Neil Turok gave a talk last week, entitled The Astonishing Simplicity of Everything. In it, he argued that our current understanding of physics is really quite astonishingly simple, and that recent discoveries seem to be confirming this simplicity.
For the right sort of person, this can be a very uplifting message. The audience was spellbound. But a few of my friends were pretty thoroughly annoyed, so I thought I’d dedicate a post to explaining why.
Neil’s talk built up to showing this graphic, one of the masterpieces of Perimeter’s publications department:
Looked at in this way, the laws of physics look astonishingly simple. One equation, a few terms, each handily labeled with a famous name of some (occasionally a little hazy) relevance to the symbol in question.
In a sense, the world really is that simple. There are only a few kinds of laws that govern the universe, and the concepts behind them are really, deep down, very simple concepts. Neil adroitly explained some of the concepts behind quantum mechanics in his talk (here represented by the Schrodinger, Feynman, and Planck parts of the equation), and I have a certain fondness for the Maxwell-Yang-Mills part. The other parts represent different kinds of particles, and different ways they can interact.
While there are only a few different kinds of laws, though, that doesn’t mean the existing laws are simple. That nice, elegant equation hides 25 arbitrary parameters, hidden in the Maxwell-Yang-Mills, Dirac, Kobayashi-Masakawa, and Higgs parts. It also omits the cosmological constant, which fuels the expansion of the universe. And there are problems if you try to claim that the gravity part, for example, is complete.
When Neil mentions recent discoveries, he’s referring to the LHC not seeing new supersymmetric particles, to telescopes not seeing any unusual features in the cosmic microwave background. The theories that were being tested, supersymmetry and inflation, are in many ways more complicated than the Standard Model, adding new parameters without getting rid of old ones. But I think it’s a mistake to say that if these theories are ruled out, the world is astonishingly simple. These theories are attempts to explain unlikely features of the old parameters, or unlikely features of the universe we observe. Without them, we’ve still got those unlikely, awkward, complicated bits.
Of course, Neil doesn’t think the Standard Model is all there is either, and while he’s not a fan of inflation, he does have proposals he’s worked on that explain the same observations, proposals that are also beyond the current picture. More broadly, he’s not suggesting here that the universe is just what we’ve figured out so far and no more. Rather, he’s suggesting that new proposals ought to build on the astonishing simplicity of the universe, instead of adding complexity, that we need to go back to the conceptual drawing board rather than correcting the universe with more gears and wheels.
On the one hand, that’s Perimeter’s mission statement in a nutshell. Perimeter’s independent nature means that folks here can focus on deeper conceptual modifications to the laws of physics, rather than playing with the sorts of gears and wheels that people already know how to work with.
On the other hand, a lack of new evidence doesn’t do anyone any favors. It doesn’t show the way for supersymmetry, but it doesn’t point to any of the “deep conceptual” approaches either. And so for some people, Neil’s glee at the lack of new evidence feels less like admiration for the simplicity of the cosmos and more like that one guy in a group project who sits back chuckling while everyone else fails. You can perhaps understand why some people felt resentful.
4 gravitons 
Heh, you make him sound like Woit. “No evidence for BSM physics, therefore all existing theories that predicted something are falsified and those that didn’t predict anything are unscientific and my vague thoughts on new ideas being needed would surely make things magically appear in the LHC detectors”
LikeLike
Yeah…there’s sort of a continuum, really, between Woit-ish views and more practical/viable non-mainstream physics. Neil is definitely on the near end of that continuum, given that he’s actually doing something concrete/running a large organization that does something concrete.
LikeLiked by 1 person
He IS similar in spirit to W*** …
LikeLike
I’ve long wondered if there might be something Epicycle-like in QFT — some basic assumption we’ve gotten wrong. I know it doesn’t look that way; as you say, there aren’t any signposts pointing in new directions. But the GR-QFT conflict has to mean something.
LikeLike
From a string theory point of view, there totally is something Epicycle-like in QFT, where QFT’s point particles are like the assumption of circular orbits while various extended objects, like strings, fill the role of ellipses.
Now, that still doesn’t really help you with a lot of the epicycle-like stuff in the Standard Model. But that’s also a context where it’s a lot harder to get an intuitive feel for what’s wrong.
LikeLike
My first more detailed exposure to ST came from one of Brian Greene’s books, and I was much infected by his enthusiasm. As I read other sources I began to at least understand what Smolin and Woit were unhappy about. ST seems like fun mathematically, but bringing it into the physical world is problematic.
Pity, I love the simplicity and elegance of vibrating strings and how they limit how small reality can really be. (But now it’s all branes and complicated again.)
(And, damn it, I want Albert to have got it right. Matter-energy, fine, quantized, but I want smooth space-time!)
LikeLike
When it comes to simplicity, we were in paradise about 125 years ago, with Newtonian gravity and Maxwell’s equations, and the Periodic Table, but no neutrinos, no antimatter, no known radioactive isotypes, and atomic nuclei in a black box containing protons and neutrons. Everything was made out of protons, neutrons and electrons – three easy pieces and the mass of the neutron was equal to the mass of the proton plus the mass of the electron to experimental limits, suggesting that only protons and electrons were fundamental, while neutrons were composite.
We lost paradise and live in a far more complex world with fifteen fundamental masses, eight mixing parameters, four coupling constants, Planck’s constant, and a lot of integer valued parameters (three fermion families, three quark colors producing eight kinds of gluons, to parity values for charged fermion matter, antimatter pairs, one parity value for neutral fermion matter, the catalog of Higgs, W and Z bosons and photons with their respective electrical charges and spins, etc.). We live in a world where the physical laws of Nature and physical constants change with energy scale in ways only detectable at unnatural energies. The entire Lagrangian for the SM takes a whole damn t-shirt, not just five terms, and GR and the SM don’t play well with each other which is crazy because everything in the universe very obviously obeys both at all times.
Worse yet, the out of Eden world we entered needs the lion’s share of its constants and theoretical considerations to explain a bunch of phenomena that are almost never observed in Nature outside particle collider situations and then exist for microseconds or less. 90% of fundamental physics solves problems we didn’t even know that we had 125 years ago. Nobody believes deep down that the most fundamental layer we’ve pierced so far (the SM) is really as fundamental as it gets, and all of the paths back to simplicity have been rabbit holes.
Dark matter and dark energy could make it all more complicated than it was when we started.
Maybe it can get simpler if we penetrate down another layer or two, but we’re nowhere near that yet and most BSM models are more baroque than the SM before they get simpler.
LikeLike
Yep, I dont like Turok (I always feel tempted to write Tuvok ;-P …) sourballish attitude either…
It is the since centuries successful methods of building up knowledge and way of thinking that in the course of time led people to consider things that Turok seems to dislike (such as SUSY, ST, inflation, etc). Those ideas do not come out of thin air, conversely to some “more original” not so well-founded new ideas of people who try to overthrow the whole bulk theoretically and empirically established physics just for the heck and the fun of it …
LikeLike
To be fair, Turok’s favorite ideas aren’t exactly “out of nowhere” either. If I’m remembering right, his favorite alternative to inflation involves bouncing brane cosmologies, which are a minority view but not a ridiculous one by any stretch.
LikeLiked by 1 person
I really appreciated your comments, ohwilleke, which are very well expressed. I hope you don’t mind that I quoted your comment in full to my “Science vs. Universe” group on Facebook. I really appreciate your criticism not only of Turok’s oversimplified talk, but also the state of affairs in physics, the “middle era” we appear to be in where things may be quite messy indeed.
https://www.facebook.com/groups/sciencevsuniverse/permalink/940566229412455/
LikeLike