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Uncertain Principles

Physics, Politics, Pop Culture

Friday, October 07, 2005


I'll get around to trying to describe the frequency comb portion of this year's Physics Nobel Prize, but I had fifteen individual student meetings yesterday, at which I did the red-pen trick on their draft formal lab reports. Pedagogically, it's probably valuable for them; in practical terms, I feel like my brain has turned to mush. So you get pop music commentary instead.

Here are a few songs that are in heavy rotation in my part of Chateau Steelypips at the moment:

"Almost Saturday Night," by John Fogerty. Apparently a pretty obscure song (the version I got from iTunes is live, and he introduces it as a "cult bootleg thing"), it was a favorite of the morning DJ's on the Armed Forces Radio Network when I was in Tokyo in 1998. Go figure. It's not great poetry or anything, but it's ear-wormy, and I associate it with my apartment in Komae.

"Common People," by Pulp. Not a new song, but one of the many CD's I own that were badly ripped by iTunes, so I bought a clean copy. It's rare to find a song that has both a strong political message and a good tune and vivid lyrics. This is one of the few. The William Shatner version is a travesty.

"Soul Meets Body," by Death Cab for Cutie. I don't have much indie cred, but I make the occasional nod in that direction. Expect to see the New Pornographers further down. It's a great tune, but you knew that already.

"Jumping the Wall," by Ian Knapp. A KEXP favorite, Ian Knapp sounds a whole lot like Ben Lee, if that helps at all. This is a little more up-tempo than most of the rest of the album (Into These Oceans), but it's catchy and bouncy and fun.

"Dishrag," by Wide Right. A female-fronted (possibly all female, I don't know) band with a serious yen to be Joan Jett. Nothing terribly innovative-- it's a straightforward plea for a lover to stop cleaning up and start canoodling-- but I'm a sucker for handclaps on the chorus. They also do a "Buffalo Fight Song" which is pretty funny ("Hey, ho, let's go Buffalo/ It isn't always freezing and it doesn't always snow!"), but maybe you had to be there.

"Master of the Clouds," by the High Dials. The album title is "War of the Wakening Phantoms," so if you're expecting something a little bit trippy, you'd be right. There's a lot of weird, echoing twangy guitar (I don't know the technical term), making it sound like something off the soundtrack to a psychadelic Western. Or a less grim Tarantino movie. A Pretty good album.

"Sing Me Spanish Techno," by the New Pornographers. I told you.

"Van Gough," by Slender Means. Sort of a brag song ("I'm just biding time, until I can unveil my brilliance"), but a little more ambiguous than that. There are some great shimmery keyboard things, some Beatles-esque harmony vocals, and a great chorus. Fun retro-pop (helpfully classified as "Rock" by iTunes. Yeah, that narrows it down...). The whole album (Neon and Ruin is good).

"Bad Sake," by kingsley. More fun power-pop-- slightly woozy verses (all starting "You and I, drinking {some liquid}"), a chorus with a bit of crunch, all wrapped up in a neat little 2:16 package. "Since You've Been Gone" is also a good tune. I'm not sure if it was an EP, or if I only bought four of the songs, and I'm too lazy to go look.

Two more lab drafts to go over today, and then the weekend. Hey, it's almost Saturday night...

Posted at 7:42 AM | link | follow-ups | 4 comments

Wednesday, October 05, 2005

More is Different

It's rare to hear me say that it's easier to explain theory than experiment, but that's the odd situation created by this year's Nobel Prize in Physics. It's not that the theory is all that much simpler, but rather that Hall and Hänsch have done so many different experiments that it's sort of difficult to narrow their contributions down to a few easily explained things. Hänsch in particular is everywhere-- he presides over one of those gigantic research empires that you find in German physics, and does a little bit of everything in AMO physics.

That breadth makes Glauber's contribution seem relatively easy to explain. It's actually pretty complicated, and I don't pretend to have a very deep understanding of how it all works, but at least it's only one thing.

The key problem that Glauber's theory helps address is related to the problem of the photon theory of light. More specifically, he showed people the mathematical apparatus needed to deal with light beams consisting of finite numbers of photons.

