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As a practicing physicist in quantum information, I can say

(1) "New physics" is jargon understood by experts to mean new fundamental physics, i.e., new laws/forces/particles at the base of our theoretical edifice. This does not mean that non-fundamental physics is necessarily less important -- see for instance the late Phillip Anderson's "More is different" [ https://science.sciencemag.org/content/177/4047/393 ] -- but the distinction is real and meaningful. The use of this phrase does not equate physics with HEP physics. The reason you might make that mistake is because...

(2) To my knowledge, every single discovery of new physics in the past half century years has been made with a particle accelerator. I am confident that a new particle accelerator is a lot more likely to discover new physics than building a quantum computer or any other experimental work in quantum information. This, I'm sure, is the consensus view, even among people who put a low credence on the chance that new physics will be found at the next accelerator, or that such an investment is worthwhile.

(3) In my opinion, the strongest argument for pursuing quantum information experiments over HEP is that a departure from quantum mechanics would be more revolutionary than merely finding another set of particles and forces with largely unexplained parameters. In that sense, you need to make the reverse argument to the one you are trying to make, i.e., that quantum information is more fundamental than HEP. But for the very same reason, discrepancies with quantum mechanics are just very, very unlikely to be found.

The Majorana fermion was just observed and reported this past year. Fundamental physics. Foundational physics.

No accelerators needed.

Bose-Einstein condensates have been observed and used in a variety of situations.

No accelerators needed.

And I could go on.

The point is though, fundamental foundational physics is available and accessible in all the various sub-fields.

Quasiparticles aren't changes to the theoretical foundations. They can be derived from the existing foundations.

You might as well argue that new classes of molecules synthesized by chemists are new physics.

Recent results have often depended on observations of light flashes in large bodies of water or ice. These have sometimes involved an accelerator, but present accelerators suffice.

Many people think gravitational wave observations matter.

It would not be surprising if completely new, unanticipated plasma fluid phenomena turn up, when someone looks.

People are still trying to understand superconductivity, and have not needed accelerators thus far.

Neutrino experiments are a good example! A mistake on my part. I think you're right that the CKM parameters have been bounded more tightly with non-accelerator based neutrino experiments. (Of course, that's still HEP, and it still gets plenty of funding, so it doesn't detract from my point.)

On the other hand, superconductivity is not a good example. It's a still-confusing phenomenon, but the vast majority of physicists believe to follows directly from the known laws of non-relativistic quantum mechanics.

Not sure myself, but I wonder how much of the progress breaks down into theoretical vs experimental physics, and what types of experimental physics have paid off.

Also, are there other forms of experimental physics that don't have much coverage and could shine the light in other directions?

The rate at which new experimental input to fundamental physics is generated has slowed almost to a halt. How much you can trust theory in the absence of experimental confirmation is debated.

Not true. The LHC kills theories at the same rate as ever. What has fallen off is hypotheses that survive testing.

The only sensible way to define experimental guidance is by plausibility of the theories being falsified. (Otherwise, I rule out lots of theories every day on my walk to work because I don't witness the heretofore laws of physics melting down.) Post-Higgs and post-natural-SUSY, there are no theories that have much a priori credence. And just getting to Higgs and no-natural-SUSY, compared to the previous accelerator, took multiple decades.

This slow rate is to be compared to vastly faster rate at which new experimental input was rolling in in the '30s, '40s, '50s, and '60s.

Eh I disagree. I've never understood "new physics" to mean new fundamental physics. Anderson localization was "new physics." I mean, is discovering new Hadrons "new physics?" They're "just" new combinations of quarks. In that sense it's "just" quark chemistry! I think it's especially absurd since condmat systems can be interesting toy models for high energy systems.

But you know, whatever. The fact is that we as physicists are fighting over crumbs. We should instead be political outside our circle rather than fighting internally. The fact that our budget is orders of magnitude smaller than the defense budget is insane.

Also-also, there's plenty of tabletop fundamental experiments. Superconducting cavity based axion searches for instance.

Happy to agree that terminology may vary; for the purposes of my argument, I only need that a large fraction of physicists do use the term this way, and that that sense is meaningful and important.

> Also-also, there's plenty of tabletop fundamental experiments. Superconducting cavity based axion searches for instance.

