Why Is Gravity the Weakest Force?

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.

Comments

Hype

[Anonymous Coward]

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.

Re:Hype

[Beck_Neard]

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.

Re:Hype

[greenfruitsalad]

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.

Re:Hype

[InterGuru]

I thought the cost of the LHC was insanely expensive, then I realized we spent more to bail out one sleazy bank ( while the banksters still got huge bonuses. )

It has to be

[Waffle Iron]

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.

Re:It has to be

[tomxor]

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.

Re:It has to be

[ByteSlicer]

It doesn't really make sense to compare the fundamental forces that way. Only the electromagnetic field and gravity propagate far enough to exhibit an inverse square law. This is simply because the field covers a bigger spherical area at larger distances.

The strong force stays roughly constant at growing distances. This is because the color field absorbs the energy used to separate the quarks, and interacts with itself via the color force (generating virtual gluons and quarks). When the separation gets too large (i.e. sub atomic distances), the field energy condenses into new quarks close to the original quarks, and the field between the original quarks disappears (almost, but not completely. The leakage makes nucleons stick together).

The weak force is even harder to describe in this way, since it doesn't really behave like a classical force.

So how do physicists compare these forces then? Each force is associated with a quantum field, and each field has some probability to interact with some particles. This probability is a constant number called a coupling constant, and can be determined by experiment. The fact that C14 has a certain half-life for example is caused by the weak interaction having some probability of turning a neutron in a proton (by changing the flavor of one of its quarks).

So it's the value of the coupling constants that determines the strength of the force, and on average the many quantum interactions between a field (or the bosons that are its quanta) and other particles (which are also just quanta of a field) manifest as a classical force that exhibits an inverse square law.

Re:It has to be

[ByteSlicer]

No, I really meant constant, not linear. It is indeed odd, and known as color confinement.
But this property only exists at very small distances (sub atomic, nucleus scale), because once the field energy becomes too high with bigger distance, the energy is converted to mass, and these new quarks close the distance.
Outside the nucleus, the color field strength (and thus the strong force) is almost zero, because the colored quarks and gluons in the nucleus have a neutral color charge on average, similar to how positive and negative charges almost completely cancel each other out.

forbes = ad hell

[ljw1004]

I tried reading that article on my mobile device (doesn't support ad-blocker). Got ten ads. The first was a full-screen block that, after I clicked through, didn't even take me to the article. The other 9 all caused the article to "repaginate" under my fingers when I reached them (or at least, recalculate vertical spacing) and all blocked further text until they'd spent their 1-2 seconds loading.

What a terrible experience. So sure that I never got to the actual substance of the article before I gave up.

Oh, also a permanent title bar that takes too much of my small device's limited screen real estate.

Forbes is a disaster on mobile.

Broken Link

[allo]

Redirects to forbes.com/welcome, which is an empty page.

Stop linking sources with crude javascript, please.

Re:I'll tell you why

[Aighearach]

Physics can only predict the future, it can't tell you why anything happens. Only what happens, and when.

It's not *that* much of a mystery...

[rocket rancher]

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?"

Try Other Questions

[VernonNemitz]

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.