Blogs / Cosmic Variance

When the fall quarter started, there were six papers that I absolutely had to finish by the end of the term. Three have been completed, two are very close, and the last one — sadly, I think the deadline has irrevocably passed, and it’s not going to make it. So here’s the upshot.

About a year ago I gave a talk at the Philosophy of Science Association annual meeting in Austin. The topic of the session was “The Dimensions of Space,” and my talk was on “Why Three Spatial Dimensions Just Aren’t Enough” (pdf slides). I gave an overview of the idea of extra dimensions, how they arose historically and the role they currently play in string theory.

But in retrospect, I didn’t do a very good job with one of the most basic questions: how many dimensions does spacetime really have, according to string theory? The answer used to be easy: ten, with six of them curled up into a tiny manifold that we couldn’t see. But in the 1990’s we saw the “Second Superstring Revolution,” featuring ideas about D-branes, duality, and the unification of what used to be thought of as five distinct versions of string theory.

One of the most important ideas in the second revolution came from Ed Witten. Ordinarily, we like to examine field theories and string theories at weak coupling, where perturbation theory works well (QED, for example, is well-described by perturbation theory because the fine-structure constant α = 1/137 is a small number). Witten figured out that when you take the strong-coupling limit of certain ten-dimensional string theories, new degrees of freedom begin to show up (or more accurately, begin to become light, in the sense of having a low mass). Some of these degrees of freedom form a series of states with increasing masses. This is precisely what happens when you have an extra dimension: modes of ordinary fields that wrap around the extra dimension will have a tower of increasing masses, known as Kaluza-Klein modes.

In other words: the strong-coupling limit of certain ten-dimensional string theories is an eleven-dimensional theory! In fact, at low energies, it’s eleven-dimensional supergravity, which had been studied for years, but whose connection to string theory had been kind of murky. Now we know that 11-d supergravity and the five ten-dimensional string theories are just six different low-energy weakly-coupled limits of some single big theory, which we call M-theory even though we don’t know what it really is. (Even though the 11-d theory can arise as the strong-coupling limit of a 10-d string theory, it is itself weakly coupled in its own right; this is an example of strong-weak coupling duality.)

So … how many dimensions are there really? If one limit of the theory is 11-dimensional, and others are 10-dimensional, which is right?

I’ve heard respected string theorists come down on different sides of the question: it’s really ten-dimensional, it’s really eleven. (Some have plumped for twelve, but that’s obviously crazy.) But it’s more accurate just to say that there is no unique answer to this question. “The dimensionality of spacetime” is not something that has a well-defined value in string theory; it’s an approximate notion that is more or less useful in different circumstances. If you look at spacetime a certain way, it can look ten-dimensional, and another way it can look like eleven. In yet other configurations, thank goodness, it looks like four!

And it only gets worse. According to Juan Maldacena’s famous gravity-gauge theory correspondence (AdS/CFT), we can have a theory that is equally well described as a ten-dimensional theory of gravity, or a four-dimensional gauge theory without any gravity at all. It might sound like the degrees of freedom don’t match up, but ultimately infinity=infinity, so a lot of surprising things can happen.

This story is one of the reasons for both optimism and pessimism about the prospects for connecting string theory to the real world. On the one hand, string theory keeps leading us to discover amazing new things: it wasn’t as if anyone guessed ahead of time that there should be dualities between theories in different dimensions, it was forced on us by pushing the equations as far as they would go. On the other, it’s hard to tell how many more counterintuitive breakthroughs will be required before we can figure out how our four-dimensional observed universe fits into the picture (if ever). But it’s nice to know that the best answer to a seemingly-profound question is sometimes to unask it.

Hillary Clinton has moved rapidly in my mind from “You’re kidding, she won’t run for President, she doesn’t have a chance” to “Well, looks like she will run, maybe it won’t be a total fiasco” to “What a disaster — where do I donate money to her opponents?”

Hillary’s latest bit of triangulation is to co-sponsor a bill banning flag burning. It would be hard to come up with a better example of empty pandering. The United States is a rare country, one founded on ideals (liberty, self-government) rather than on an ethnic identity. The flag is a symbol of those national ideals. Laws against burning the flag have it precisely backwards: they protect the symbol by sacrificing the ideals themselves. Perhaps a subtle concept when first presented in tenth-grade social studies, but by the time you’re a United States Senator it should have sunk in.

