# What causes electric charge **URL:** \ **Category:** Factual Questions\ **Created:** [October 4, 2004, 4:02pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472 "2004-10-04T16:02:21Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [October 4, 2004, 4:02pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/1 "2004-10-04T16:02:21Z")
What is the basis for the positive charge in protons and the negative charge in electrons? Has anyone figured that out yet? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [October 4, 2004, 4:18pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/2 "2004-10-04T16:18:23Z")
It’s an intrinsic property, and can’t be said to be “caused” by anything, although it should be noted that an electron is an elemetary particle (can’t be broken down further) while a proton consists of 2 up quarks and one down quark. Charge is like mass. It just is. We observe it and measure it and understand what it is, but not why it is. ---
**Author:** ![Small\_Clanger](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@Small\_Clanger](https://boards.straightdope.com/u/Small_Clanger)\ **Post date:** [October 4, 2004, 4:35pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/3 "2004-10-04T16:35:09Z")
> [@](#): > > What causes electric charge Cat hair? > [@](#): > > Charge is like mass Mass isn’t quantised, but otherwise I agree. The charge on an electron is a quanta (I hope that’s the right word) of the electric field. The electric (better: electro-magnetic\*\*\*\*\*) field is a property of space. Mass is to gravity as charge is to the electric field. Steps back and waits for a physicist to step in and destroy my description. \*\*\*\*\*Or even electro-magnetic-weak field ---
**Author:** ![Fuji\_Kitakyusho](https://avatars.discourse-cdn.com/v4/letter/f/f0a364/32.png) [@Fuji\_Kitakyusho](https://boards.straightdope.com/u/Fuji_Kitakyusho)\ **Post date:** [October 4, 2004, 4:53pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/4 "2004-10-04T16:53:45Z")
Not necessarily adding anything explanatory to the discussion, but my understanding is that a proton, carrying a charge of 1e+ consists of three quarks which have +2/3, +2/3 and -1/3 charge (2 up and one down), while a neutron also consists of three quarks, but since the neutron has two down and one up (-1/3, -1/3, +2/3) its charge is zero. The electron carries a charge of 1e-, and is not composed of smaller particles, AFAIK. Does this make sense? ---
**Author:** ![Complex\_Conjugate](https://avatars.discourse-cdn.com/v4/letter/c/3bc359/32.png) [@Complex\_Conjugate](https://boards.straightdope.com/u/Complex_Conjugate)\ **Post date:** [October 4, 2004, 4:53pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/5 "2004-10-04T16:53:53Z")
‘Postive’ and ‘negtaive’ charge are merely conventions, so it’s simply an accidne tof history that electrons are negatively charged and protons postively charged, the actual property is that they are oppositely charged. In the standard model, the electric charge of a particle is dependent on it’s hypercharge and weak isospin. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [October 4, 2004, 5:21pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/6 "2004-10-04T17:21:24Z")
> [@Small Clanger](#): > > Mass isn’t quantised, but otherwise I agree. I was going to say “good point”, but then I thought that mass actually is quantized since you can only construct matter from elementary particles. You can’t have mass less than the least massive particle (I don’t remember which one that is). > [@](#): > > The charge on an electron is a quanta (I hope that’s the right word) of the electric field. The electric (better: electro-magnetic\*\*\*\*\*) field is a property of space. a quant **um**. The EM fileld isn’t a property of sapce-- it’s a property of whatever charge happens to exist. Actually, gravity can be said to be a property of space-time, where mass distorts the space around it. The EM/gravity analogy is not a bad one, as long as you don’t take it too far. For example, a magnetic field is created by a moving charge. But a moving mass does not create an analogous effect. ---
**Author:** ![Complex\_Conjugate](https://avatars.discourse-cdn.com/v4/letter/c/3bc359/32.png) [@Complex\_Conjugate](https://boards.straightdope.com/u/Complex_Conjugate)\ **Post date:** [October 4, 2004, 6:03pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/7 "2004-10-04T18:03:31Z")
> [@John Mace](#): > > I was going to say “good point”, but then I thought that mass actually is quantized since you can only construct matter from elementary particles. You can’t have mass less than the least massive particle (I don’t remember which one that is). Mass isn’t quantized as far as anyone knows, but it may very well be. The least massive particles are obviously those particles of zero mass, the least massive massive particle is the electron neutrino I guess (presuming it does have mass). But the stating that mass is quantized is alot stronger than staing that there is a particle of lowest mass. > [@](#): > > The EM/gravity analogy is not a bad one, as long as you don’t take it too far. For example, a magnetic field is created by a moving charge. But a moving mass does not create an analogous effect. Intersetingly in general relativity there is something analgous to magnetsim in elctromagnetism, it is called gravitomagnetsim or frame-dragging. Nasa’s Gravity Probe B is currently trying to observe this effect. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [October 4, 2004, 6:43pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/8 "2004-10-04T18:43:42Z")
> [@Complex Conjugate](#): > > Mass isn’t quantized as far as anyone knows, but it may very well be. The least massive particles are obviously those particles of zero mass, the least massive massive particle is the electron neutrino I guess (presuming it does have mass). But the stating that mass is quantized is alot stronger than staing that there is a particle of lowest mass… But the least charged particle is one with zero charge. Mass may be multiply quantized in that there are different elemetary particles with different masses, but that is very different than saying you can create any arbitrary mass by assembling different particles. You can’t. ---
