The goal of science is to discover the laws that govern the behavior of our universe, but discovering them doesn't tell us much about why the universe is governed by one set of laws instead of another.

It's tempting to think that there is some deeper law that explains why the number of charges must be two instead of something else, but even if we discover that hypothetical law we've just pushed the problem down one level: Why that law, and not some other that allows the number of charges to be three, or seven, or twenty-nine, or ...? And even if we could answer that question, we'd just be down yet another level with another "why?" question - eventually we always run into "because that's the universe we live in".

 

[mark!]

@Nugatory Agree, but if nature produces only two charges, called matter and antimatter, then why are there (in the 1st generation) up and down quarks, as well as anti quarks? To me, that implies a third charge.

 

[Drakkith]

@Nugatory Agree, but if nature produces only two charges, called matter and antimatter, then why are there (in the 1st generation) up and down quarks, as well as anti quarks? To me, that implies a third charge.

Take care with your terminology. The are only two electric charges, positive and negative, and these have no known relationship with the number of different particles which exist except that some of the particles have non-zero electric charge and some do not.

In addition to electric charge, there are numerous other properties of particles, such as spin, mass, color charge, and more. Trying to determine how these different properties are related is a very complex task and the fact that there exists similar particles differing only slightly in their mass and makeup does not necessarily imply that there is another undiscovered property lurking out there waiting to be found.

 

[mark!]

Take care with your terminology. The are only two electric charges.

What charge in nature is not electric?

 

[Drakkith]

What charge in nature is not electric?

Again, we must be careful with terminology. We have assigned to particles various properties that we use to describe how they interact with each other. One of these is called electric charge. Particles with non-zero electric charge will feel a force from other particles with non-zero electric charge and will interact with the electromagnetic field (we can call these interactions "electromagnetic interactions"). Moreover, these interactions are governed by specific rules. Particles without electric charge do not follow these rules. For example, a neutrino, with an electric charge of zero, does not feel a force from an electron via electromagnetic interactions.

However, there are other properties and rules by which particles can interact. Neutrinos, while not interacting electromagnetically, can interact with electrons through the "weak interaction" or "weak force". There are certain rules governing interactions via the weak force and these rules are different from those governing electromagnetic interactions. One difference is that we do not have a "weak charge".

However, we do have another force which does have charges. The "strong force" is the force by which quarks and nucleons interact. It has multiple charges divided into two sets of three "color charges" (which have no relation to actual colors you perceive in vision). The first set of three are labeled red, green, blue and the second set is labeled anti-red, anti-green, and anti-blue. Given that there are six different charges instead of two, the rules governing the strong force are much more complicated than the rules governing electromagnetism.

 

[mark!]

@Drakkith The charge distribution inside an atom is complex, of course, but why shouldn't it therefore be electric, even though sometimes the over all net charge can be 0? I don't understand why this shouldn't be the case. What about the chargeless neutrino, or the Z boson, they have mass but no charge, so they might kind of behave like a neutron does, which is: combining opposite charges together (up and down quarks) to make a net charge of 0. If a particle has a 0 net charge, it doesn't automatically mean that it can't consist of any charged components (just like is the case with the neutron, because all its quarks are charged). So when you say "The are only two electric charges" (implying that charges might exist in nature that are not electric), I don't know how to interpret such a statement. Could you give an example of a non electric charge in nature?
And what is your perspective on the down antiquark in a (pi) meson? Why do we call this quark "antiquark", when quarks could only be + or - charged?

@harrylentil I think it's deeply mysterious that two fusing protons can release/create antimatter (positrons), so there's some kind of antimatterness 'locked up' inside or something, but I don't really understand how.

 

[Drakkith]

@Drakkith The charge distribution inside an atom is complex, of course, but why shouldn't it therefore be electric, even though sometimes the over all net charge can be 0? I don't understand why this shouldn't be the case. What about the chargeless neutrino, or the Z boson, they have mass but no charge, so they might kind of behave like a neutron does, which is: combining opposite charges together (up and down quarks) to make a net charge of 0. If a particle has a 0 net charge, it doesn't automatically mean that it can't consist of any charged components (just like is the case with the neutron, because all its quarks are charged).

