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Fundamental Forces Questions

  1. Feb 21, 2008 #1
    IDK if my understanding is right...but as far as I understand physics...all the fundament forces shares 2 characteristics - attraction and repulsion....now, here are my questions..

    1. Assume there are only 2 uncharged atoms in the universe.....would they come together or go apart or stay where they are?

    2. If there were two atoms w/ such charges that they repelled, would they travel apart forever or would they slow down at such a rate that there would be an asymptote?

    3. If they were attracted to each other, would they only stick together or would they become one?(what is the force that is keeping them apart?) Since everything in the universe tries to establish equalibrium...should those 2 atoms be equally distributed by first unifying then distributing?

    Thank you.
  2. jcsd
  3. Feb 21, 2008 #2
    I think that the above questions are fundamental in nature and requires nothing more than the knowledge of fundamental physics.

    1. The law of gravitation is by far attractive in nature (though I have read some articles that describe its repulsive nature but that is our cup of tea right now). Therefore I can confidently say that the two masses would eventually come together(given the above conditions).

    2. Charges of same nature always repell each other. Therefore the two particles would travell away from each other at a rate that would slow down asymptotically.

    3. The outer portion of atoms contains negatively charged electrons. Therefore they would not become one due to the electron repulsion.
    Last edited: Feb 21, 2008
  4. Feb 21, 2008 #3


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    For 2.) I would think that they would repel and eventually stay stationary relative to each other due to the balance of gravity and EM. But on an atomic scale it's a different question, surely uncertainty would make a dog's breakfast out of that? You would know their exact positions at a certain time.
  5. Feb 21, 2008 #4

    Andy Resnick

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    You raise an interesting question. I'm not sure there's a clean answer. The origin of the difficulty lies in the fact that you removed a clear reference frame- the fixed stars, for example. On the other hand, you do have a reference plane- that plane containing the two particles.

    Mach's principle would seem to imply that what happens is indeterminate. You cannot unequivocably measure the rotational inertia within the plane. There is an effect called the "Lense-Thirring effect", or "frame dragging" which was verified recently by Gravity Probe B, but that holds for single rotating particles....

    I'd be interested to read other responses....
  6. Feb 21, 2008 #5
    1. Atoms would be attracted (gravitation), unless they were already so close (about the diameter of atom) that the repulsion of electrons is stronger.

    2. The atoms would fly away from each other. the speed would not aproach to zero, but to a constant determined by initial electrostatic energy and mass of atoms.

    3. Because of electron-electron forces they would either bounce away or form a molecule
    (if something forced them together in the beginning).

    I assumed the initial velocity dr/dt(0) was 0 and that the line formed by the atoms was not rotating. Since we only have 2 points, we don't immediately see the perpendicular component of speed, so we can't really check for rotation of our coordinate system unless we wait some time to see if the Newton's law can explain the movement without introducing system forces (caused by acceleration of coordinate system).
    Last edited: Feb 21, 2008
  7. Feb 22, 2008 #6
    Nice....but what would happen when the atom starts aging and nuclear decay comes into affect?
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