**Author:** ![biqu](https://avatars.discourse-cdn.com/v4/letter/b/7feea3/32.png) [@biqu](https://boards.straightdope.com/u/biqu)\ **Post date:** [October 4, 2004, 7:45pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/9 "2004-10-04T19:45:03Z")
> [@Wesley Clark](#): > > What is the basis for the positive charge in protons and the negative charge in electrons? Has anyone figured that out yet? A quantum electrodynamicist might say that electrical charge results from the exchange of virtual photons. ---
**Author:** ![Complex\_Conjugate](https://avatars.discourse-cdn.com/v4/letter/c/3bc359/32.png) [@Complex\_Conjugate](https://boards.straightdope.com/u/Complex_Conjugate)\ **Post date:** [October 4, 2004, 7:55pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/10 "2004-10-04T19:55:07Z")
> [@John Mace](#): > > But the least charged particle is one with zero charge. Mass may be multiply quantized in that there are different elemetary particles with different masses, but that is very different than saying you can create any arbitrary mass by assembling different particles. You can’t. You can argue that particles are quantums of mass, but that would not be it’s usual meaning. Also the mass of a system of particles is not depenednt on their individual masses only. ---
**Author:** ![JasonFin](https://avatars.discourse-cdn.com/v4/letter/j/4af34b/32.png) [@JasonFin](https://boards.straightdope.com/u/JasonFin)\ **Post date:** [October 4, 2004, 8:04pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/11 "2004-10-04T20:04:48Z")
> [@John Mace](#): > > But the least charged particle is one with zero charge. Mass may be multiply quantized in that there are different elemetary particles with different masses, but that is very different than saying you can create any arbitrary mass by assembling different particles. You can’t. You’re forgetting E=mc^2. In most cases, the kinetic energy a particle has can take on any level whatsoever. Technically, an object’s mass is its mass, or its energy divided by c^2 (same thing), in the inertial reference frame in which it has no momentum. (This doesn’t quite work for zero-mass particles because they travel at c and so have nonzero momentum in every frame. However, their energy can be measured to be arbitrarily small in some frame). This means that a system of two photons traveling towards one another can have any mass whatsoever. Mass isn’t always additive in relativity, so it’s okay that each individual photon is massless. That is kind of cheating, though. Every stable bound system in quantum mechanics has quantized energy, so it’s probably true that only discrete masses are possible for stable macroscopic objects. Only unstable systems can have unquantized kinetic energy that contributes to their mass. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [October 4, 2004, 8:14pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/12 "2004-10-04T20:14:55Z")
> [@JasonFin](#): > > That is kind of cheating, though. Every stable bound system in quantum mechanics has quantized energy, so it’s probably true that only discrete masses are possible for stable macroscopic objects. Only unstable systems can have unquantized kinetic energy that contributes to their mass. Accodring to [this paper (PDF),](http://arxiv.org/PS_cache/gr-qc/pdf/0309/0309100.pdf) mass is quantized. ---
**Author:** ![Complex\_Conjugate](https://avatars.discourse-cdn.com/v4/letter/c/3bc359/32.png) [@Complex\_Conjugate](https://boards.straightdope.com/u/Complex_Conjugate)\ **Post date:** [October 4, 2004, 8:51pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/13 "2004-10-04T20:51:52Z")
> [@John Mace](#): > > Accodring to [this paper (PDF),](http://arxiv.org/PS_cache/gr-qc/pdf/0309/0309100.pdf) mass is quantized. That paper is speculative, it relies on untested theories and principles. ---
**Author:** ![Loopydude](https://avatars.discourse-cdn.com/v4/letter/l/e56c9b/32.png) [@Loopydude](https://boards.straightdope.com/u/Loopydude)\ **Post date:** [October 4, 2004, 9:54pm UTC](https://boards.straightdope.com/t/what-causes-electric-charge/267472/14 "2004-10-04T21:54:27Z")
My understanding from my limited knowledge of QED is that electric “charge” is a function of the likelihood a particle will emit or absorb a virtual photon. For an electron, muon, or tau, for instance (at sufficiently low energies), that likelihood is related to the value of the electrical coupling constant (a.k.a. the “fine structure constant”), approximately 1/137. When a particle absorbs or emits a photon, it recoils with a momentum relative to the energy of said photon. Two electrons, with opposite charge, could be thought of as being bombarded by virtual photons emitted from either electron, pushing them apart. It’s a little more complicated with, say, an electron and a positron; one can think of the particles aborbing and emitting photons between them that sort of knock them toward one another; or you could think of them as absorbing photons from the opposite direction out of the vacuum, giving them motion towards one another. One analogy I’ve read about is to imagine two electrons being like two ships that shoot cannon balls at one another, alternately recoiling from the cannon blast or the impact of the ball. In the case of an electron and a positron, one could think of them being like two ships hurling boomerangs at one another, such that the boomerang circles around behind the target ship, striking it, and pushing it towards the other ship. The latter analogy is kind of weak, IMO, and I’m still waiting for a better analogy to describe the phenomenon of the motion of unlike charges toward one another.