The strength of the strong force:
Much ado was made about the Higgs boson when this elusive particle was discovered in 2012. Though it was touted as giving ordinary matter mass, interactions with the Higgs field only generate about 1 percent of ordinary mass. The other 99 percent comes from phenomena associated with the strong force, the fundamental force that binds smaller particles called quarks into larger particles called protons and neutrons that comprise the nucleus of the atoms of ordinary matter.
Now, researchers at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility have experimentally extracted the strength of the strong force, a quantity that firmly supports theories explaining how most of the mass or ordinary matter in the universe is generated.
This quantity, known as the coupling of the strong force, describes how strongly two bodies interact or "couple" under this force. Strong force coupling varies with distance between the particles affected by the force. Prior to this research, theories disagreed on how strong force coupling should behave at large distance: some predicted it should grow with distance, some that it should decrease, and some that it should become constant.
[...] They found that as distance increases between affected bodies, strong force coupling grows quickly before leveling off and becoming constant.
"There are some theories that predicted that this should be the case, but this is the first time experimentally that we actually saw this," Chen said. "This gives us detail on how the strong force, at the scale of the quarks forming protons and neutrons, actually works."
These experiments were conducted about 10 years ago, when Jefferson Lab's electron beam was capable of providing electrons at up to 6 GeV in energy (it's now capable of up to 12 GeV). The lower-energy electron beam was required to examine the strong force at these larger distances: a lower-energy probe allows access to longer time scales and, therefore, larger distances between affected particles.
[...] This means strong force coupling at large distances is important for understanding this mass generation mechanism. These results also help verify new ways to solve equations for quantum chromodynamics (QCD), the accepted theory describing the strong force.
For instance, the flattening of the strong force coupling at large distances provides evidence that physicists can apply a new, cutting-edge technique called Anti-de Sitter/Conformal Field Theory (AdS/CFT) duality. The AdS/CFT technique allows physicists to solve equations non-iteratively, which can help with strong force calculations at large distances where iterative methods fail.
[...] So, while these results were generated by experimentalists, they affect theorists the most.
[...] Only time will tell which theories these new experiments support.
Journal Reference:
Deur, Alexandre, Volker Burkert, Jian-Ping Chen, and Wolfgang Korsch. 2022. "Experimental Determination of the QCD Effective Charge αg1(Q)" Particles 5, no. 2: 171-179. https://doi.org/10.3390/particles5020015
(Score: 2) by maxwell demon on Wednesday August 10 2022, @07:55AM (16 children)
Actually I'm surprised that this question was not yet settled.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by fraxinus-tree on Wednesday August 10 2022, @08:11AM
Same here. Looks like it is somewhat more settled now. It is yet to be confirmed by different experimental method.
(Score: 3, Funny) by Thexalon on Wednesday August 10 2022, @10:43AM
They were just being careful. After all, as a wise man once said, never underestimate the power of the strong force.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 5, Insightful) by Immerman on Wednesday August 10 2022, @01:07PM (13 children)
I'm not so surprised - you're talking about determining the long distance force between "particles" that can't exist separately from each other.
I'm actually quite curious about how exactly they measured it - beyond the fact that it somehow involved a polarized beam of electrons interacting with both protons and neutrons.
(Score: 3, Interesting) by gznork26 on Wednesday August 10 2022, @04:18PM (12 children)
Does anyone here know whether theorists have worked out if the strong force causes any warping of space-time? If it did, even a tiny bit, then perhaps a large agglomeration of such tiny warping could yield gravitation.
(Score: 5, Informative) by Immerman on Wednesday August 10 2022, @08:09PM (11 children)
It stores energy, so it absolutely does. In fact that's where about 99% of the identified mass of the universe comes from.
A proton (neutrons are similar) has a mass of about 938MeV/c2, while the three quarks that make it up only have a combined mass of about 9MeV (which I believe they get from their interaction with the Higgs Field), the other 99% of the mass comes from the immense binding energy of the strong force that's holding those quarks together. With a bit of that coming from the nuclear binding energy within the nucleus (which is also the strong force in action, )
You may be familiar with the concept of mass-energy conversion, E=mc^2 and all that? That's actually a pop-sci misstatement that describes a fundamental misunderstanding of the nature of mass. You can do *matter* to energy conversion, because deep down matter fundamentally *is* energy, while mass is a fundamental property of that energy that remains unchanged regardless of the form that energy takes, more intuitively expressed in Einstein's original formulation: m=E/c^2 (see some similarity to the mass units I used above?). Convert some of that matter to energy, whether by burning coal or annihilating antimatter, and the mass of the photons the energy escapes as will exactly match the mass that no longer exists as matter. Somehow store 100% of the energy from those photons by stretching a spring, and the spring will gain the exact same mass the photons had.
