New details on silicon, subatomic particles and possible ‘fifth force’

[Yaggo]

In school, 25 years ago, I was taught the "circling balls" atomic model and for me physics seemed kind of boring and very stable field of science, like we already knew almost everything.

Nowadays, thanks to superb youtube channels[1], I've learnt that we are rather in the beginning of the journey of solving the mystery of universum, and the reality is much more exciting than those boring "circling balls"; actually there are no balls at all but just "fields" (which of course is also just a mental model).

[1] E.g. https://www.youtube.com/user/TheScienceAsylum

[potatoman22]

I've always wondered why there has to be a discrete number of forces, rather than it being a spectrum describing types of interactions.

[macksd]

There may not have to be, as far as we know. From the Wikipedia page[1]:

Many theoretical physicists believe these fundamental forces to be related and to become unified into a single force at very high energies on a minuscule scale, the Planck scale, but particle accelerators cannot produce the enormous energies required to experimentally probe this. Devising a common theoretical framework that would explain the relation between the forces in a single theory is perhaps the greatest goal of today's theoretical physicists. The weak and electromagnetic forces have already been unified with the electroweak theory of Sheldon Glashow, Abdus Salam, and Steven Weinberg for which they received the 1979 Nobel Prize in physics. Some physicists seek to unite the electroweak and strong fields within what is called a Grand Unified Theory (GUT). An even bigger challenge is to find a way to quantize the gravitational field, resulting in a theory of quantum gravity (QG) which would unite gravity in a common theoretical framework with the other three forces. Some theories, notably string theory, seek both QG and GUT within one framework, unifying all four fundamental interactions along with mass generation within a theory of everything (ToE).

[1] https://en.wikipedia.org/wiki/Fundamental_interaction

[roywiggins]

The known forces, other than gravity, are mediated by specific particles that have characteristic masses and other properties.

https://en.m.wikipedia.org/wiki/Gauge_boson

(there might be a graviton, too)

With a Grand Unification Theory, they might turn out to be one force with several aspects (eg electroweak force), but that's not really a continuum.

[at_a_remove]

Forces are mediated by fields (or particles, depends on your interpretation). If you want 4.5 forces, what does that .5 look like?

Essentially, each force does describe a type of interaction. So what does one-third of a type look like?

[civilized]

I've always wondered why there has to be a discrete number of elements, rather than it being a spectrum describing different types of materials.

[mensetmanusman]

Good question. Consider the interesting fact that there are discrete energy levels instead of a continuum of energies for an electron in an orbital. This was a profound discovery at the time because it does seem like things should be more analogue than digital :)

[cjfd]

I think if there is a spectrum in interactions between the two forces joined by this spectrum would be considered one force. Of course, there is a history of forces that once appeared to be distinct turning out not to be distinct but one and the same force instead. There is a line of thinking that speculates that all four known forces are to be joined in one.

[monocasa]

> Each neutron in an atomic nucleus is made up of three elementary particles called quarks.

Well and tons and tons of virtual particles popping in and out of existance. Only a little over 1% the mass of a neutron is the three quarks normally listed.

[amerine]

Are virtual particles a real thing or just a description of the underlying system?

[tomrod]

I love that our fundamental reality is built on virtual particles. Physics rocks!

[kamaal]

>>Only a little over 1% the mass of a neutron is the three quarks normally listed.

Pardon my layman ignorance. When the particles pop in and out of existence, how does mass manage to remain the same? Or does mass keep changing and is not fixed quantity but rather a range?

And what do come out of, and where do they go?

[scotty79]

But the quarks give it it's identity. That's why they say it's made up from them, I assume.

[hongsy]

> Only a little over 1% the mass of a neutron is the three quarks normally listed.

Do you have a source for this?

[rossjudson]

It's love, right? I saw the movie.

[tiborsaas]

It's a confusing force. When two particles interact via love they possess this fore which always equate to 1LUV. Tragedy is that it's unstable and one always has more than the other, 50:50 split is rarely seen. It's even possible that during an interaction one can have all the love and the other none and they still bind together in a way.

[pharke]

>“Generally, if there’s a force carrier, the length scale over which it acts is inversely proportional to its mass,”

How does this apply to gravity, if at all?

[svenpeter]

It’s been a while since my last physics lectures so this might be wrong, but the way i understand it:

We don’t have a good model of quantum gravity yet but our best guess is that the force carrier of gravity might be a particle called graviton. This hypothetical particle has no mass and therefore the length scale of gravity would be infinite. This matches the Newtonian and the general relativity model of gravity.

This is different from the source of gravity which would be the (gravitational) mass of an object (or more accurately the components of the stress energy tensor which describe the density and flux of energy but that’s also the point where I have to start with the hand waving because my knowledge becomes very fuzzy there)

It’s also true for the electromagnetic interaction: the force carrier here is the photon which is also massless and the length scale is also infinite here.

[betterunix2]

That is the big question in physics today! There is the hypothetical "graviton" which, as you should expect, has zero mass. There are theoretical problems due to the poorly understood interaction of general relativity and quantum mechanics -- if you could resolve those problems you would have a "theory of everything."

