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Gravity as a resultant force?

  1. Feb 11, 2010 #1
    If gravity is miniscule compared to the other three interactions, could it be a kind of resultant 'force' left over from balancing the strong, weak and electromagnetic interactions? One which is then much more detectable on the larger scale, when all these tiny gravitational forces from each atom combine.
    Is this a 'high school' over simplification and if so, where do I start to unravel this mystery?
  2. jcsd
  3. Feb 11, 2010 #2


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    Note that 1) it is additive, the more mass you put, the more strong the force is. And 2) it goes as the inverse square. Such properties are not typical of residual forces.

    Said that, the study of residual forces is interesting. Van der Waals etc. Also, in some sense you could look at tidal force as a residual, as it appears after you have substracted the "point-like body" gravity.
  4. Feb 13, 2010 #3
    Thanks for the help on this one!! Is it possible to detect gravity at the scale of individual atoms? So, would you be able measure it for (let's say) one atom of carbon and then for a known number in an allotrope like graphite? Would the measurement be directly proportional to the number of atoms you had? Or, are we talking about something that as yet can't be measured at this scale?
  5. Feb 13, 2010 #4


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    Last edited by a moderator: Apr 24, 2017
  6. Feb 13, 2010 #5
    The earth's gravitational field can be detected by observing it's affect on an individual atom (the links provided by ZapperZ), but the gravitational field that an individual atom produces cannot be detected. The former is called the passive gravitational mass of the atom and the latter is called the active gravitational mass of the atom. The active force of gravity is far too weak to measure at this scale. You can use Newton's universal law of gravitation to calculate it.
    Last edited: Feb 13, 2010
  7. Feb 13, 2010 #6
    Theoretically it would be possible to detect the gravitation between individual atoms, but not practically. Our instruments are nowhere near that sensitive and precise.

    And no, the mass of a compound is different than the sum of the masses of its component atoms, because there is some mass defect due to the chemical bonds. This is because mass is not conserved, it is an artifact of something else. We don't really understand much about this.
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