And as it happens, at the current time in our universe almost all the (visible) energy has condensed into the form of the strong-force binding energy within protons and neutrons.
Currently scientists have managed to express the strong force, weak force, and electromagnetism as different manifestations of a single more fundamental force, and the dream is very much to eventually figure out how to integrate gravity into that model as well to form a single Unified Field Theory. But to date nobody has done so - and if they succeed it will almost certainly mean that gravity is NOT actually a warping of spacetime, but rather some quantum field effect that makes the math come out the same.
As its stands though, nobody has come close to unifying gravity with the other forces, and there are a lot of people that believe that gravity really is a fundamentally different force than the others. There's even people that suspect it may be the tension between those two fundamentally incompatible forces that causes things quantum wavefunction collapse at macroscopic levels - something that is completely unexplained by Quantum Mechanics, and yet is fundamental to pretty much every interpretation of Quantum Mechanics except Many Worlds (wherein the wavefunction never collapses, it just looks like it did from our limited perspective within an infinite multiverse).
(Score: 1, Informative) by Anonymous Coward on Thursday August 11 2022, @04:40AM (10 children)
Unification of the weak and electromagnetic forces was accomplished a while back. Combining that electroweak unification with the strong force is Grand Unification, and that's still sketchy, but less so than including gravity. The current crop of Grand Unified Theories have thus far not yet been experimentally verified. Though we can't build an accelerator that can reach the theorised grand unification energies, the theories have some low-energy consequences, such as proton decay, which hasn't been observed experimentally either.
(Score: 2) by Immerman on Thursday August 11 2022, @05:40PM
An excellent clarification - I didn't want to touch the details without researching them first.
(Score: 2, Informative) by khallow on Thursday August 11 2022, @10:22PM (8 children)
GUTs are actually a specific sort of combining. The Standard Model, for example, combines the three forces as well, but it doesn't predict proton decay. The key difference here is that the Standard Model treats the electroweak and strong forces as orthogonal - no interaction between the forces even at those high energies. If there was an interaction, then that would allow a means for protons to decay in the odd way predicted by GUTs.
(Score: 2) by Immerman on Friday August 12 2022, @12:32AM (7 children)
Umm, no. The standard model does NOT combine (unify, in context) the three forces, it treats as three independent forces. That's what orthogonal means. The whole point of unifying forces is to understand them in terms of a the same force acting in different scopes.
(Score: 1) by khallow on Friday August 12 2022, @02:23AM (6 children)
That is indeed a combination of the three forces.
(Score: 2) by Immerman on Friday August 12 2022, @03:05AM (5 children)
in this context combine means unify, or "treat as a single force"
Treating them as three independent forces does NOT do that.
(Score: 1) by khallow on Friday August 12 2022, @03:17AM (4 children)
Sorry, it does. It's just a special case where the single force can be factored into three independent components.
(Score: 2) by Immerman on Friday August 12 2022, @12:57PM (3 children)
If it can be "factored" into separate forces, that implies it can be unified back into a single force.
So - in the standard model, what is that single force?
(Score: 1) by khallow on Saturday August 13 2022, @12:15AM (2 children)
(Score: 2) by Immerman on Saturday August 13 2022, @07:18PM (1 child)
Sorry, no. You can't just say "tautologically they must be..." - your tautology is false.
Words have meaning. In this context:
Model = a rigorous mathematical description of exactly how everything behaves
Unified = in terms of one single force that behaves in a consistent manner
(Score: 1) by khallow on Saturday August 13 2022, @09:53PM
(Score: 2) by captain normal on Wednesday August 10 2022, @09:17PM (3 children)
Two days and six comments and no one has referenced Star Wars? What no Sci-Fi geeks?
"It is easier to fool someone than it is to convince them that they have been fooled" Mark Twain
(Score: 3, Insightful) by Immerman on Thursday August 11 2022, @05:46PM (1 child)
Why should we comment? Almost every physics-related post is about force, and the jokes will rapidly wear thin if you use them without a particularly choice prompt.
And, yes, that means more than just having the word "force" in the title.
(Score: 0) by Anonymous Coward on Thursday August 11 2022, @11:03PM
Fortunately that doesn't apply to stories about lasers and sharks . . .
(Score: 2) by DeVilla on Saturday August 13 2022, @02:28PM
Well, when skimming headline a few days back I misread it as being "The Strength of The Force".