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Human No More?

The Mysterious Force Called Gravity

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by , 11-12-2010 at 11:39 AM (2522 Views)
Ok, no philosophy this time. I have a real physics question that's been bugging me for a while, and I can't seem to find any answers to help give me a clear understanding of the situation. I think I have a basic idea, but don't know if I'm at least on the right track or not. I've heard different hypothesis regarding gravity, and just what it is exactly. At this point I get the classical physics idea of it being associated with the curvature of space due to mass. I also realize that it can affect and bend light around objects like stars. The thing I'm having problems with is if it should be as strong as say the electromagnetic force, then why isn't it? I heard recently that what we experience as gravity on our level is actually a "bleed through" effect from a deeper level or dimension of reality? This would explain why it appears to be weaker than electromagnetism when it shouldn't be. If this is true then does it still operate on the premise that it's the result of the curvature of space around mass? Does this mean that this hidden or inner dimension is somehow more dense or massive than our own physical universe? And what part does dark matter and energy play in it all, if any? I would appreciate any insights from professionals and laymen alike.
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  1. Drew Bynum's Avatar
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    Gravity, at least on this planet, is the weakest possible force that we know of, as well as experience. Dark Matter is thought to be the invisible scaffolding (and somehow shouldn't exist, but has to) that is holding all of the billions of galaxies across the universe together. We call it 'dark', because we have had to actually 'add' extra gravity to explain why galaxies don't actually fly apart (in simulations that calculate the mass of galaxies) - I wish I had a better answer to your question, but as an ameteur, I can only simply regurgitate what I have learned over the years. This is, however, a realllllyyy good question!
  2. artmark's Avatar
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    The simple answer here is that gravity IS by far the weakest of the 4 primary forces, not just here on earth, Drew, but everywhere in the universe. There is no reason it "should" be as strong as the electromagnetic force.
    The reason it is the primary force we experience as human beings has to do with the fact that we know of no other countervailing force, and because its effect diminishes with distance via the inverse square law, but never completely vanishes.
    In comparison, the electromagnetic force is the result of a preponderance of particles of one charge, positive or negative. However, as the level of charge in any large conglomerate of matter (say a planet) will tend to equal out, it has limited net effects in the universe at large, even though it is constrained by the same inverse square law. The strong and weak nuclear forces only operate on extremely small sub atomic scales within the nucleus of the atom. While these forces are far stronger, they do not propagate into the large scale structure of the universe. Of course, without them, there would be no matter, as they make it possible for the nucleus of the atom to exist rather than flying apart (remember that the nucleus is all positrons and neutrons, and would otherwise fly apart as positive charged particles repel each other).

    Gravity, on the other hand, though weak, can continue to build on itself without limit. It operates over infinite distances. With sufficient mass concentrated in a sufficiently small area, its net effect will first overwhelm the electromagnetic force, crushing the electron shells into their nucleus where the negatively charged electrons "short out" the positively charged positrons in the nucleus. In stellar terms this breakdown results in a neutron star. However if there is more mass, or more acquired, gravity builds until it breaks down the strong nuclear force as well. In this case, the star collapses to a singularity, with all the mass compressed to an infinitely small and dense spot. And we have a classic black hole. Gravity pulls the light back in too.

    Hope this helps. Isaac Asimov wrote a wonderful primer on this called "The Collapsing Universe". The science in some of it is a bit out of date, but this particular information is still completely relavent and much better stated there.