At Daily Kos, georgia10 astutely quotes Justice William Brennan:

We can imagine no more appropriate response to burning a flag than waving one’s own, no better way to counter a flag burner’s message than by saluting the flag that burns, no surer means of preserving the dignity even of the flag that burned than by — as one witness here did — according its remains a respectful burial. We do not consecrate the flag by punishing its desecration, for in doing so we dilute the freedom that this cherished emblem represents.

Maybe Ezra is right: Obama ‘08.

I’m not sure whether it’s more accurate to describe my punditry as “fearless” or “shameless.” (This is just talking out loud, not a request for clarification.) Either way, I’ll be practicing it tonight on Milt Rosenberg’s show, a two-hour daily interview program here at Chicago’s WGN (720 on your AM dial). The other guests will be fellow Chicagoland bloggers Ezster Hargittai of Crooked Timber and Dan Drezner of the eponymous blog. We’ll be talking about — wait for it — blogging. As we are all academics, the view of the blogosphere we’ll be offering will doubtless be hopelessly narrow and unrepresentative, but fascinating nonetheless. Brief description of the show on Milt’s own blog, and you can listen live (9-11 p.m. Central) online here; it’s possible that it may be archived, I’m not sure.

I was on this show once before, several years ago, along with David Bodanis to talk about his book E=mc². My role was that of an expert in relativity. It strikes me that it took well over a decade of professional training before anyone would think such a role was appropriate. Becoming an expert in blogging was much easier.

In other celebrity news, Peter Steinberg of Quantum Diaries was nice enough to describe me as a “physics super-blogger.” I have not yet decided whether this is damning by faint praise, or at least diminuition by modest association. The proximate cause of Peter’s description was the Einstein Conference we held last Saturday at the Francis W. Parker School, which turns out to be Peter’s old high school!

This is a photo of me and Angela Olinto at the panel discussion part of the symposium, snapped by Peter’s cell phone fancy digital camera and stolen from his flikr account by me. Angela is sporting her stylish spectacles while I am gamely trying to moderate our extremely distinguished panel (Angela, Michael Levi of the SNAP collaboration, string theorist Jim Gates, Argonne theorist Murray Peshkin, neutrino experimentalist and fellow Quantum Diarist Debbie Harris, and Fermilab Director Pier Oddone).

Some of you might not be very familiar with Quantum Diaries. It’s a wonderful idea to celebrate the World Year of Physics: grab some charismatic and energetic physicists and encourage them to blog for a year about what they’re doing. Sadly the year is almost over, but fortunately that means you can leaf through all the interesting entries that have accumulated. Other personal favorites include Caolionn O’Connell, Gordon Watts, and Stephon Alexander — but they’re all good! Who knew physicists were people, too?

Update: Eszter has a wrap-up of the Milt Rosenberg show — with pictures!

Further update: audio of segments of the Milt Rosenberg show is now available.

For those in the UK with access, the television channel BBC Four will be having A Night of Numbers tonight! Here is the schedule:

*21:05 Go Forth and Multiply*
Starting a night of numbers on BBC Four, have you heard of the mathematical system that cancels out certain numbers because they’re ‘unlucky’ – and ignores fractions altogether? From time immemorial, merchants in Ethiopia have used a system of multiplication that seems bizarre – but it works.

*21:10 Music of the Primes*
Prime numbers – those figures which refuse to be divided neatly by anything other than one and themselves – are fundamental to mathematics. Yet they seem to surface entirely randomly along the number line. But are the primes truly random — or is there some hidden pattern? Marcus DuSautoy investigates the fascinating story of the great mathematicians who’ve grappled with the problem of the primes. Website here.

*22:10 Phi’s the Limit: The Golden Ratio*
What do the nautilus seashell, the Great Pyramid, and The Mona Lisa have in common? They are all feature Phi — otherwise known as The Golden Ratio.

*22:15 Breaking the Code*
The mathematical genius Alan Turing was responsible for cracking Germany’s Enigma Code – enabling the Allies to decipher messages sent by the Nazis to their forces. Derek Jacobi, Prunella Scales, Richard Johnson, Amanda Root and Harold Pinter star in this absorbing drama, revealing how one of Britain’s greatest mathematicians changed the course of the Second World War.

*23:45 The Mathematical Art of MC Escher*
Of all major artists of the 20th Century, none was more influenced by maths than the Dutch artist MC Escher. Throughout his career, this superb draughtsman produced images that explored (and exploited) mathematical ideas.

*23:50 Horizon: Fermat’s Last Theorem*
As a 10-year old schoolboy, Andrew Wiles stumbled across Fermat’s Last Theorem – one of the world’s greatest mathematical puzzles. This edition of Horizon tells the story of Wiles’ quest to solve a problem that had baffled the greatest mathematicians for more than three centuries.