Yes, sure, such experiments could find new fundamental physics. (And it should be funded!) But the Bayesian credence the overall field places on this happening is quite low, and certainly much lower than a next generation accelerator. No table-top experiments have found new fundamental physics in many decades.

(Of course, the accelerator is arguably a much worse deal given its extraordinary price.)

Well said. Whenever I bring up that point on physics subreddits I also get tons of passive aggressive comments. It's super toxic.

The HEP people in my own department also seem to believe that anything other than beyond the standard model physics isn't fundamental or isn't pure enough to care about.

I think a lot of it comes from the fact that they used to be the golden child of science, but the influence and prestige of HEP has been a victim of it's own success. HEP just doesn't hold the same importance it used to, and that stings for the people who dedicated their lives to it.

As they pushed to higher and higher energies and events with lower and lower cross sections, they're solving problems that matter less and less, and are increasingly less likely to be useful in any way.

Of course, it's still incredibly interesting to know about the fundamental building blocks of the universe, but without a promise of practical applications, or at least a convincing argument that they'll find something interesting with this new collider, I find it really hard to justify the price tag.

Would knowing what physics does at 100TeV be any more valuable to us than a great work of literature? I'm not sure.

> they're solving problems that matter less and less, and are increasingly less likely to be useful in any way

Can you expand on why you think this? I'm not a physicist, but I feel like one shouldn't discount the possibility of useful discoveries. I'd love to hear if there are reasons that's not true.

The problem is that the effects they're looking at are confined to such high energy and small length scales that they're utterly invisible to things even on the scale of a single proton. It's very difficult to imagine how (or even why) one would ever build a device that takes advantage of a TeV scale effect to do something useful, given that these effects are meaningless to the sorts of matter we care about and interact with.

Is it possible that we might discover something revolutionary at 100TeV that will have gigantic consequences to our daily lives? Sure. But that's like saying that it's possible that there's a treasure chest full of gold buried in your backyard. Yes, if you dug up your back yard it is possible you'll find something amazing and life changing. But for right now, we don't really have any convincing reason to think that's the case, and you'd probably just be spending a lot of effort to dig a big hole in the ground.

Arguing that it'd have good effects like increasing your fitness and "who knows, you might strike gold!" isn't really a convincing argument for me to dig up my yard.

That makes sense, thanks for the reply. At those energies, I guess you'd be hard pressed to make a useful 'finding' that could be utilized outside of a huge collider.

You could say the same during invention of quantum mechanics: "They are looking at the effects on the scale of single atom/electron, hardly ever useful in our everyday life." Or about going to the space. You can never know what new discoveries bring.

Yeah, but discovery costs resources, and on the margin a new accelerator is a less cost-effective means of producing productive new discoveries, sounds like.

Except we know, and the founders of quantum mechanics also realized, that the properties of the matter we care about and interact with is driven by the properties of electrons and atoms.

That analogy has broken down. It’s not to say that we couldn’t learn something at 100TeV that could be useful or even revolutionary like QM was, but we also don’t really have any reason to believe that right now other than cheery optimism.

I’m all for finding high energy physics, I just don’t think it can justify it’s current budget in the quest for newer bigger colliders at higher and higher energies.

Non-sequitur.

Quantum mechanics didn't require $10B (or whatever the equivalent would be in 1930-ish currency) to create. The "inventors" of QM were trying to explain measurements that were already made, quite inexpensively, that did not fit the model of nature that we had at that time.

Basically, the experiments were done, measurements made. Now the theorists were trying to understand what they needed in order to be able to provide a model that fit these results. This required a number of specific mental leaps of faith. Some of these are controversial even today. But they fit the experiments, so the issue for us is one of a mental model.

But ... and this is critical, not all of physics is quantum mechanical. Orbital calculations don't (normally) require QM. Steam engines, heat engines, etc. don't normally require QM.

The objections some of us have with classifying "all of physics being HEP" is that it is not, and the reality is that most physics do not require accelerators. Most new physics won't require accelerators.

A great example from earlier this year is the first sighting of a Majorana fermion[1]. Though this article also makes the mistake of "In particle physics, fermions are a class of elementary particles". Its not in particle (HEP) physics. Its in physics.