[kazinator]

Pardon my following likely idiotic statement from a layperson, but the surprising matter of the charge distribution within the neutron suggests that the nuclear "weak force" is actually just electrostatic force. So that is to say, if the neutron is slightly negative near the surface, what if that's the entire basis of the force that makes neutrons able to bind protons in the atom nucleus. We would expect this to be a kind of dipole whose field drops off rapidly with distance.

[thayne]

First of all, the nucleus is held together by the strong nuclear force, not the weak nuclear force (the weak force causes certain kinds of decay, such as a neutron to decay into a proton and electron).

Secondly, as soon as you have multiple protons, the repulsion from the positive charges will be much, much greater than any dipole attraction.

Finally, physicists have done a lot of really precise measurements with subatomic particles, and I don't think a dipole interaction like that would match the observed results.

[betterunix2]

Actually the relationship between the weak nuclear force and the electromagnetic force is well understood. It would have to be related, given that the weak interaction is the cause of beta decay, which results in a neutron becoming a proton (which has a positive electromagnetic charge) and the creation of an electron (which has a negative charge). The force carrying particles of the weak force can also have electromagnetic charge, further demonstrating the connection between the two phenomena.

You can reason about all the forces being related in some way. For example, beta decay happens in free neutrons, but does not happen in a helium-4 nucleus; there should be a connection with the strong nuclear force that explains this. In some sense the fact that we can observe or measure an interaction implies that it must be related to other forces, since our ability to make an observation is itself dependent on such connections (in the end you need some electromagnetic effect that your eyes can perceive).

[LegitShady]

https://en.wikipedia.org/wiki/Electroweak_interaction

[dexwiz]

If this came from almost any other group it would be an easy write off. But NIST really does have some of the best analytical chemists and physicists around.

[fennecfoxen]

Headline is misleading. The "new details" are of the sort "if there is a fifth force, you won't find it over here."

> The scientists’ results improve constraints on the strength of a potential fifth force by tenfold over a length scale between 0.02 nanometers (nm, billionths of a meter) and 10 nm, giving fifth-force hunters a narrowed range over which to look.

This is not surprising and it would be possible believe this sort of a thing from a variety of qualified groups.

[retbull]

From what I read in this article they didn't prove that the force exists at all they actually showed that it wasn't present in several areas. This helps other people who are doing experiments in the area by cutting down on the range of sizes they need to look in for it but it doesn't provide evidence for its existence.

[analog31]

Indeed, and in addition, their research programs focus on improving the science and technology behind making measurements. So they have the best metrologists around too.

[wolverine876]

That's impossible. I've learned that only super-wealthy capitalists can accomplish anything.

[edumucelli]

It makes me wonder that infinite things are still "hidden" from our understanding. As the silicon is widely used on our modern society we have spent enough time studying its properties. What about other materials, there is potentially an "universe" on everything and that is incredible.

[Cats_In_Love]

I understand the interest in a fifth force is to explain the dark matter/dark energy anomaly discovered by the astronomer Vera Rubin. The orbital velocities of stars at increasing radii (radiuses?) from the center can't be accounted for by the current understanding of gravity and visible matter.

[kordlessagain]

See http://ayuba.fr/mach_effect/estes_park/ssi_estes_park_procee...

[loloquwowndueo]

Fifth force? So … water, fire, earth, air and what else??? :)

[niccl]

Quintessence. That's what it means:

  '(In Ancient and Medieval philosophy) ether, the fifth and highest essence or element after earth air, water and fire, which was thought to be the constituent matter of the heavenly bodies and latent in all things. [C15 via French from Medieval Latin 'quinta essentia' the fifth essence]

From Collins English Dictionary

[aemreunal]

...and love.

[KyleBrandt]

Pardon the comment noise, but I can't help but highlight that "Fifth Force of Nature" is an excellent name for a band.

[scotty79]

stupidity

I always treated stupidity as a fifth element that can bring great and surprising tragedies to humanity.

[LeegleechN]

The headline is misleading. The work tightened the range of possible strengths of a fifth force by a factor of 10. In other words it ruled out the existence of a fifth force within a wide range of parameters that were previously open.

[kibwen]

Note that the original article's headline is "Groundbreaking Technique Yields Important New Details on Silicon, Subatomic Particles and Possible ‘Fifth Force’" (which is too long for HN), which makes it clear that the focus is on the technique. It's the abbreviated HN title that sort of makes it sound as though the focus is on the force.

[RedShift1]

Is this fifth force something that could disappear with more precise measurements of the known 4 forces?

[vikingerik]

Good point. The details are "constraints on a fifth force if one exists", NOT behavior that indicates it does or might.

[sroussey]

Actual title:

Groundbreaking Technique Yields Important New Details on Silicon, Subatomic Particles and Possible ‘Fifth Force’

[sroussey]

“A vastly improved understanding of the crystal structure of silicon, the ‘universal’ substrate or foundation material on which everything is built, will be crucial in understanding the nature of components operating near the point at which the accuracy of measurements is limited by quantum effects,” said NIST senior project scientist Michael Huber.

[Raineer]

As a Boulderite and a huge fan of NIST, I am bummed out that the misleading headline does come from NIST itself and not an overzealous contributor.

Exciting results, all the same.

[blondin]

wait, how is what they wrote misleading?