-cvj

You join me in part two of my journey from home to work. Part I, together with my reasons for doing this, can be found here. We pick up the journey just after we passed another food stand serving tasty morsels. We’re still on Sunset (which by the way has a cycle lane for a long way), in the heart of Silver Lake now, and there’s a slight hill up towards the ‘hood called Echo Park, just ebfore which we’ll do our turning onto a useful side street (there are so many in this city, which is why the complaint that cycling is dangerous can be tackled a bit…you can choose to avoid a lot of the worst stuff…it does not grant you immunity, but it can help manage your vigilance a bit better). Immediately turning the corner we glimpse one of the many interesting gardens that so many people have. In fact, I could do you a whole garden tour using the route I take when I walk to the busstop if for some reason I’m not cycling. We’ll pass many more of these, along with lovely trees, etc. I won’t include any more photos, or we’ll have to do a part III and IV.

I like to pause and smugly look at the 101 freeway as I cycle over it. Annoyingly, it is not at a standstill as I took this photo, so the photo is not dramatic. Ok, I’ll come clean here: it seldom is at a standstill. What people tell you about traffic in LA is in fact over-exaggerated, most times. Try driving near London or many other major European cities and you’ll know what I mean. Traffic is not the (only) reason I choose to use public transport (and cycle). See earlier discussions. One reason is simply that if we don’t use what is there, it will never get better. And cyclists should simply not give control of the road to motorists. We have a legal right to a lane on the road when we want it, and should not be forced onto the sidewalk, or into our cars. How will drivers learn this if we don’t cycle? (See here.) I’ve said lots on this already…. If I come by here in the evening, I’m always amused to see people pulling up and getting out in all their finery for some sort of fun night out at the local night club. This one is just a doorway. I’ve not been to any of these. I passed a lot of these on Sunset too, but I did not take any pictures. There’s another neighbourhood nursery of some sort (right). Everybody seems happy.

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Well, what can I say? I’ve no idea how to begin. I decided to disappear for half the day (I’ll be working into the night as recompense, in case anyone is keeping track) and go to one of the private press screenings of Peter Jackson’s King Kong. It was held at the Arclight, that wonderful movie theatre I’ve told you about many times before. It was quite an event. I cannot show you any pictures of the gathering people, etc, because they basically forbade any electronic devices whatsoever from the theatre. I’m not kidding. They turned people away who did not listen, thinking that if it did not have a camera it did not matter. They had metal detectors and security wands. They were deadly serious. The staff I spoke to said that they’d never seen anything like that level of security for a movie preview.

What were they trying to protect? I presume it is concerns over piracy. They want this movie to be huge…..HUGE. We were filed into the theatre, and I was anticipating logistical problems. I was on my own, and there was a scramble for seats (the Arclight routinely allows you to reserve your seats for normal showings -they are yours; you paid for them (why don’t all theatres do this?)- and this is one of the reasons why it is probably the best movie theatre anywhere) because this was not a regular showing, and tickets are handed out once they have seen your invitation and checked out that you’re not a spy of some sort. Since I was on my own, how was I going to snag a good seat and then get back out for popcorn and a drink and keep my seat? (This is a three hour movie after all.) No problem. This was a classy organisation: They had tables full of complimentary popcorn and beverages for you to pick up as you went in. I’ve not had that at a preview before, but maybe this is because it was a press screening and not a test showing…. the two are different. The drinks and popcorn were those super-giant sized ones that I never buy because I can’t eat and drink that much junk on my own, but I had no choice. They were nicely decorated with stills from the movie, which was appropriate.

Unbelievably, I got nearly the perfect seat. The movie was not in the Dome, although I suspect that is where they’ll open it for general audiences. It was in one of the hardly less excellent theatres with the super-giant screens, plush seating and wonderful sound. (Actually, all the theatres in the Arclight fit that description.) There was a buzz of excitement, and they did a good job of generating good will with all the free stuff. Now I know that I’m a pawn in their hands by telling you about the movie, since I am contributing to “word of mouth” buzz that can help to…..

“Shut up and tell us about the movie!”, I hear you cry. Ok. How was it?

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Physics World has a review* of Leonard Susskind’s new book entitled “The Cosmic Landscape: String Theory and the Illusion of Intelligent Design”. The review is by Michael Duff of Imperial College (London), who is well known in the field. Well, I have not read the book, so I’ll simply point out the review, and not make comment directly on the book itself. A review of a review if you like.