[1] https://news.mit.edu/2020/first-majorana-fermion-metal-quant...

I agree that it is too expensive and therefore probably should not be done. But this is a totally different argument than "probably useless".

Also, look at the military budget and think what is potentially more useful...

The federal government just wrote a $2T stimulus check of funny money they pulled out of thin air to (largely) cover for their incompetence in handling the pandemic. But $10B (that's a factor of 200x less!) for basic physics research is somehow too expensive? Our priorities are way off.

I agree with your point but it skips over a different equally important thing completely: technology built to create and observe events at these energies are not without value, similarly to NASA going to the Moon and inventing Velcro while at it (yes, not true, but you get the idea).

Actually I don't think I skipped over that. I explicitly mentioned "spinoff technologies" and in my analogy to digging a hole in your back yard I said

> Arguing that it'd have good effects like increasing your fitness and "who knows, you might strike gold!" isn't really a convincing argument for me to dig up my yard.

What I mean by this is that I don't think that the spin off technologies or discoveries from high energy particle physics research (i.e. the fitness you might gain by digging up your yard) are a valid justification for doing it.

Spin off technologies and discoveries will be found in almost any research endeavour, including other particle physics experiments that aren't just "build another collider, but bigger", they're not a justification for the research, they're a bonus.

> but without a promise of practical applications, or at least a convincing argument that they'll find something interesting with this new collider, I find it really hard to justify the price tag.

I mean, you can say that about people going to the moon, right? What data are they going to get? Something about rocks and the consistency of the moon dust, right? The technologies developed in going to the moon got us so many things we didn't see from the goal.

This is the same for a lot of things around the frontiers of science! More experimental data is beneficial to all levels of science. Look at how many papers have been written in obscure and 'irrelevant' fields of higher mathematics only to -- 40 or 200 years later -- be found extremely relevant and useful?

The point is we don't know. It's not like we can't afford it. If the United States, for example, distributed the defense budget into social care and the sciences, we wouldn't be having a conversation about monetary distribution. It's not inherently mutually exclusive, and it doesn't have to be at the moment, either.

> Would knowing what physics does at 100TeV be any more valuable to us than a great work of literature? I'm not sure.

Those things aren't mutually exclusive.

> If the United States, for example, distributed the defense budget into social care and the sciences, we wouldn't be having a conversation about monetary distribution.

You tease us with such sweet words, something like Star Trek but more real.

I remember at the University of Chicago there was a researcher studying "breakfast physics" - what governs the peak angle of granular piles (like salt piles or grain or sandpiles), what happens at the singularity when a drizzle of honey goes from a hyperboloid of one sheet to a hyperboloid of two sheets. I think he also measured the effect of vacuum on fluid splatters.

These are all quotidian problems in I guess "condensed matter" physics which are 0) largely unsexy and ignored 1) still largely unsolved, 2) liable to watershed huge, life- and money- saving innovations, while exotic HEP and Low Temp Condensed, are still what most physics students study their way into.

My friend's thesis was about optimal mixing of granular matter. It's pretty hilarious physics and I was said also practically important in pharmaceutics and cosmetics industry.

100% as a fellow non-HEP (practicing) physicist -- There's so much more to physics.

Science, at least from the funding perspective, has always leaned toward what's fashionable -- "nuclear" dominated following WW2, "particle" has had it's moment, and we're moving full force toward "quantum" (& "AI"!)

Scientists seeking funding bend themselves in knots to ensure they include all the key words in their grant applications

So, what other types of physics is not well understood and requires funding to further research. We know F=ma, things in motion stay in motion, blah, and so on. We know a current flowing down a path will generate a magnetic field. We electrons moving to a lower energy path will release energy. We know light bends in a lens, and how to make that useful. Essentially, the funding for pure research and discovery is going to be more exciting than how to take a current understanding of physics into a way of making money. Plus, that kind of research should be undertaken by private investment.

One very simple way to answer this question is that the American Physical Society publishes journals called Physical Review {A,B,C,D,E}. Of these, Phys Rev D is the one focused on high-energy physics.

If there was no other interesting physics requiring further research, how could those other fields be generating enough papers to fill 4 journals?

And this isn't even counting more recent journals like Phys. Rev. Fluids.

