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Why Is Gravity the Weakest Force?

Posted by timothy on from the maybe-it's-just-biding-its-time dept.

StartsWithABang writes: If you calculate the forces between two fundamental particles separated by subatomic distances, you find that the strong, electromagnetic or weak nuclear force could all be the strongest, dependent on the particulars of your setup. But throw gravity in there, and it turns out to be weaker by some 40 orders of magnitude. This discrepancy, that gravity is such an oddball, is known as the hierarchy problem, and is by many measures the greatest unsolved problem in theoretical physics. Yet the new, upgraded run of the LHC has the potential to uncover any one of four possible solutions, some of which we have hints for already.

9 of 207 comments (clear)

  1. Hype by Anonymous Coward · · Score: 4, Interesting

    Theoretical particle physicist here. These claims are hype. Pure wishful speculation to entice funding agencies via the general public. They should be ashamed of themselves. Best to ignore them. Cui Bono.

    1. Re:Hype by Beck_Neard · · Score: 4, Interesting

      To be fair to them, it's a very tough time for fundamental physics right now. Progress is insanely expensive, funding is all but non-existent, it's hard to find talented scientists who actually want to study it, and the general public just isn't interested anymore.

      --
      A fool and his hard drive are soon parted.
    2. Re:Hype by greenfruitsalad · · Score: 4, Interesting

      i disagree with the part about talented scientists. there are plenty of theoretical scientists in physics but nothing for them to do (funding problem). the brightest 0.1% get a job in their field, 1% stay at their university for life, the rest sell used cars or teach high school physics.

      i know a guy how knows a guy... who worked at LHC and i heard about how the jobs dried up during the hiatus. theoretical physics is not a field i'd study if i wanted a safe career.

    3. Re:Hype by Dcnjoe60 · · Score: 3, Interesting

      To be fair to them, it's a very tough time for fundamental physics right now. Progress is insanely expensive, funding is all but non-existent, it's hard to find talented scientists who actually want to study it, and the general public just isn't interested anymore.

      There is a reason for this. There isn't a lot of practical application from theoretical physics, particularly given the high cost. Businesses realize this, which is why they don't invest in such research and it is left up to the government. In a time of anti-government spending, no ROI equates to no funding.

      As for the general public not being interested, there is, in the USA, anyway, a strong correlation between the decline of the middle class and funding of science. Why? The rich don't need it and the poor are too busy trying to figure out how to get their own basic needs met. In addition, tax revenues, which fund such endeavors come from a strong economy. Economists will tell you that the economy is driven by the middle class. A strong middle class equates to a strong economy and vice-versa.

      So, in short, yes, the public doesn't care about any of this, because the public is interested in either accumulating more wealth or meeting basic needs. Doing something for the common good has gone the way of the middle class.

  2. It has to be by Waffle+Iron · · Score: 5, Interesting

    Unlike the other three forces, gravity neither cancels out because of negative and positive versions, nor peters out beyond subatomic distances. Its effects are therefore cumulative over huge swaths of the universe.

    If gravity were much stronger, the entire universe would collapse into a singularity, and we wouldn't be here to gaze at our navels about the issue.

    1. Re:It has to be by tomxor · · Score: 5, Interesting

      If the force of gravity is the inverse square of the distance, what are the 'powers' of the other forces? Cubed, quad power, 10th power?

      I always had roughly the same thoughts on this argument, that other fundamental forces don't appear to operate over the distances that gravity does... but it's actually quite logical when you play out the details: The inverse square function of distance is no coincidence, it's comes from the dimensionality of space and an omnidirectional force which is why it applies to other things like electromagnetic waves.

      Other forces are stronger (the strong nuclear force is 10^38 times stronger than gravity at the same distance!) and i think they probably have the same distance function... So why isn't it stronger at large distances? As others have said the main difference between gravity and other forces is it's insatiability, (it's cumulative). When some subatomic particles form an atom, the forces at play are satisfied to some degree and the resulting matter is less reactive (has less attraction to other similar matter); whereas when matter coalesces under the force of gravity, only separation is satisfied, the force is just combines resulting in a denser gravitational force in a region of space.

      Another way to compare is by imagining under what hypothetical scenario another force would act the same way: for instance how could you make a strong nuclear force on a universal scale, you would need a large mass (i.e the size of the earth) of protons or something... and they need to stay in the same place (not fly apart) oh and they need to have not reacted with anything... That scenario would result in a frighteningly large force but it will also never happen because those forces tend to get satisfied on small scales very quickly.

  3. ... And time is the strongest dimension by wylderide · · Score: 3, Interesting

    We are dragged along by four dimensions as they expand, but we can still move freely in the other three, but not time. Coincidence? Yeah, probably, but maybe not.

    --
    This is the best restaurant I ever eat in
  4. It's not *that* much of a mystery... by rocket+rancher · · Score: 4, Interesting

    if you think about it for a moment in terms of the weak anthropic principle, gravity has to be very weak, because it is cumulative. The Weyl curvature of spacetime, which is the metric tensor that governs the propagation of gravity in free space, acts across the entire Einstein manifold, i.e., everywhere at the same time. If gravity were any stronger, it is pretty unlikely that matter as we understand it would be able to exist long enough to produce objects like humans capable of asking that question.

    With that said, it is not really an important question question on its own, as the over-hyped intro suggests. The important questions pretty much are looking for explanations as to why the universe behaves so differently at different scales and velocities. Important questions in physics and cosmology are more along the lines of "Why are our two most successful theories about the nature of the universe, quantum mechanics and general relativity, incompatible with each other?"

  5. Try Other Questions by VernonNemitz · · Score: 4, Interesting

    We know the theorists want to be able to describe gravitation in terms of Quantum Mechanics. This will necessarily involve hypothetical "virtual gravitons" as "exchange particles" between interacting masses. So:
    How do gravitons, even virtual ones, escape a black hole?
    How do gravitons from the Sun pass through the Earth to affect the Moon (and artificial satellites) when eclipsed by the Earth, as if the Earth was a zero-size object? That is, the orbits of those bodies don't change just because the Earth sometimes eclipses them from the Sun's perspective.
    In a way, just one proposal can answer both those questions, plus the one in the title of this page's article. If gravitons interact very rarely with other particles, including each other, then they can't stop each other from escaping a black hole, the Earth would be mostly transparent to them --AND gravitation would be the weakest force.