In classical optics, it's fairly easy to understand light as an electromagnetic wave: it's a combination of an electric field and a magnetic field, oscillating at some very high frequency, and looking pretty much like a textbook sine wave. You can define an amplitude (how big the field is) and a phase (which defines where the peaks of the wave fall at any instant of time), and then you're done. This isn't a terrible approximation for a lot of simple situations, and it works very well when the photon number is very high.

It's also relatively easy to handle the case of single photons. A photon is just a bundle of light energy, and it can be scattered or absorbed just like a little particle of matter. Problems like the photoelectric effect and the Compton effect are fundamentally single-photon problems (while there may be a beam of many photons hitting whatever target you're looking at, they only interact with it one at a time).

You hit a big problem, though, when you want to start talking about smallish numbers of photons-- more than one, less than a bazillion-- because you really start to run up against the quantum nature of the field. The problem is particularly acute when you start dealing with situations where more than one photon is involved. The most famous example (for small values of "famous") of this is the Hanbury Brown and Twiss experiment (two people, not three-- "Hanbury Brown" is a double unhyphenated last name), which looked at correlations between photons arriving at a detector. They asked, in effect, what the probability was of detecting a second photon at the same detector as one they had already detected. Surprisingly (to them, anyway), they found that photons tend to "bunch"-- the probability of detecting a second photon is twice as high for very short times as it is for longer delays.

Glauber is getting his share of the Nobel Prize in part for showing that this is a natural consequence of the photon theory of light. When you consider in detail what happens to the field-- things like the fact that the number of photons changes when you detect one of them-- you get the Hanbury Brown and Twiss result very easily.

Glauber's theory makes it possible to explain a bunch of weird phenomena, and also to predict and design experiments to observe even weirder phenomena, and begin to control light at the quantum level.

He was also, very (very, very, very) indirectly, responsible for getting me this job. One of the other elements of his theory was the introduction to light of things called "coherent states." It turns out that, when you start talking about light beams consisting of finite numbers of photons, all those wonderful uncertainty relations over in the left-hand column start to come into play.

In particular, the third one down (Δ N Δ Φ ≥ 1 / 2) is an issue-- when you're dealing with a quantum light field, you can no longer use the classical definition of light as a wave with well-defined amplitude and phase. The amplitude is replaced by the number of photons in the field, and both the number and the phase need to be uncertain, with the product of their uncertainties satisfying that inequality.

The closest you can come to approximating the classical ideal is the coherent state, which Glauber introduced to quantum optics. A coherent state is a special state of the photon field in which the uncertainty product has its minimum value. The number of photons is uncertain, but fairly well known, and the phase is uncertain, but fairly well known. This is the best description of a normal laser field, with a moderate number of photons.

Of course, you can play some games with this field once you have it, and trade off uncertainty in one component (number, say) for uncertainty in the other (phase), while keeping the product of uncertainties the same. So you can make a state in which the number of photons is known very well indeed, at the cost of losing information about the phase. These states are called "squeezed states," and they have a number of applications in precision measurements (as you might expect, reducing the uncertainty in one component allows you to make more precision measurements than you would be able to otherwise).

How does this connect Glauber to my job? Glauber introduced the coherent state to quantum optics, and the idea of the coherent state leads to squeezed states of light. (which have been made by many people, in many different ways). My work as a post-doc involved using a Bose-Einstein Condensate to make squeezed states of atoms, that are exactly analogous to the squeezed states in light (that is, we knew the number of atoms very precisely, at the cost of losing information about their phase). That experiment, and the job talk that went with it, is what got me my current job.

And that, kids, is how we play "Six Degrees of Nobel Separation"...

Posted at 7:46 AM | link | follow-ups | 6 comments

Tuesday, October 04, 2005

Rah, Rah, DAMOP!

I know I said I wasn't going to post anything today, but I hadn't realized that the 2005 Nobel Prize in Physics was being announced today:

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2005 with one half to

Roy J. Glauber
Harvard University, Cambridge, MA, USA

"for his contribution to the quantum theory of optical coherence"

and one half jointly to

John L. Hall
JILA, University of Colorado and National Institute of Standards and Technology, Boulder, CO, USA and

Theodor W. Hänsch
Max-Planck-Institut für Quantenoptik, Garching and Ludwig-Maximilians-Universität, Munich, Germany

"for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique".

(Credit where due: I first saw this via Not Even Wrong.)

