chickenfeet

Via hano , the most interesting article on developments in theoretical physics that I have seen in ages.  Finally a new idea that is simple, elegant and deep.

This gem appears as a comment to an article at www.theglobeandmail.com (Canada's National Newspaper!) in response to a not very good article about the search for the Higgs boson:

Jennifer Trueman from Gold River, Canada writes:
The possibility of creating a type of matter that swallows up the world as we know it is nothing to make light of. I have visited the area around the particle accelerator in Switzerland and France, and most of the people there are terrified of the possibility. Real estate values have plummeted, as people there know that should something go wrong and a black hole is created, they will be the first to go.

This has the potential to do massive damage to the global economy, and should it come to pass, there truly is no doubt -- every factory, every set of Parliament buildings, indeed, every mall and school will need to be rebuilt!

This is far bigger than the nebulous unproven concept of global warming. We need to stop it now.

The sheer bloody stupidity and ignorance of this comment is quite staggering. In the impossible event that the LHC produced a black hole big enough to suck in anything outside the collision chamber, property values would be the least of anyone's concerns, at least in the minute fraction of a second they had to have concerns.

I finally made it to the end of Roger Penrose's The Road to Reality, all 1099 pages of it. It's taken me six months, reading a section or a few paragraphs at atime because that's all my tiny brain could cope with without exploding. After about the the first seven chapters, which were more or less within my existing mathematical memory, I took a pragmatic approach to the intricacies of the mathematical argument. There was no way I was going to do the equivalent of my final year at Durham, but different courses, over again and then add a couple of years of postgrad to make it through the book! That proved a workable solution, if at times frustrating.

So what did I learn? That's not an easy question to answer. Penrose is an interesting cat. He's maybe one of three people alive(1) who have both the breadth and depth to write such a book and certainly the only one of the three likely to do so. He's also a contrarian and the dangers of approaching any subject via a contrarian are obvious though in my view preferable to taking guidance from an uncritical cheerleader type.

I'm fundamentally sympathetic to Penrose's view that one can't divorce physics from reality in a deep sense and that simply dismissing ontological problems (a la Hawking) is unsatisfactory. I also continue to be influenced by his brand of neo-Platonism which has the singular merit of being explicit while others, while claiming to be pure positivists, make claims that have no basis beyond the philosophical. This leads to a fundamental sympathy with his approach to the 'measurement problem' in QM. Resolutions of the apparent paradox that appeal (explicitly or implicitly) to consciousness just won't do. There has to be another answer and the idea that that answer is somehow related to quantum gravity is appealing on a number of levels.

I also tend to agree with his critique of string theory. I get there less from the technical arguments than from the viewpoint that anything that has been, to quote Brian Greene in a characteristic overstatement, 'the only game in town' for a quarter of a century without producing a single significant, verified, prediction has questions to answer! It's worth noting that the pundits have got vastly more pessimistic about string theory's potential. In 1988 Stephen Hawking was 'reasonably confident' that a workable scheme for integrating Quantum Field Theory and General Relativity would be discovered by the end of the century, by 1998 he was offering odds of 50/50 'within twenty years' and now the very perceptive Witten is claiming rather honestly that there really is no such thing as string theory; "We still don't know where all these ideas are coming from or heading to" (2).

Personally, I am most intrigued by the fact that Witten (doyen of string theorists) has, temporarily at least, abandoned the rather esoteric 1+9 and 1+10 dimensional spacetimes that string theorists have been so attached to and appears to be working on trying to integrate string theoretic and twistor theoretic ideas in a conventional 1+3 spacetime.

Anyway, I'd recommend the book to anyone who has a real interest in where fundamental physics is going and why. IIf nothing else it's a refreshing antidote to the 'string theory will solve everything as long as the government buys me a bigger collider' (refrain to be repeated every ten years ad infinitum.)

(1) Is there anybody besides Roger Penrose, Stephen Hawking and Ed Witten who has the breadth to really grasp the issues that trouble both the gravitation/cosmology types and the QFT/particle physics types?

(2)Witten, Unravelling String Theory, Nature, December 2005

I'm not kidding! I'm rusty of course but I've studied most of the mathematical prerequisites for QM. As well as the core stuff like vector spaces, Lagrangians and Fourier transforms, I took whole courses in functional analysis and probability theory. And still I find this stuff is so weird that my brain explodes every couple of paragraphs. It's less the mathematical formalism, it's the underlying weirdness (In contrast with General Relativity where the ideas make sense but I don't have enough algebraic topology or differential geometry to fully follow the formal argument). I completely understand why people who work with this stuff every day just fall back on the formalism and refuse to get involved with 'meaning'. Trouble is, I'm an inveterate ontologist. I had the same sort of problems with the 'classical' (Fisherian) approach to probability though that's a lot easier to resolve.

