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Musings on the Current Status of High Energy Physics (arxiv.org)
46 points by ArtWomb 14 days ago | hide | past | web | favorite | 31 comments

I have a PhD in physics, and left academia for industry (20 years ago).

One of the reasons was that physics today (or at least at that time) was dealing with exotic stuff, away from everyday life. It was not the time of Planck or Curie where within 30 years physics was boiling hot, with key discoveries almost everyday. Just look at the picture from the Solvay confrence where you see names of people you read about in a high school book.

I would hope we are in a stage like in the late XIX century, where everything seemed to be known in physics, with some tiny things still needing an explanation : the Michelson Morley experiment, the uv catastrophe etc.

The reason physics research of today deals with exotic stuff is that pretty much all of physical phenomena observable with the human eye or simple instruments has been explained. There is a lot not explained, crucial problems that indicate that the very basis of physics have to be revised in multiple ways, but that is all in the exotic domain.

That said, there is progress happening in physics, not just in certain fields. Quantum information is probably where most the the novel and insightful fundamental work is being done, and spillovers from it are affecting other parts of physics, including cosmology and condensed matter physics. As for experimental progress, there was recently a "quantum gravity in the lab" conference held at Google X [1], because we are very near the point where we can do experiments that involve both quantum and gravitational phenomena. This line of attack is hopefully going to falsify at least some perspectives on new physics and hopefully lead to some new physics. We will see.

[1] https://sites.google.com/view/quantumgravityinthelab/home

Most of the field where progress is made don't even try to look for "new physics". The foundation for quantum information theory is just classical quantum mechanics.

I got out with just an MSc, for pretty much the same reason. You know physics has lost a lot of steam[1] when the perhaps leading theoretical physicist of our time, Leonard Susskind, regularly gives talks about... how he knew Richard Feynman.

Regarding your hope: I very much doubt we’ll get to experience the following stage in our lifetime.

1. It’s amazing to think just how much steam: just as an example, you could argue that physicists determined the outcome of WWII, and with it the whole path of civilization.

> you could argue that physicists determined the outcome of WWII

If you're referring to the A-bomb, no. Germany was defeated without it, and the Japanese military didn't really care if civilians were turned to ashes.

You could argue that a combination of events ended the Pacific War, including starvation, no fuel, Russians advancing in the north, the destruction of the Japanese navy by the USA, the destruction of the Japanese army in Manchuria/Russian border, plus the A-bomb.

The Japanese Emperor was a world-class marine biologist and understood the A-bomb in general terms, but had very little influence over the military. He did a radio broadcast and survived retaliation from the military, so he does get credit for that.

Hitler and the Japanese military were die-hard end-of-the-world types. Important to realize when dealing with other tyrants. For them, there is no Plan B or surrender.

> > you could argue that physicists determined the outcome of WWII If you're referring to the A-bomb, no. Germany was defeated without it, and the Japanese military didn't really care if civilians were turned to ashes.

Germany was defeated, but the USSR was on a roll.

Without the A-bomb, there’s a decent chance the Soviet Union would’ve pushed the Anglo-Americans out of the continental Europe.

That would have been WWIII.

and took over Japan.

QTT seems like a path forward from “the breach” of current understanding.

>I would hope we are in a stage like in the late XIX century, where everything seemed to be known in physics, with some tiny things still needing an explanation

I don't see how that's possible given current uncertainties. We still haven't figured out how to relate quantum mechanics and relativity, haven't fully uncovered the deep structure of matter, and are still debating over strings vs membranes and whatnot. It seems more likely we're still missing something something foundational.

I'm almost certain parent meant the opposite: it looks as if everything is almost in place, but the UV catastrophe/Michelson-Morley eventually showed that physics had giant holes in and led to massive theoretical breakthroughs.

Amusingly, Michelson said in the 1890s "The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote...our future discoveries must be looked for in the sixth place of decimals."

Yeah that Michelson quote is what I had in mind too. It feels like that kind of situation is still possible even today.

Yes, we definitely want to arrive to a universally accepted unification of gravity with quantum field theory. The M-theory, as sophisticated and promising as it is, does not cut it for some reason. That should tell us something.

Yes thanks, this is what I meant, sorry for the lack of clarity

> We still haven't figured out how to relate quantum mechanics and relativity

Huh? Paul Dirac did it quite some time ago.

> haven't fully uncovered the deep structure of matter

VERY deep, highly irrelevant to our lives.

Huh? Paul Dirac did it quite some time ago.

I guess he meant general, not special, relativity.

>Huh? Paul Dirac did it quite some time ago.

General, not special.

>VERY deep, highly irrelevant to our lives.

1. What a foolish comment. The ability to understand, and one day control, the strong force of matter, is extremely relevant to our lives. Indestructible building materials, space elevators, economic boom from harvesting the asteroid belt, etc. Use your imagination.

2. For the purposes of this comment thread, it's irrelevant whether it's relevant to our lives our not. The assertion was physics is still far from figuring everything out. Nothing to do with our everyday lives.

We understand the strong force well enough to dismiss such possibilities. It has a range of about 1 femtometer. You're not going to be building anything using that except nuclei, and that's not going to give anything like that.

I wonder sometimes if this suspension of critical thinking about what physics will be able to give us is due to science fiction. SF from the beginning has been promising far more than science could ever deliver. We're now at the point in history all those fantasies have to be put down.

