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Why are small particles always spherical ?

  1. Feb 5, 2012 #1
    particles like protons and maybe photons, they are always spherical why? do they create a gravitational field?
     
  2. jcsd
  3. Feb 5, 2012 #2
    Who said they were? Photons aren't really particles, though, and if they are, they are points, rather than spheres.
     
  4. Feb 5, 2012 #3
    I think they are drawn spherically just so we have something to picture. Remember that protons are actually made up of quarks so they probably aren't spherical, it's a simplification.
     
  5. Feb 5, 2012 #4

    Pengwuino

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    This basically sums it up. They're drawn as spherical objects because that's a convenient way to learn about them. When I draw a car for an example on kinematic motion, I would probably just draw a box with a couple of circles underneath. The shape is inconsequential. The idea is the same for things like photons and protons (although I never do see photons as spheres). The shape isn't important in examples where people are typically drawing protons.

    The true nature of things like protons, photons, and electrons are not easily drawn and could possibly be misleading, so just showing them as little spheres is as far as most people care to go and is a very good approximation for a vast majority of applications.

    They also do gravitate, but their gravitational fields are so weak that no one ever mentions them on a particle-by-particle basis. The fact that they gravitate has nothing to do with the fact that they're approximately spherical, though.

    This is not true at all. Photons are best described as traveling waves.
     
  6. Feb 5, 2012 #5

    DaveC426913

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    While subatomic particles do not have a dimensions (they are point objects), their influences (charge) do have dimensions (a proton has a charge of X at a specific distance Y), and the shape of this influence is spherical - it has no special orientation, having the same value at distance Y along any axis.

    A sphere is symmetrical about all axes, just like a particle's field.

    Choosing any other shape would add an asymmetry to the symbol. Use a square, cube or tetrahedron for the symbol and suddenly you have an implied orientation. (Why is this photon on its square face and that photon on its point?)
     
  7. Feb 5, 2012 #6

    DaveC426913

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    This is not true at all that this is not true at all.

    Photons are best described as whichever model (particle or wave) best suits the need at-hand. Sometimes it makes more sense to imagine a photon as a particle. And considering the OP's question, clearly he is asking about examples where they are described or illustrated as particles.
     
  8. Feb 6, 2012 #7
    That's why I said "photons are not really particles, though".
     
  9. Feb 6, 2012 #8

    Pengwuino

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    Sure, it can be more convenient that talking about them as point-like objects but this doesn't make it true. The proton is not a point-like object, but when it will make no consequence, we consider it a point particle. With light, yes, you will treat it as point-like particles but only in a regime where treating them as such has no consequences just like doing the same with protons is an acceptable choice. I'm just saying in reality, they're not, just like protons are not point-like. Using them differently in a model is fine by me, I don't mean to take issue with that.

    I think I may have had more issue with the "light is not a particle" than whether the point-like or wave-like view of them is correct. I think point-like vs. wave-like almost becomes a moot point at the quantum level.
     
  10. Feb 6, 2012 #9

    turbo

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    Particles are not "spherical". Their influence can be inferred (simplified) to have spherical "spheres" of influence, but we lose a lot of detail with that simplification.
     
  11. Feb 7, 2012 #10
    Considering that the Heisenberg uncertainty in a particles position is typical going to be larger then the particles "physical size" I question weather physical size or shape are meaningful concepts at the quantum scale.
     
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