The neutron is indeed electrically neutral (zero net electric charge), but it is a composite particle, composed of fundamental particles with non-zero electric charge. Since, by definition, fundamental particles are not composed of other particles, an electrically neutral fundamental particle like a neutrino is not composed of electrically charged particles which happen to cancel out each other's charges. So yes, fundamental particles like the Z boson and the neutrino are neutral because they are truly neutral, not because they have canceling electric charges within themselves.

Note that although we've defined what a fundamental particle is, we are required to experimentally verify that a particle is not composed of other particles in order to classify it as a fundamental particle. All particles currently classified as fundamental have been checked by experimentation and have been verified to the best of our current ability. In the future, we may find that some or all of these particles are not fundamental, but as of right now they are classified as such.

So when you say "The are only two electric charges" (implying that charges might exist in nature that are not electric), I don't know how to interpret such a statement. Could you give an example of a non electric charge in nature?

I already gave one in my previous post. The color charge of particles which interact via the Strong Force.
For a broader explanation of charge, see this article: https://en.wikipedia.org/wiki/Charge_(physics)

And what is your perspective on the down antiquark in a (pi) meson? Why do we call this quark "antiquark", when quarks could only be + or - charged?

Because it is the antiparticle of the down quark? I don't really understand your question. A quark is a type of fundamental particle which interacts via the strong force, the electromagnetic force, the weak force, and gravitation. All four of the fundamental force of nature. There are three "generations" of quarks consisting of two different quarks per generation. The 1st generation consists of the up quark and the down quark. Each quark also has a corresponding antiparticle which has the same mass but opposite electric charge, baryon number, isospin, and hypercharge. The last three are additional properties we've assigned to quarks to distinguish them from one another. A down antiquark has an electric charge + 1/3 instead of -1/3, a baryon number of -1/3 instead of + 1/3, an isospin of +1/2 instead of -1/2, and a hypercharge of -1/3 instead of + 1/3.

@harrylentil I think it's deeply mysterious that two fusing protons can release/create antimatter (positrons), so there's some kind of antimatterness 'locked up' inside or something, but I don't really understand how.

Particle creation and annihilation take place all the time and can generate both matter and antimatter, even at the same time. For example, beta decay creates both an electron and an electron anti-neutrino. In addition, particle creation does not require that the created particle exist somehow inside a parent particle. Pair production creates an electron and a positron from a single photon, yet electrons and positrons do not somehow exist inside photons. We don't find extra electrons and positrons in our antennas and receivers when we listen to the radio.

I don't find any of this any more mysterious than the rest of the laws of physics are.

 

[mark!]

Since, by definition, fundamental particles are not composed of other particles

This is where you lost me, how can undividable particles, like quarks, be fractionally charged? It's the smallest of the smallest, point particles, fundamental particles, just like bits in a byte (a bit means ON or OFF, 1 of 0, + or -), so how can you argue that a 2/3 charged particle can be a fundamental (undividable) particle?

All particles currently classified as fundamental have been checked by experimentation and have been verified to the best of our current ability

I think that this doesn't prove that they are to be considered fundamental until proven differently, but rather the other way around. On the other hand, you said:

Pair production creates an electron and a positron from a single photon, yet electrons and positrons do not somehow exist inside photons

So that means that a photon must have some kind of dualistic characteristic, because it's able to divide. And this dualistic characteristic might be matter/antimatter (because the anti particle of a photon is a photon, not an anti photon).

That's why I think that the fundamental particles can't all be fundamental, in contrast with what you're saying. Maybe Planck length/charge/volume particles exist, 1 dimensional "strings", just like string theory predicts, because there's no shorter length than Planck length. Maybe the current ability of human kind is not able to detect, measure and prove it, but we might however logically deduct it with 100% certainty, the same way we logically concluded that dark matter exists.

