[d_burfoot]

When I was a physics student, there were four forces: strong, weak, EM, and gravity. That picture seemed neat and clean. Strong kept the nucleus together, EM kept molecules and atoms together (or broke them apart), gravity kept astronomical bodies together, weak was some kind of momentum-accounting device.

Recently, GPT informed me that the strong force is really a tiny after-effect of the "QCD force" (in the same way that the Van der Waals forces are after-effect of EM). Also, more and more questions about "dark matter" seem to be building up, suggesting that the standard Newton-Einstein story of gravity is far from the complete picture.

25 years ago it seemed like physics was mostly complete, and the only remaining work was exploring the corner cases and polishing out all the imperfections. It doesn't feel that way anymore! The confusing part is that modern physics is so unbelievably successful and useful for technology - if the underlying theory was way off, how could the tech work?

[HansHamster]

> Recently, GPT informed me that the strong force is really a tiny after-effect of the "QCD force"

Maybe you should not take everything GPT tells you at face value? I have no idea what this QCD force is supposed to be. The strong force is _the_ force of QCD. The Standard Model still considers the electromagnetic, weak and strong force. The description of the weak and EM force can be unified into the electroweak force and there are theories that try to also unify it with the strong force and even gravity, but there are issues on the theory side and no clear evidence on the experimental side as to which direction is the correct one.

The Standard Model and General Relativity are still our most successful theories. It is clear that they don't tell the whole picture, but (annoyingly?) it is not clear at all where this is going.

Just for dark matter there are probably a dozen proposed hypothetical particles, but so far we have found none. But maybe it's something completely different...

[elashri]

> 25 years ago it seemed like physics was mostly complete, and the only remaining work was exploring the corner cases and polishing out all the imperfections

Around 125 years ago, many thought the same about physics, that physics is mostly complete and it just explaining and finishing some edge cases and polishing all our measurements. There was just two things that were a little bit puzzling, the "looming clouds" over physics (per Kelvin description) will later lead to both Quantum Theory and Theory of relativity (Black body radiation and Michelson–Morley experiment) and the fundamental change of our understanding for physics after that.

So I would not take this position. Does this mean we are in a similar moment? maybe, who knows?

[adrian_b]

"QCD force" is the same thing as the "strong" force. There is no reason whatsoever to invent any new name.

There are several hierarchical levels at which the strong interaction and the electromagnetic interaction bind the components of matter.

The electromagnetic interaction attempts to neutralize the electric charge. To a first approximation this is achieved in atoms. The residual forces caused by imperfect neutralization bind atoms in molecules. Even between molecules there remain some even weaker residual attraction forces, which are the Van der Waals forces, which are thus at the third hierarchical level.

For the strong interaction, there are only 2 hierarchical levels, approximate charge neutralization is achieved in nucleons, which are bound by residual attractive forces into nuclei.

So the forces between the nucleons of a nucleus correspond to the inter-atomic forces from inside a molecule, not to the Van der Waals forces between molecules.

[bmgxyz]

> 25 years ago it seemed like physics was mostly complete, and the only remaining work was exploring the corner cases and polishing out all the imperfections. It doesn't feel that way anymore!

Physicists thought the same thing c. 1900, but then one of the "corner cases" turned into the ultraviolet catastrophe[1]. The consequences of the solution to that problem kept the whole field busy for a good part of the 20th century.

I'm highly skeptical of the idea that physics is anywhere near complete. The relative success of our technology gives us the illusory impression that we're almost done, but it's not obvious that physics even has a single, complete description that we can describe. We assume it does for convenience, in the same way that we assume the laws are constant everywhere in spacetime. I view this as both exciting and terrifying, but mostly exciting.

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

[qnleigh]

> Recently, GPT informed me that the strong force is really a tiny after-effect of the "QCD force"

This is kind of just semantics. QCD describes both the force binding quarks inside protons and neutrons, and the residual force binding protons and neutrons. This is all part of the Standard Model, which has been essentially unchanged for the last 50 years. The big theoretical challenge is to incorporate gravity into this picture, but this is an almost impossible thing to explore experimentally because gravity is very weak compared to the other 3 forces. That's why the Standard Model is so successful, even though it doesn't incorporated gravity.

You might enjoy https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_p...

[dxdm]

> The confusing part is that modern physics is so unbelievably successful and useful for technology - if the underlying theory was way off, how could the tech work?

Who says "way" off? It's not complete to explain everything, but it explains a lot correctly enough to use it for calculations, predictions and practical effects. Same way Newton was and remains useful, and how people have been using maths and technology to solve problems for a long time since before Newton was born.

[tacitusarc]

I think physics has felt pretty incomplete since the confirmation of qm non-locality in the 60s.