There’s a wonderful interview with Perimeter Institute director Neil Turok here, entitled The Ultimate Simplicity of Everything, and done for a Canadian radio program.
Turok discusses his point of view on whether we’re at “the end of physics”, and I’m very much in agreement with what he has to say:
I think what people are sort of expressing is that we haven’t had a big revolution in physics. String theory was hoped for to be that revolution in the 1980s but it hasn’t really panned out in the sense that it hasn’t given a single prediction. Instead it’s given us a huge collection of theories where, if you like, there’s no overarching theory to tell which particular version of string theory is the one that describes the world. It’s almost self-destructed, I would say because it turned out to be not just one theory but this vast collection of theories which could all give different descriptions of the world.
So I think that sort of theoretical catastrophe, as I view it — meaning the logical pursuit of quantum mechanics and relativity over a hundred years was tremendously successful at some level but finding its own successor theory, it hasn’t been successful. I think that is also laying the ground for some sort of revolutionary change in the sense that we basically will have to go back to the founding principles. It looks like the founding principles of modern physics — quantum theory and relativity — have played out and they have not given us the answers we need. And so we have to go back and question those founding principles and find whatever it is, whatever new principle will replace them. So matching these great puzzles posed by the observations are equally great puzzles in our fundamental theories. And so that is just a wonderful thing to contemplate in itself. I mean, partly people become very pessimistic and say, oh my god, I’ve devoted 50 years of my life to studying this incredibly technical and difficult theory and now I find it’s blown up in my face, it’s not giving any predictions at all…and so some people talk about the multiverse where the universe would be wild and chaotic on large scales and almost anything you could imagine would actually exist somewhere in the universe. I mean, this is literally a scenario which became very popular among a category of physicists, that there is a multiverse out there. Yet the evidence is exactly the opposite. That, as we look around us, things could not be simpler. There’s no evidence for chaos on large scales in the universe. It’s totally the opposite. It’s pristine, elegance, minimalism is all we see. So, I think this is a very, very exciting time to be doing theory. The challenge is enormous. The clues are enormous. We’re waiting and we’re preparing and we’re encouraging people to take radical leaps.
“The chance is high that the truth lies in the fashionable direction. But, on the off chance that it is in another direction – a direction obvious from an unfashionable view of field theory – who will find it? Only someone who has sacrificed himself by teaching himself quantum electrodynamics from a peculiar and unfashionable point of view; one that he may have to invent for himself.” – Feynman’s Nobel prize lecture, 11 December 1965.
“It’s almost self-destructed, I would say because it turned out to be not just one theory but this vast collection of theories which could all give different descriptions of the world.”
Obviously Turok as most of String theory denialists is mixing the notions of a theory and the solutions (or vacua if you like) of a theory.
The theory is one and unique, the solutions are maybe many.
Giotis,
“Obviously Turok as most of String theory denialists is mixing the notions of a theory and the solutions (or vacua if you like) of a theory.”
So you would be comfortable putting David Gross and Gordon Kane in the ST-denialists category? Because they also say that ST is a framework, and only once you choose a particular vacuum you fix one particular theory. In that theory you can then fix various boundary conditions that specify one particular solution or another.
The way I understood ST is that the choice of the vacuum is not a boundary condition within a theory, but the choice of the theory within a framework, just like you can choose the gauge group SU(3)xSU(2)xU(1) within the QFT framework to get one particular theory (the SM).
Btw, this isn’t my analogy. David Gross was very explicit about this during the Munich conference, and I’ve also heard a bunch of ST experts make similar statements for years now. I don’t think Turok has anything mixed up here.
🙂
Marko
“There’s no evidence for chaos on large scales in the universe.” OK, but if Physics is only interested in scales where there is simplicity, the “large” ones, what’s all this other stuff? Fortunately for those who are willing to get their hands dirty there is condensed matter physics, biophysics, etc. http://www.forbes.com/sites/chadorzel/2016/03/13/why-isnt-the-biggest-conference-in-physics-more-popular/#6d10d6f77594 makes a worthwhile case at least for the CM.
Without detracting from the utility and intellectual interest of effective simple models, it’s not necessarily that the world is simple, it can equally well be that we sift the world for simplicity; it might be inadvisable to be in denial about the dross.
Giotis: “String theory denialists”. You make people who disagree with string theory sound like the flat Earth society. People who disagree with string theory aren’t denialists because it is not a proven theory. I’m afraid you’re the one who comes across with a head-in-the-sand worldview.
Peter Morgan, yes, Neil Turok says we live in the “messy middle”. So there’s plenty of complexity yet to be understood in the middle scales. In fact, that’s probably going to be more of a challenge in the long run.
The statement “Yet the evidence is exactly the opposite. That, as we look around us, things could not be simpler. There’s no evidence for chaos on large scales in the universe” doesn’t feel quite right to me.
My understanding is that the one point that hypotheses such as the multiverse bring to the table is to highlight what may be an unjustifed assumption – i.e., we cannot at this point be sure that what we measure locally is an accurate representation of what may exist on larger scales.
I hope that ssomeone will one day prove that cosmic inflation happened to all of the universe, or none. But until that time, it seems it is logical to leave open the possibility of disconnected regions…however distasteful we find the idea …
Cormac,
Frankly, I think it’s about time we made some unjustified assumptions that can be tested. In science, hedging bets can be toxic.
Why don’t we try assuming that certain things are simpler than we think they have any right to be, and then—at worst—find out exactly how and why that turns out to be wrong? If the multiverse forces itself on our attention because of unexpected observations that would be a tremendous improvement over the current situation.
Of course, for that to happen we will almost certainly need a much better formulation of the idea than we have now.
Apropos the above discussion, and Turok’s statement,
“…and so some people talk about the multiverse where the universe would be wild and chaotic on large scales and almost anything you could imagine would actually exist somewhere in the universe. […] There’s no evidence for chaos on large scales in the universe. It’s totally the opposite. It’s pristine, elegance, minimalism is all we see.”,
I believe that this part of a Feynman’s lecture is very relevant: https://youtu.be/-Km7-6-J81k?t=18m20s .
Feynman speaks about a slightly different issue, also related to anthropics, but the way I see it his argument is equivalent to Turok’s argument against the multiverse.
Cheers!
vrskin,
Thanks for the the link to the Youtube Feynman lecture videos. Wow.
We may get some new sense of how messy the middle really is by summer. Jester tells us the 750 GeV bump is…not dead yet. In fact…no, I don’t want to get my hopes up!