51–60 of 71 posts
I notice not-even-wrong-woit doesn't bother refuting any of the claims on their merits. Just calls it "ridiculous hype" and moves on. It's about the same level of rigor he applies to his research in LQG - Loony Quantum Gravity.
Unfortunately my understanding of physics stops at general relativity and quantum mechnics (which I did study both at uni, with some mathematical framework of understanding). How would I advance from this point, what should I read to get a grip on string theory, including the concepts and maths involved? Could you recommend some resources? Like why did they come up with the concepts they came up with, how does that h…
I think the main thing is, even if string theory turns out not to describe reality, it shows that quantum mechanics and general relativity can be reconciled within a single, mathematically consistent framework. The tension between the two is gone and it's actually needed for physical correctness. Simply knowing that such a reconciliation is possible is already a meaningful result.
String theory emerged from attempts to quantize gravity. I think the most interesting thing is that when a relativistic string is quantized, a massless spin-2 particle inevitably appears in the spectrum. This particle behaves exactly like a graviton, meaning that gravity is not introduced by hand but instead arises naturally from the theory.
Competing approaches may possibly be all compatible, much like different interpretations of Quantum Physics.
The main difficulty with experimental tests is that the relevant energy scales and distances are far beyond what we can currently probe in the laboratory. This is not a weakness unique to string theory, but a general problem for any theory of quantum gravity. The Planck scale is simply too extreme to access directly with present technology.
As for experiments that depend on both quantum mechanics and general relativity, in principle these would involve situations where quantum coherence and strong gravitational effects are both important. Examples include black hole evaporation, aspects of early-universe cosmology, and possible quantum effects in curved spacetime. These are extraordinarily difficult to study experimentally, but they are what motivates the search for a theory of quantum gravity in the first place.
It reminds of this quote from Roger Penrose's book, Fashion, Faith, and Fantasy in the New Physics of the Universe: “My nervousness was perhaps at its greatest because the illustrative area that I had elected to discuss, namely string theory and some of its various descendants, had been developed to its heights in Princeton probably more than anywhere else in the world.” “Moreover, that subject is a distinctly techni…
He's just saying he doesn't want to be eviscerated by Ed Witten, which is a pretty commonly shared sentiment in the community.
It reminds of this quote from Roger Penrose's book, Fashion, Faith, and Fantasy in the New Physics of the Universe: “My nervousness was perhaps at its greatest because the illustrative area that I had elected to discuss, namely string theory and some of its various descendants, had been developed to its heights in Princeton probably more than anywhere else in the world.” “Moreover, that subject is a distinctly techni…
Well... Penrose got himself into serious trouble speaking on issues beyond his expertise. I respect that he is now being more careful. And it's entirely possible that he isn't up to date on their tech. Why would you doubt his own words?
Unfortunately my understanding of physics stops at general relativity and quantum mechnics (which I did study both at uni, with some mathematical framework of understanding). How would I advance from this point, what should I read to get a grip on string theory, including the concepts and maths involved? Could you recommend some resources? Like why did they come up with the concepts they came up with, how does that h…
It does not presuppose a background in QFT. It does require you to know quantum mechanics. Mind you, it's not as deep as the standard texts (Polchinski et al. or Kaku's work prior to going off the rails) or my favourite which is the two-volume "Quantum Fields and Strings: A Course for Mathematicians". But it makes reading the others possible.
The first paper they link to is not about string theory. It's using math that was developed for string theory , and is perfectly valid outside it, to make predictions that can be (and are) experimentally validated. It has exactly none of the problems of string theory, and I am not sure why it's clumped with a physics paper in the blog. How is it a problem to say "hey they used string theory tools!" in a press release…
Peter Woit, the Columbia maths department computer systems administrator, makes his bread by googling the word String Theory and then posting what ever latest results come up in a disingenuous way on his blog to stir reactions from his readers.
Earlier quoted context omitted.
There is no a priori reason why a bunch of meatbags would have the ability to test all laws of physics of this universe. I think we may have gotten lucky for a while there. String theory is so far out there that a new methodology has been developed, namely using beauty or symmetry or Occam's Razor to choose between competing theories. None of these have the pedigree of empiricism, but they may also not be wrong. I ho…
Occam's razor is perfectly empirical: "entities must not be multiplied beyond necessity". It's what people repeatedly accuse string theory of violating in low-rent popsci criticism. The other things you refer to are still Occam's razor: symmetry is handy because it eliminates symmetry-breaking entities even though we know they can happen in the standard model (Higgs) and "beauty" is really just another way of saying…
I think it's better to think of most real world models as being low dimensional-ish, where there is a decaying power law of eigenvalues, and most are quite small, though not zero. You can get quite far by looking at the largest modes and ignoring small ones, but you're not exact, so you're not seeing The Truth, or whatever. Forcing your self to use fewer parameters is a way of denoising, however, that is quite effective.
It feels like Woit is just being a hater at this point. In a meritocracy, talent and funding gravitate toward the most promising options. If string theory took up a large proportion of people and resources, it’s because it solved technical problems no other framework could. Even if it hasn't yielded a Theory of Everything, the fact that its toolkit is now solving problems in other fields suggests the program has led…
In a meritocracy,
All it needs is an experiment that can test it.
If they had that the hype could die. Luckily it cannot be tested so the hype will continue in perpetuity