I’ve always liked Mike’s sense of humour, and so it is nice to see it sneak into the article here and there, such as at the end of this key pair of paragraphs:

Susskind believes that it is more than dumb luck that the universe is so accommodating to human beings. “Can science explain the extraordinary fact that the universe appears to be uncannily, nay, spectacularly, well designed for our own existence?” he asks.

But does this mean that the religious fundamentalists have won? Must we invoke the existence of a god to account for the gaps in our knowledge? Susskind’s answer is “no” on both counts. As you might have guessed from the book’s subtitle, he argues that while “the appearance of intelligent design is undeniable”, science can nevertheless explain it all. Phew! Thank God for that.

Background (and my humble opinion) on the issue of the Landscape in string theory research can be found in an article I wrote here. (Tread carefully through the 172 (to date) comment bloodbath tagged on the end.)

So it seems, according to those two paragraphs, that Lenny is being provocative with his book title while still holding on to the view that we don’t need to go beyond science to answer several truly fundamental questions about our universe. I’m relieved, because I have great respect for Lenny, and so this is rather good news. Hmmm. We must not, however, forget that he puts forth various versions of the Anthropic Principle to answer the questions instead, and there are those (myself included) who question whether that (at least in its strongest form) is still doing science.

I have not yet made up my own mind whether it sits well with me or not….. Let me tell you one reason why I am conflicted: I don’t mind anthropic arguments when they are used to predict something important…This has been done in science before: I’ve given the example of Hoyle’s amazing result here. But I do not like an anthropic argument to be used to “explain” something we already know. These seem to be two different things in my mind. I could be wrong.

As I said in the other article, what some string theorists, led by Lenny (a very small group, despite what is often said – it is not the entire field) want to put forth is the idea that since the theory (as far as we currently understand it – key point here) seems to give us a vast number of solutions, rather than just one corresponding to our world, this should be regarded as a feature rather than a bug: This vast “Landscape” of solutions each corresponds to a different possible universe, and then we have to use the fact that we are here to ask the question “which one?” as the reason that we are here to ask the question “which one?”.

This bothers me a bit, since we already know that we are in this universe and have this solution…..and so this does not seem very predictive. It is not in the spirit of Hoyle’s precisely predicting a previously unknown resonance of the carbon nucleus on the grounds that we would not be around if it did not exist, in order to allow star to generate heavy nuclei.

Here is a long extract from the article talking about the seeds of the modern Anthropic applications to fundamental physics, in its form attributed to Weinberg:

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The laws of physics are safe for now.

It occasionally comes to pass that someone, for reasons that frankly escape me, would like to make the point that science doesn’t know everything. It doesn’t, of course, which is so obvious that the point hardly needs making. Equally obviously, science does know some things; when it comes to mundane features of the natural world, one hopes that existing puzzles will eventually be figured out.

One of the favorite anecdotes for the don’t-know-everything crowd involves the flight of the honeybee. As you may have heard, “bees shouldn’t be able to fly,” according to science as we know it. In fact, this idea goes back to French entomologists August Magnan and André Sainte-Lague, who in 1934 calculated that bee flight was aerodynamically impossible. Since bees have been observed to fly, the smart money has always been that Magnan and Sainte-Lague were, in scientific parlance, “wrong.” But that’s not the same as understanding how the darn insects actually do flit around.

Now we know. Bioengineers Michael Dickinson, Douglas Altshuler and colleages have analyzed the flight of the bumblebee (if you will), using a combination of high-speed photography and robotic models. The trick is that bees have flight muscles that have evolved differently from those of other insects — unintelligent design, I suppose. Consequently, they flap much faster than any other animal their size, and emply a unique rotation of their wings.

Chalk up another success for science. I understand that Dickinson and Altshuler will now start working on how to get experimental predictions out of string theory.

For very many years I’ve been a big fan of writer-performer Sandra Tsing Loh. I’m a radio addict, as you may have gathered from other posts, and along wiith NPR’s standard news programmes, and Stardate, her brief monologues “The Loh Down” have been things I have sought out for a long time (and before that, when she used to appear on This American Life). She’s funny, smart, intelligent, sharp, irreverent, funny… and uh, did I mention funny? I love her voice acting in her delivery, tone, timing, etc. So I was already wrappable around her finger quite a fan of her work – and then I learned (a while ago now) that she was a physicist too! Great!…which explains why she occasionally pops physics references into her work, of which I approve (for reasons I’ve spoken of here …too many times). So it seemed a disaster in 2004 when she was fired from KCRW when her technician forgot to bleep out the f-word in one of her monologues, but she got lot of publicity from the event (rightly so) and furthermore, to my delight she was picked up by my preferred local station, KPCC, where she has been ever since. (Stories here and here, for example.) (Podcasts and streams of her KPCC-based monologues here. Google for others.)