 

[jbriggs444]

This is where you lost me, how can undividable particles, like quarks, be fractionally charged? It's the smallest of the smallest, point particles, fundamental particles, just like bits in a byte (a bit means ON or OFF, 1 of 0, + or -), so how can you argue that a 2/3 charged particle can be a fundamental (undividable) particle?

For the same reason that the charge on an electron is -1 and not +1. Historical consistency.

 

[Mister T]

Alright, so the answer is two. Nature consists of two charges. Thanks! But why? Why is this logical and understandable? What’s the fundamental difference between the two, spin?

Electric charge is something that people invent to describe the way particles interact. The interaction can be either attractive or repulsive, so a scheme where two kinds of electrical charge is used to describe that. We say "opposite charges attract" and "like charges repel". Note that you need two kinds of charge in such a scheme. So the fundamental difference is that they're labels.

There are other kinds of interactions besides electrical, for example, gravitational. The gravitational interaction is always attractive so you need only one kind of "gravitational charge". We call it mass.

For the strong interaction the notion of "color charge" is used. There are three kinds of color and three kinds of anti-color.

It's all a scheme invented by humans to describe what we observe happening. In other words, it's physics.

It may be that an entirely new explanation will be invented that will explain the fundamental difference between the two kinds of electric charge. It may have already been invented, but not yet adopted into the mainstream because there are other explanations and no one yet knows which one to adopt because they make different predictions about how Nature behaves and we don't yet have experimental or observational evidence that will tell us which one to adopt.

 

[Nugatory]

This is where you lost me, how can undividable particles, like quarks, be fractionally charged? It's the smallest of the smallest, point particles, fundamental particles, just like bits in a byte (a bit means ON or OFF, 1 of 0, + or -), so how can you argue that a 2/3 charged particle can be a fundamental (undividable) particle?

The fractional charge of the quarks is an accident of the units we use to measure electric charge. If we used other units the quark charges would come out integers.

I think that this doesn't prove that they are to be considered fundamental until proven differently, but rather the other way around.

Every measurement and every experiment we've ever done supports the claim that certain particles are fundamental. With all the evidence pointing in one direction, it makes sense to go that way until proven otherwise.

Please do remember and respect the Physics Forums guidelines:

Our mission is to provide a place for people (whether students, professional scientists, or others interested in science) to learn and discuss science as it is currently generally understood and practiced by the professional scientific community.

 

[Drakkith]

This is where you lost me, how can undividable particles, like quarks, be fractionally charged? It's the smallest of the smallest, point particles, fundamental particles, just like bits in a byte (a bit means ON or OFF, 1 of 0, + or -), so how can you argue that a 2/3 charged particle can be a fundamental (undividable) particle?

Because nature did not assign a fractional charge to quarks. We did, when we chose to keep our units based on the charge of the electron, such that 1 is the magnitude of the charge. Had we chose to modify our units when we discovered quarks, we could label them as -1 and +2 instead of -1/3 and +2/3. The electron would then have a charge of -3.

And what's wrong with fractional charge? In SI units, the elementary charge (charge of an electron/proton) is about ±1.602x10^-19 C. That's one heck of a fraction. The only time the charge of an electron or proton is not fractional is when we use a system of units where they are defined to be 1.

I think that this doesn't prove that they are to be considered fundamental until proven differently, but rather the other way around.

Science does not deal with proof. All theories are subject to continuous peer review and can be modified or tossed into the trash whenever a more accurate theory comes along. Even the existence of subatomic particles is not proven. A better theory could come along in the future and show that we are mistaken.

So that means that a photon must have some kind of dualistic characteristic, because it's able to divide.

No, that is not what it means. Or, rather, that is not what current theory says. See below.

