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Question concerning the nature of charges

  1. Apr 22, 2005 #1
    I am actually a philosophy student that is dabbling in physics, so the nature of this question may seem a bit strange. My question is regarding whether electromagnetic charges are disjunctive in nature. In case you are not familiar with the philosophy lingo, a disjunctive property is one in which the underlying physical properties seem to have nothing that really unifies them, but the macro features all fit into a single category. For example, redness is often called a disjunctive property because the underlying physical properties of red objects are all so different. It has been suggested that charge is an example of such a disjunctive property.
    What I am wondering is if charge has any underlying physical nature such that both positive and negative charges really have something deeply in common, at least according to some accepted theories. I know that protons are made up of quarks, and that electrons are a type of lepton, and that protons are vastly larger than electrons, so the charges seem do seem, at least on the surface, very different in nature. I know that mathematically the charge on an electron needs to balance out the charge on a proton, and that when a neutron decays it emits a proton and an electron and an antineutrino. Is there anything in all this that suggests that there is an underlying physical property that the charges might share?

    As I was trying to find an answer I ran across an article published in the General Science Journal at http://www.wbabin.net/physics/albertini.htm that seemed to suggest that according to superstring theory (or subquantium theory?) that, at least for magnetism, both positive and negative charges might be caused by space-time wave functions in different phases (see the illusion of magnetism section). Is this an accepted theory, and if so could it also be applied to particle charges?

    Any ideas are appreciated!
  2. jcsd
  3. Apr 22, 2005 #2

    Andrew Mason

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    It only appears disjunctive until you are able to identify the reason red objects are red. All red objects have a common property: they absorb blue and yellow light and reflect the red.

    If it appears disjunctive, it may because we don't know enough about it.

    It seems to me that disjunctiveness is a function of our state of knowledge rather than physics.

  4. Apr 24, 2005 #3
    I am not an advocate of disjunctive properties myself, but what you suggested about colors is incorrect. Color vision is very complex. The eyes are setup in two opponent pairs. The red-green (R-G) pair and the blue-yellow (B-Y) pair. R-G is the primary opponent system, and B-Y is secondary, and the two are connected. Whenever red is is stimulated, yellow actually is also stimulated, without any yellow light being present. In order to have something appear a true red, it must also have blue light present to cancel out the yellow. Seeing yellow becomes even more complex, as it is possible to see yellow when there is either yellow light or just red light and green light which balance each other out, leaving only the yellow stimulation. In addition to this, there are so many ways for any given color to occur such as simple reflection, diffraction, interference, transmission, etc. Then there are metameres, which are colors that appear to be the same in one lighting condition, but will look dissimilar under a different lighting condition, such as noon-day light and indoor lighting. A metamere can change radically in different lights, (e.g. from red to blue) and it is difficult to say when we see the "real" color of an object - is it only under noon day light? - even afternoon lighting can cause objects to look different from midday lighting. Any two objects that are red will probably have very different reflectance spectra. It really is much more complex than it initially appears. I can understand why people postulate disjunctive properties to explain colors.

    The philososphy of colors is tricky, but I really want to know about the charges of particles. I want to say that the disjunctiveness of the charges is something future science has yet to determine, but my case would be even stronger if there are at least reasonable theories floating around that postulate that there is something which is the basis for all charges.
  5. Apr 24, 2005 #4
    As you may or may not know, all measurements of charge are in terms of integer multiples of the elementary charge. That is, any charge can be written: +e, -3e, +100001e. A slightly better than circular answer to your question would be "all charges share in common that they are multiples of the elementary charge".
  6. Apr 24, 2005 #5
    So bascially you are looking for a reason or lack of reason that all charges are what they are? What makes (or does not make) all negative chargers the way they are?

    Also, your explanation of psychological colors was amazing! I have tried to explain to people time and time again that red, yellow, and blue are just pschologically primary colors and that in physics there aren't any 'primary' colors.

    What is the purpose of examining if something is disjunctive? Charges are kinda set-in-stone, according to classical physics electrons and protons just have them because that's the way they are. I'm sure quantum physics has broken it down more though.
  7. Apr 27, 2005 #6
    Basically, the purpose of examining if there are disjunctive properties in the world is because philosophers are an argumentative bunch. Disjunctive properties just don't sound like real features of the world to many of us. When a group of things are all liquid, then they all have a property in common, namely the way the molecules are moving. But if you group a watermelon and a cloud and a fish into the same category because Joe Schmo smiles every time he sees either a watermelon, a cloud or a fish, and then say that those three items share a disjunctive property, it just sounds - fishy. You can't just join random items together and then say that you have found an actual property of objects in the world. You can make disjunctive concepts like that, but they just aren’t properties. Those who advocate disjunctive properties believe that colors are an example of a disjunctive property, and now there is a suggestion that charges are a second example. If they can find more than one example of disjunctive properties, they feel their claim is on more secure ground.

    Charges seem like real properties of particles, and I am just trying to understand them more completely. There is something that seems strange about the way protons and electrons are exactly opposite charges, and yet are so very different in how they are made up. Is an elementary charge something all these particles have (do protons have something that is simply reversed or shifted on an electron? Is the charge on a positron the same as the charge on a proton?) or is it just a way of describing how the particles interact (perhaps like the hooks and loops of Velcro)? I'm not even sure if that question makes sense from a physics standpoint.
  8. Apr 27, 2005 #7


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    You cannot measure "color". However, you CAN measure and give a quantitative value to the property that CAUSE that color, i.e. frequency or wavelength of light. Even a RANGE of wavelengths that our eyes perceive to be "red".

    Electric charge is certainly quantifiable and measurable. And most importantly, the value is well-defined and reproducible. While people may argue on whether that color is "red" or "reddish" or "too red", there is no argument if a wavelength is 650 nm, or if the value of a charge is 1.602 x 10^-19 Coulombs.

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