The early version of this Edward Witten interview by Natalie Wolchover – since corrected – was criticised for suggesting his M-Theory was the only current model (with any worthwhile credibility) attempting to unify quantum and gravity fields. His idea of (M-em)branes combining multiple string theories in multiple dimensions beyond 3 is now 22 years old.
What is interesting from the interview is that he talks about it like an umbrella for a series of dialogues across multiple dualities, but which he “can’t imagine” actually resolving into a meaningful model of reality. Simply a means to the process of investigating the relationships between different quantum interpretations through mathematical dialogue – a two-way dialogue that stretches – and therefore contributes to – mathematics itself. Not just unimaginable, but:
that the world is based so much
on a mathematical structure
that’s so difficult
Whether it eventually models reality or not, it’s clear it will not be a model which inhabitants of the real world will find meaningful. Quite opposite to any suggestions of elegance or beautiful simplicity that might emerge when mysteries are resolved – not that that kind of intelligibility is itself any more fundamental than any other mystery.
Also interesting and related – I’d forgotten it originated with Wheeler – is the discussion of “it from (qu)bit” idea – the more general idea that information is the more fundamental layer of physical reality. The discussion gets tantalisingly close to the observer conundrum, that reality really does depend on the observer – the interpreter of meaning in the information – in the act of observation. Unfortunately, the (condensed) interview ends too soon.
These points are related if like me you do believe in fundamental information. Also strange in the thread of tweets that lead to the correction that there are more candidates than M-Theory, that I didn’t see mention of Quantum Loop Gravity.
There are various other candidates for a theory of everything, eg Alain Connes’ noncommutative geometry, Asymptotically Safe Gravity, causal fermion systems, E8 theory. The statement that M-theory is the only candidate isn’t only misleading, it’s plainly wrong.
— Sabine Hossenfelder (@skdh) November 28, 2017
My reading of Carlo Rovelli on QLG is that it is fundamentally information-based and appears to depend of mathematics much closer to home – analogous to Navier-Stokes equations of compressible fluid dynamics. Witten does conclude by saying:
“[Wheeler] was talking about explaining how physics arises from information.
[he] wanted to explain the meaning of existence.
I tend to assume that space-time and everything in it are in some sense emergent.
… you’ll certainly find that that’s what Wheeler expected in his essay.”
Me too. Everything is emergent from information. If Witten sees M-Theory evolving towards an information-based explanation, then I’m interested again but still hoping to see QLG taken seriously.