Sabine Hossenfelder

Most physicists think of beauty as the royal road to discovery; a leading critic shows it is instead the road to nowhere Whether pondering black holes or predicting discoveries at CERN, physicists believe the best theories are beautiful, natural, and elegant, and this standard separates popular theories from disposable ones. This is why, Sabine Hossenfelder argues, we have not seen a major breakthrough in the foundations of physics for more than four decades. The belief in beauty has become so dogmatic that it now conflicts with scientific objectivity: observation has been unable to confirm mindboggling theories, like supersymmetry or grand unification, invented by physicists based on aesthetic criteria. Worse, these "too good to not be true" theories are actually untestable and they have left the field in a cul-de-sac. To escape, physicists must rethink their methods. Only by embracing reality as it is can science discover the truth.

How Beauty Leads Physics Astray

Lost in Math

Gavin

A look at high-energy particle physics* in its present nightmare (of deep inconsistency and vastly expensive new data). Her thesis is that the problem is sociological and aesthetic: in the absence of new data sources, we form cliques and regroup around incompatible, unempirical beauty intuitions. 

  it leads me to conjecture that the laws of nature are beautiful because physicists constantly tell each other those laws are beautiful.

  experimentalists working with a detector developed to catch neutrinos reported on the first “interesting bounds on galactic cold dark matter and on light bosons emitted from the sun.” In plain English, “interesting bounds” means they didn’t find anything. Various other neutrino experiments at the time also obtained interesting bounds.

Her prescription is that we should stop limiting the field so heavily with naturalness or geometric naturalness or symmetry or unification or anti-fine-tuning intuitions, which collectively she (following her field) calls "beauty". Since Physical beauty is quite distinct from natural-language "beauty", I think it'd be better if we left those five components under a different name.

Filled with interviews with some of the cleverest, deepest physicists of our time (Arkani-Harked, Wilczek, Weinberg, Lisi, Polchinski) and the several bandwagons they lead, blind, in different directions. Hossenfelder herself is funny, self-critical, scrupulously clear: the kind of curmudgeonly, unbiddable empiricist we always need.

  “You ask, why do people still work on it?” Nima [Arkani-Harked] continues. “It’s in fact very funny. As I said, the best people had a pretty good idea what was going on—they were not sitting on their hands waiting for gluinos to pour out of the LHC. They also had a pretty level reaction to the data.”

But not one of those “best people” spoke up and called bullshit on the widely circulated story that the LHC had a good chance of seeing supersymmetry or dark matter particles. I’m not sure which I find worse, scientists who believe in arguments from beauty or scientists who deliberately mislead the public about prospects of costly experiments.

Nima continues: “The people who were sure it would be there are now positive it’s not there. There are people now who speak about being depressed or worried or scared. It drives me nuts. It’s ludicrously narcissistic. Who the fuck cares about you and your little life? Other than you yourself, of course.”

He isn’t speaking about me, but he might as well be, I think. Maybe I’m just here to find an excuse for leaving academia because I’m disillusioned, unable to stay motivated through all the null results. And what an amazing excuse I have come up with—blaming a scientific community for misusing the scientific method.

On the plane back to Frankfurt, bereft of Nima’s enthusiasm, I understand why he has become so influential. In contrast to me, he believes in what he does.


That sweet bitterness is telling; Hossenfelder is the broke-down hard-boiled P.I. of particle physics.

  
I shouldn’t be here, I should be at my desk, reading a paper, drafting a proposal, or at least writing a referee report. I shouldn’t psychoanalyze a community that neither needs nor wants therapy.




  I hook onto the Wi-Fi. After a week of nonstop travel, my inbox is filling with urgent messages. There are two unhappy editors complaining about overdue reports, a journalist asking for comment, a student asking for advice. A form to be signed, a meeting to be rescheduled, two phone calls to be made, a conference invitation that needs to be politely declined. A collaborator returns the draft of a grant proposal for revision.

I remember reading biographies of last century’s heroes, picturing theoretical physicists as people puffing pipes in leather armchairs while thinking big thoughts.

Her exposition is impressively clear, covering the whole standard model (and quantum mechanics, and much of modern cosmology) in plain diagrams and terse language. (Though, as usual with pop science, one can't really spot where the simplifications are misleading unless you're already an insider.)