It took roughly a century from the discovery of quantum mechanics to when we started using aspects of it in real-world technology, even during a relatively primitive period of human history where we were also still figuring out mere electricity.

But I bet during the time quantum theory was first being developed it was hard to see how or whether it might be used in actual technology. I'm sure some even dismissed such possibilities. But here we are now using it to inform radio telecommunications tech, and experimenting with quantum entanglement communications and quantum computers.

A hundred of years of having the correct theoretical foundations + hacking and tinkering on them may make possible things that seem exotic or impossible now.

What? Quantum mechanics was used almost immediately to understand chemical bonds and to understand the nature of semiconductors. The frickin LASER is a quantum mechanical device! I could go on and on. The notion that QM wasn't used for roughly a century is totally false.

The laser was invented in 1960, 55yrs after Einstein published his Nobel-winning paper on the photoelectric effect. So great, in some cases it takes even less time to get from correct fundamental theory to useful technology.

The is point is - finding the correct theory sets off a process of hacking and tinkering that results in useful new technologies at some future time, some of which may not have been foreseeable at the time the theory was discovered. But we have to invest in finding the correct theory, anticipating eventually useful things will come of it, some we can foresee and some we can't.

It's possible we've gotten everything practically useful out of fundamental physics that we're going to get. At this point, phenomena not explained by the standard model occur at such extreme conditions that it's difficult to see how they could ever be technologically relevant.

> the giant resonance mode. In this mode each novel idea, once it appears, spreads in an explosive manner in the theoretical community, sucking into itself a majority of active theorists, especially young theorists. Naturally, alternative lines of thought by and large dry out. Then, before this given idea bears fruit in the understanding of natural phenomena (due to the lack of experimental data and the fact that on the theory side crucial difficult problems are left behind, unsolved), a new novel idea arrives, the old one is abandoned, and a new majority jumps onto the new train.

Reminds me of Jamie Zawinski's "CADT Model" of software development. There seems to be a dynamic in many fields where fixing known problems or finishing a project doesn't seem important to many people.

sounds like a decent simulated annealing or genetic algorithm search. which seems fine. smart people trying different ideas for a while.

I'm in favor of trying many different ideas, for a while, i.e., when a problem is new. But at a certain point you need to address issues that are viewed as critical. In the academic fields that I'm familiar with, I don't see that occur as frequently as people try new ideas that don't obviously address the most critical issues. These new ideas typically do address some issues but they might be regressions in some areas, ignore other important issues, or address the issues they focus on poorly.

In software development you have bug trackers. In scientific research you have review articles. These are useful tools that should be used to guide new work. Otherwise you're not doing simulated annealing or whatnot, you're just doing an inefficient random search.

I love reading about high energy physics and this isn't the first account from a high energy theorist which excludes weariness at the lack of progress over the last decades. We can hope that someone has a breakthrough that unlocks a new era of high energy physics. Maybe the neutrino masses hold the key or new symmetries will be found. Maybe a small alteration will make an old idea viable. So many promising ideas have been shot down: Grand Unified Theories looked for proton decays, axions looked for light spontaneously going through solid walls and supersymmetry searched for new particles. Nothing was found.

As an ex-physicist with a more experimental background in condensed matters, the real discussions and theories are way beyond me though. Just look at this paragraph from the article:

"Assume we consider two-dimensional Schwinger model with one massless Dirac fermion of charge 2 [18]. More exactly, in addition to the dynamicalcharge-2 fermion, there is a heavy probe charge-1 fermion whose mass can be viewed as tending to infinity. Next, assume that in this model we compactify the spatial dimension on a circle of circumference L, i.e. impose either periodic or antiperiodic boundary conditions on the fermion fields. Then one can show that this model has two discrete Z2 symmetries – one 0-form and another 1-form. These two global Z2 symmetries have generators which do not commute with each other [18]. Thus, only one of these symmetries can be implemented,the other one must be spontaneously broken. Hence, the ground state is doubly degenerate. In other words, we observe in this example (see Appendix on page 15 and also [17]) the power of the mixed anomalies – the prediction of the projective action of the symmetries and the ground state degeneracy. This is a strong result at strong coupling. Sorry for the pun... After [12, 13, 14] a large number of non-trivial applications has been worked out.Many relevant references can be found in [18, 19]."

My hope is that there will be a revolution in accelerator technology. The LHC is a triumph of collaborative engineering but maybe the next accelerator will be based upon different principles such as wakefield acceleration or miniaturized accelerators. Or we could find different ways of testing high energy physics, more subtle than smashing two particles together!

What, you don't even know how to 'compactify the spatial dimension'?

You jest, but I've seen the compactification (using periodic boundary condition) mentioned - and explained - in a popular science book about quantum mechanics.

Which book? I did a Master's in Physics but a while ago so it'd be nice to read something somewhat technical (but not too much).

An intro to QM by A.Zagoskin. It is indeed somewhat more technical than most pop-science books.

Does it make sense to build the FCC, when it costs so much money and doesn't necessarily have enough energy to discover any new physics, at 10x the energy of the LHC?

Maybe it makes more sense to start working towards producing microscopic black holes in space, where results about quantum gravity can be gained [1].

[0] https://www.technologyreview.com/f/612766/cern-wants-to-buil...

[1] https://arxiv.org/abs/0908.1803 , Are Black Hole Starships Possible

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