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Gravity vs. Diffusion.

  1. Jan 2, 2004 #1
    The concept of diffusion is confusing me, as it seems to contradict gravity.

    x = particles of matter with a mass of 1
    | = a barrier particle x can permeate

    Situation A:

    (1)In my biology class, we're told, and do experiments to prove that, in this situation, the result will be:

    Result of Situation A (tested approximately)

    The explanation of this is that the particles are simply too tightly packed and want to expand.

    (2)However, Newtons law of gravity would show that the 5x's would attract the 1x with a force 5 times greater than the 1x would attract the 5x's(I think). Therefore, in order to equal out(3x's per side), wouldn't the 1x need to pull twice as hard on the 5x's? Doesn't newtons law of gravity show that the result of that experiment would tend towards the side with 5x's at least keeping all of it's particles, if not gaining the 1x?

    Oh god I'm so confused...
    Last edited: Jan 2, 2004
  2. jcsd
  3. Jan 2, 2004 #2


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    Science Advisor

    Newton's law of gravity has nothing to do with this- the gravitational pull of one small particle on another is almost nil.
    One crucial point is that the particles are all in motion (air molecules or molecules suspended in water), a little more precise than "want to expand" is that the molecules collide with each other. The closer the molecules are packed the more collisions and the more they bounce away from one another, thus "spreading out".
  4. Jan 2, 2004 #3
    If the force of such small particles upon each other is negligable:

    1.) At what approx. mass does gravity take precedence over diffusion?
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