The heavies are in general very open and undogmatic about the state of things (they can afford to be, what with tenure). Weinberg:

   I don’t know how much elementary particle physics can improve over what we have now. I just don’t know. I think it’s important to try and continue to do experiments, to continue to build large facilities… But where it will end up I don’t know. I hope it doesn’t just stop where it is now. Because I don’t find this entirely satisfying…

 I don’t take seriously any negative conclusion that the fact that the LHC hasn’t seen anything beyond the standard model shows that there isn’t anything that will solve the naturalness problem… Supersymmetry hasn’t been ruled out because it’s too vague about what it predicts.


(There's a nice bit where Weinberg hears a new philosophical/historical theory of physics - that the revolutions always involve overthrowing an old aesthetic principle - and is immediately nerd-sniped and charmed by it. Also Wilczek:

  According to McAllister, scientists don’t throw out everything during a revolution; they only throw out their conception of beauty. So whenever there is a revolution in science, they have to come up with a new idea of beauty. He lists some examples for this: the steady state universe, quantum mechanics, et cetera.
“If that was true,” I go on, “it would tell me that getting stuck on the ideas of beauty from the past is exactly the wrong thing to do.”
“Yes, right,” Frank says. “It’s normally a good guiding principle. But occasionally you have to introduce something new. In each of these examples you find, though, that the new ideas are beautiful too.”
“But people only found that new beauty after data forced them to look at it,” I point out. “And I’m worried we might not be able to get there. Because we are stuck on this old idea of beauty that we use to construct theories and to propose experiments to test them.”
“You might be right."
)

She even seeks out the ugliest theories, like Xiao-Gang Wen's string-net condensation, trying to find her own aesthetic limits:

  I am skeptical, but I tell myself to be more open-minded. Isn’t this what I was looking for, something off the well-trodden path? Is it really any weirder to believe everything is made of qubits than of strings or loops or some 248-dimensional representation of a giant Lie algebra?

How patently absurd it must appear to someone who last had contact with physics in eleventh grade that people get paid for ideas like that. But then, I think, people also get paid for throwing balls through hoops.


This bit understates a real problem (it implies we don't use Solomonoff induction out of pique rather than incomputability):

  A way to objectively quantify simplicity is by computational complexity, which is measured by the length of a computer program that executes a calculation. Computational complexity is in principle quantifiable for any theory that can be converted into computer code, which includes the type of theories we currently use in physics. We are not computers, however, and computational complexity is therefore not a measure we actually use. The human idea of simplicity is instead very much based on ease of applicability, which is closely tied to our ability to grasp an idea, hold it in mind, and push it around until a paper falls out.


Better than The Trouble with Physics which I also liked (though he was narrower and less balanced about string theory). Maybe 5/5 if I reread it. Her blog is extremely worthwhile and more technical and thus less untrue.



* OK, "high-energy particle physicists and also Grand Unified Theorists of whatever stripe including some cosmologists". But it is wrong to say that "physics" tout court has a crisis, nor indeed does Hossenfelder say this. (She didn't choose her own subtitle.)

Jeremy Cote

Note: I received an ARC of this book from NetGalley.

This was a great book, and one I hope that many people (particularly within physics) choose to read. It's not the most uplifting book, but that's the point. I'm a student within physics, and I'm happy that someone is at least shedding some light on the less appealing aspects of physics at this time. It's great to be hopeful, but if everyone is sharing the same mass delusion about supersymmetry and beauty when there is no experimental evidence for it, that's not so good.

I particularly like the fact that the author brings up the fact of a probability distribution. If one doesn't have a probability distribution, you cannot quantify how "improbable" it is for two numbers to cancel out so well (fine-tuning). It's just not possible. Yet, it seems like physicists are doing this over and over again, without recognizing they are choosing a probability distribution arbitrarily.

The author's views on beauty within physics is also nice to hear. It's fine to say that beauty has been an okay guide in the past, but there's no reason for us to think it's the only guide, or needs to be correct. This has implications, since it affects what kind of experiments are funded (to a certain extent). As such, it's important to acknowledge that we are enchanted by beauty, and this isn't a mathematical necessity.

Overall, I really enjoyed the book. I already follow the author's blog, Backreaction, and it's great as well. Read this book. It's important.

Lost in Math How Beauty Leads Physics Astray

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