That's why I think that the fundamental particles can't all be fundamental, in contrast with what you're saying. Maybe Planck length/charge/volume particles exist, 1 dimensional "strings", just like string theory predicts, because there's no shorter length than Planck length. Maybe the current ability of human kind is not able to detect, measure and prove it, but we might however logically deduct it with 100% certainty, the same way we logically concluded that dark matter exists.

There is almost certainly a shorter length than the Planck length. The Planck length just represents the hypothetical limit of our ability to predict phenomena. In other words, we might not be able to ever know what is occurring below that scale.

Besides that, please note that PF exists to teach people about mainstream science, not to discuss personal theories or speculation about what "might" be. You are certainly free to believe that our current theories are not the absolute truth about what is happening in the universe, and many scientists take that same view, but please limit any discussion to what we already know or can be reasonably sure about using current theories.

 

[mark!]

@Drakkith The headache I get from the definition of a fundamental particle is based on the fact that it's said that they're pointlike particles, which means that they don't consist of smaller constituents inside of them... but are however different? If quarks are pointlike, and electrons are also pointlike, than how is it possible that those two points could have different characteristics (like mass, charge and spin)?

Or take photons and gluons, how is it possible for two massless particles to NOT be the exact same thing?

Bits in a byte, they are fundamental because they're all exactly the same. No headache at all. I guess I'm misinterpreting the meaning of the word 'fundamental'.

 

[Vanadium 50]

I guess I'm misinterpreting the meaning of the word 'fundamental'.

No, but you're creating your own mental model of how the universe works, and are unhappy that nature isn't following that. There's really no reason why it should.

 

[Mister T]

@Drakkith The headache I get from the definition of a fundamental particle is based on the fact that it's said that they're pointlike particles, which means that they don't consist of smaller constituents inside of them... but are however different? If quarks are pointlike, and electrons are also pointlike, than how is it possible that those two points could have different characteristics (like mass, charge and spin)?

Because they are not points! We call them particles, but perhaps it would be better to start off thinking of them as something else, something completely unknown. Then, to get to know them start measuring some of their properties. You measure their charge, their spin, and their mass. Then you try to measure their size. According to your best technology you determine that if they have a size then it's less than about $10^{-18}$ meters, because that's the limit of your ability to measure size.

From that you infer that their size is zero, so you christen them "point particles" and declare them to be "fundamental particles" because if they have an internal structure you're unable to determine it.

They could have a nonzero size, but to the best of our ability we're unable to measure their size. This is the case with all scientific knowledge. All we know is what we're able to measure, and since we're limited in our ability to measure anything all of our scientific knowledge comes with the caveat "to the best of our knowledge". So, to the best of our knowledge, they're point particles.

It would get really tiresome adding that caveat every time we declare something. Like, to best of our knowledge, it takes 2 hours to drive to grandma's house. Or, to the best of our knowledge, electrons and protons have equal but opposite charges. To the best of our knowledge table salt is sodium chloride.

 

[Drakkith]

@Drakkith The headache I get from the definition of a fundamental particle is based on the fact that it's said that they're pointlike particles, which means that they don't consist of smaller constituents inside of them... but are however different? If quarks are pointlike, and electrons are also pointlike, than how is it possible that those two points could have different characteristics (like mass, charge and spin)?

Or take photons and gluons, how is it possible for two massless particles to NOT be the exact same thing?

Bits in a byte, they are fundamental because they're all exactly the same. No headache at all. I guess I'm misinterpreting the meaning of the word 'fundamental'.

As far as I understand things, they are called point-like because you can localize their position down to any arbitrary scale (with a corresponding uncertainty in their momentum), while they're called elementary or fundamental because they are not known to be composed of any other particles. This doesn't require that they all have the same properties.

As for how two massless particles can be different, I can't answer except to say that that's just how nature appears to work. Is it any more strange that particles with mass can be different? Why do not all particles with mass have the same mass, or perhaps an integer number of mass units (or rather that the mass of heavier particles be some integer multiple of the mass of the lighter particles)? Some questions just can't be answered at this time, and some may never be answered.