I'm now about a third of the way through Roger Penrose's The Road to Reality and I'm not finding it easy going. Despite suffering from a severe case of statistician's disease I was once a competent enough mathematician and I reckon a 2(i) in the subject from Durham probably puts me in the extreme tail of any distribution of mathematical ability/knowledge compared to the general population. Yet the blurb on the book claims it was a best seller and it still has a respectable sales rank of 567 on amazon.co.uk (contrasting with a sales rank of 370,000+ on amazon.com). So who is buying this book, how far are they getting through it and why? I'm quite curious.

I suspect this post won't be nearly as coherent as I would like but it's an attempt to get some of my thoughts about current developments in physics down in writing. It may also come off as more cynical than I intend.

The last hundred or so years has brought incredible advances in our understanding of how the universe works on both a very large and a very small scale. It's truly one of the great intellectual achievements of the human race. What I'm wondering is whether it isn't running out of steam and whether that "running out of steam" is in part an institutional phenomenon.

It's a generally accepted notion that scientific "paradigms" develop a life of their own which keeps them alive long after they have ceased to be useful and cause perfectly well intentioned and capable people to spend a great deal of time and effort developing ever more elaborate models to explain away anomalies. The ingeniousness of some of the models used to reconcile observation with the notion that the sun and planets circled the Earth is a well known example.

So is particle physics at that point now? General relativity and quantum mechanics are both relativity simple (if non intuitive) ideas but a "Standard Model" full of kluges of many orders of magnitude and an ever increasing array of particles isn't. It starts to look like a mess. Maybe the introduction of strings and branes can overcome that but when the theories seem to rely on incredibly arbitrary choices of all sorts of parameters one wonders. When reputable scientists like Hawking put forward solutions to scale problems that involve "bolting" together contradictory theories at (conveniently) the point where it becomes impossible to do experimental work because of the energy levels involved it becomes even fishier.

I also wonder how much of this is driven by the "academic industrial complex". The early breakthroughs in modern physics were often made by grad students or even people (like Einstein) who couldn't get academic posts. Now we have multi billion dollar accelerator complexes staffed by vast scientific bureaucracies. Why should a scientific bureaucracy be any less inclined to promote it's own survival and growth as a primary end than any other bureaucracy?

Look at what's happening with building large scale experimental facilities. The really tough theoretical issues turn on what's happening at the Planck scale (10^19 GeV) but the latest and greatest collider (the Large Scale Hadron Collider at CERN) is only 7 times more powerful than current facilities and gets all the way to 10^3 GeV. I'm sure it's going to allow for some neat experiments but it's pretty clear that a linear progression of bigger and better colliders isn't going to bridge a 16 order of magnitude energy gap.

I'm not nearly clever enough to see how one gets off an apparent tramline like this one but I reckon I'm pretty much as good at spotting a bureaucratic structure that's outlived its usefulness as the next guy.

It's been a really long time since I did any serious mathematics though I occasionally play around with stuff to discover whether I've forgotten everything I once knew or not. I used to be pretty decent at it. I have a 2(i) from Durham in the subject but it was a long tome ago. Also I specialised fairly heavily in probability theory and certain areas of pure mathematics so, even back then, I had the barest minimum of mathematical physics and then there's all the stuff that has become mainstream since I was a lad. So I'm challenging myself to refresh and update by working through my newly acquired copy of Penrose's The Road to Reality. It's neat. It starts with Euclid and works through to twistor theory. I am very interested to see at what point I turn into a gibbering wreck but for now it's fun to realise that I can still prove Pythagoras' theorem or derive Playfair's axiom from Euclid's parallel postulate.

Despite reading mathematics at university many moons ago, I never formally studied quantum mechanics or relativity. This was because I was much stronger in the general areas of probability theory and statistics than in physical methods so I chose my options accordingly. I still try and catch up with what's going on in the world of theoretical physics from time to time but though I think I have a decent heuristic grasp of quantum mechanics and special relativity (i.e. I think I 'get' what the mathematics mean though I couldn't actually work the math) until yesterday I really struggled with general relativity. So yesterday I was poking around some nifty stuff on the Caltech website and I suddenly realised where I had been going wrong. The fourth dimension of the standard space-time geometry isn't t as my brain had been insisting all these years (which is ironic as I know Maxwell's equations perfectly well) but ct. Suddenly space-time as a geometry makes sense and the effect of the distribution of mass-energy also falls into place. And it has only taken me just short of thirty years to figure this out!