Super conductors, semiconductors, cosmology, qm (including computing), and optics to name a few. There's still significant research to be done in all these fields, and more.

> semiconductors

even after decades of massive use ?

Oh yeah. In fact, that's exactly where there needs to be more research.

Get superconductivity working at say 0 deg C and you will be able to pick your accolade and price. Get it working at 100 deg C and you will have won the world.

I'll take 77 K any day of the week, especially if you can run a magnet with it at that temperature.

Note for the wider audience: 77 K is liquid nitrogen, vastly easier to produce and handle than liquid helium.

Quite right. The day when you can engage Heston Blumenthal to do your super conductivity experiment, is the day you have won!

(HB is an experimental chef who uses quite a lot of liquid N. Liquid He is probably not indicated for food prep)

https://en.wikipedia.org/wiki/Free-electron_laser

These things allow to create warm-dense matter in a laboratory:

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

There's always new physics in the next digit of theory or experiment. It's not sexy, and doesn't fall into (subjective) notions of "fundamental." Discovery may be hard, but can't be ruled out.

SM/beyond SM is the only field in fundamental physics though. Everything else is either a consequence of those models or applied physics.

It depends on whether you regard quantum gravity as SM/beyond SM or not.

Even if you don't, though, there's still cosmology and black hole physics.

True. I don't know much about cosmology.

…and (if I may add) foundations of quantum mechanics (which may or may not be related to quantum gravity). And dozens of open questions in relativity alone (that have little to do with black holes).

I personally find the entropy connection with information theory and black holes fascinating.

I'm a big fan of Phil Anderson's article, More is Different[1] where he argues why he things this reductionist view (the view that the physics most worthy of understanding is the physics of the smallest things) is flawed. The fact of the matter is that at all sorts of scales regularities in the laws of nature emerge, and understanding the smaller and smaller building blocks is only one interesting path for physics research.

Condensed matter physics is, in my opinion, a far more interesting and varied field of study than high energy physics. Not only does it contribute to society in a way high energy physics no longer does, but in many senses it takes on a fundamental character like HEP. Every material in the long wavelength limit acts like its own little universe with its own set of fundamental particles and quantum fields.

The universes Condensed matter physics studies have supersymmetry, Majorana fermions, magnetic monopoles, dualities and any other genuinely interesting physical phenomenon you could want.

What's more is that by understanding the physics of these phenomena, we can create new technologies that really matter.

[1] https://www.tkm.kit.edu/downloads/TKM1_2011_more_is_differen...

we haven’t really understood quantum theory yet on a theoretical level.

Everybody seems to agree with that, yet it seems most Physicists immediately refuse to spend any further thought on it and go back to modeling what happens if you double the number of particles and then crash them at 100 TeV

I'm sorry, but I disagree with the label "fundamental" here.

One can observe anti-de Sitter spaces in superfluid systems. Is that not more "fundamental" than zoology of particles and their interactions? That has, literally to do with the metric tensor of space. Seems to be a bit more fundamental to me than things interacting in that space.

Put another way, the "fundamental" argument is very weak, and everyone outside of HEP knows this.

> the pseudo-quantum stuff of adiabatically cooled circuits

Where is the innovation/research in this area happening? This is one of those topics that I find very interesting but any attempt to serious inquiry into it tends to result in ridicule from people I know with some expertise in physics and thermodynamics, as though it was just obviously nonsense.

HEP stands for High Energy Physics, which is what is done with an accelerator.

We already have quantum computers, at this point that’s not new physics it’s engineering. And if the well established frameworks don’t settle your thirst for understanding quantum mechanics, thats about philosophy not physics.

That’s as silly as saying “we already have particle colliders, at this point they’re just an engineering problem”. It completely misses the forest for the trees.

Yes, quantum computing is not a problem in modern fundamental physics. Yes, collider construction is not a problem in modern fundamental physics.

Well ... no. We have several interpretations of QM, one of which has been dominant for most of the last century. But the other interpretations have been getting deeper looks due to things that the current interpretation "hand waves" (particle wave duality, etc.)

We are generally willing to accept the interpretation, as long as we don't look to closely at it. Once we do, we have to start asking questions of nature as to which (set of) interpretation(s) are more likely correct. As in provides an understandable model, and provides correct calculation capability for predicting features given experiments.