Many times while listening to her I’ve actually thought it would be great if she combined her science background with her work, becoming a powerful sort of special-ops soldier in the army to bring science to everyone…..

…Well, her alma mater, Caltech, seems to have thought it too! I just this minute heard her on KPCC in a trailer for a new show of hers (in collaboration with Caltech)…. “The Loh Down on Science”. Wow! I hope it is good….I can’t wait. For those of you who don’t get KPCC, you’ll be able to download podcasts and streams from the programme’s page, or go here.

-cvj

[Update: Oh dear. I just heard the first one. It is way too short! The theme tune, combined with the commercial for Caltech, and the other sponsors is longer than her part. I'm worried that they're going to be afraid to have actual science in there so as not to "scare" the public....Come on guys (the various scriptwriters and editors mentioned on the homepage)! This is a great opportunity...don't squander it. Give Sandra Tsing Loh something to get her teeth into. She'll make it work! Use the MacDonald Observatory's Stardate as your model, read daily by the excellent Sandy Wood. It is short but not too short and just a perfect daily taste of astronomy. Come on....try harder. Please.]

Well, I’ve been painting all day and I’m exhausted. It was not supposed to take this long! There are ten sections to the fence, and how many did I get done, after starting at 8:30am and finishing when the sun set at 4:30pm (ish)? Three. The first took as long as the second two since I only realised that I was not going to be a contender for the Turner Prize for modern art rather late in the day and so dropped my brushstrokes from “daring, yet playful; he’ll confound the critics”, to “let’s just get this stuff on the wood…please!”

So after tedious cleanup of painting things (I hate having to do that), showering (with brutal use of a scouring pad to get the day’s paint off), and preparing for this evening’s delights (editing an article), I thought I would settle down with a glass of wine and blog for a bit and tell you about my evening from last Sunday. It’s another tale from The Industry, and it starts in the Hollywood Hills….

It was in the lovely Hollywood Hills home of….. Actually, I don’t know if I should say, as I don’ t know if it is appropriate to do so. So I won’t as it does not matter. I’ll start again. It was in the lovely Hollywood Hills home of a patron of the Arts, specializing in Theatre, who has produced rather a lot of interesting work in the city. Gathered together for the evening was a very interesting collection of people. (It would have been even more interesting had the Hollywood Christmas parade traffic not nixed a couple of others… It made me 40 minutes late and I only live 20 minutes away….). First and foremost among the present were my friends Oliver Mayer, the playwright and USC School of Theatre professor, and the actress Marlene Forte. Marlene (a profile article is here) was going to do a 15 minute excerpt from a new play by Oliver. There to watch was our host, along with another actor and writer Marco Greco, another actor Gary Perez (and another whose name I can’t recall), and some other friends of the host (who I think have also produced plays and films). (The imdb links don’t contain their extensive theatre work, unfortunately) The last group was the owner of a well known Hollywood nightclub and his assistant. I’ve forgotten their names too. (This is is why I’m not in that business. I’d offend so many people at networking parties by not remembering their names……)

Oh, and I -firmly an outsider- was lurking around. In conversation, people assumed I was in the Industry too (perhaps a playwright too), and I had to tell them that was not the case. (I’m about as much of a playwright as someone who calculates their change from a $20 bill at the grocery store is a mathematician.) Rather pleasantly, I did not get the “I was never good at physics at school” speech when I said what I do, which was good.

So quite a collection of people. Why am I telling you about this? Because it was fascinating to see the creative interaction between these different parties over the matter in hand. Marlene did the extract in full character and costume, and we all sat with drinks in the living room and watched. Then there was discussion afterwards. Not because we were watching a completed work, but because there were several interests in how the piece would be completed. The potential producers were interested in it to see if they wanted to financially back it, and Oliver and Marlene -the primary creative artists in this venture- wanted to show it to these parties. Very interesting was the presence of the nightclub people. Their interest was in new work and new directions. Their venue is equipped to do the usual stuff -bands, dances, etc- but they are looking to start doing (and have already started) a wider variety of shows that will appeal to not just the kids coming for the loud stuff, but people looking for more depth in their entertainment. They are trying to be a new venue on the theatre circuit. So they came along as a potential space in which this piece to be performed. Why was the interaction interesting? Because everyone had their different takes on what they saw, which was interesting, but in addition because the play itself will be affected by this process. Everybody had such good ideas!
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