I'm obviously happy to see another Nobel Prize awarded in the area of lasers and quantum optics. Without getting into the merits of quantum optics relative to other fields of physics, if you're going to give the prize to people in this field, Glauber, Hall, and Hänsch are excellent choices.

I'll see if I can come up with a coherent (heh) explanation of what they did to deserve it later this week. For the moment, I need to go play with my own lasers.

Posted at 9:20 AM | link | follow-ups | 1 comment

Monday, October 03, 2005

Tuesday Basketball Post

It's Research Day tomorrow, so I'll be trying to stay away from the computer. As a result, I'll post something here that's sure to generate lots of comments: pick-up basketball observations!

We've sort of hit a bad patch in the lunchtime hoops crowd at the moment-- the students who played regularly last year all graduated, and we haven't yet gotten a new bunch to replace them (this happens every year). A couple of faculty/staff regulars have left town or been sidelined with injuries, too, so the turnout has been kind of low. We wound up playing three-on-three half-court today.

Half-court is a fundamentally different game than full-court, and stands in relation to full-court five-on-five in about the same way that three-handed Hearts does the full four-handed game. It can be fun, but it requires some significant mental and physical adjustments to play it well.

Interestingly, there are two rules differences between full-court and half-court games that come up everywhere. The less settled question is the issue of take-backs-- on a change of possession, the defensive team is often required to dribble or pass the ball back past the foul line (or three-point line, depending on what lines are on the court). Some people play that everything has to get taken back, while others hold that the ball has to hit the rim for a take-back to be necessary.

Personally, I prefer to take everything back, just because the "hit the rim" rule is generally good for two or three dumb-ass baskets a game. More if you play with really bad shooters. It's sort of the half-court equivalent of the jackass who hangs out on the offensive end when he ought to be playing defense, and then gets the long outlet pass for a cheap lay-up.

The other rule is iron-clad, in my experience: a half-court game is always presumed to be "winner's outs," namely, the team that scored gets the ball back for the next possession. I've played half-court games that weren't winner's outs, but they're rare. Everywhere I've played, winner's outs has been the rule.

As you might expect, this has a much stronger distorting effect on the game than the take-back rules-- full-court games always have the team scored upon getting the ball to start the next possession. Half-court games almost always feature huge runs-- both of the games today were even for a while, and then saw one team jump out to a 12-6 or 13-6 lead (game to fifteen), and the team taking the big lead changed from the first game to the second.

It's very easy to run off a string of made baskets, even in a full-court game. Basketball is a game of streaks, and you'll frequently hit stretches where one team scores every time down the court-- sometimes both teams will get hot. It doesn't necessarily have anything to do with defensive play, either-- sometimes, the shots just drop. In a half-court game, that sort of streak means that your opponent doesn't even get the ball, so the scores quickly become very lopsided.

When you play half-court over full-court becomes an interesting question, as well. You almost never see half-court five-on-five (it kind of sucks, because the game tends to collapse into the middle of the lane, and everything gets all jammed up), and you'll very rarely see full-court three-on-three (we'll play "full court" 3's sometimes, but always "short court," going widthwise across the main court). Four-on-four is generally a full-court game (we'll sometimes go short-court 4's, but mostly we play the full regulation court), but some people prefer it half-court.

Of course, the most annoying thing about the lousy turn-out isn't just being forced to play half-court, it's that for the past couple of weeks, I've been Michael Freakin' Jordan at lunchtime. I've had dribble moves that normally have no place in my game, and I've been absolutely nailing these ridiculous quick-release fall-away jump shots. I've even been sinking all sorts of shots while getting fouled.

This happens every now and then-- my last bizarre outbreak of game was in May of 2004-- but it never lasts long. And I hate wasting it on half-court threes...

Posted at 8:22 PM | link | follow-ups | 8 comments

The Devil Turns Soggy in Milk and Causes the Gum Disease Gingivitis

I have to admit, my first thought on hearing about Bush's choice to fill O'Connor's Supreme Court seat was "Doesn't he have a horse he could make consul, and get this out of his system?" It turns out that Miers was an even worse choice than I suspected-- the Medium Lobster has the details.

(The title has nothing to do with Miers, I just really like that sentence...)

Posted at 8:06 PM | link | follow-ups | no comments

Step One: Identify Your Audience

Fan reaction to Serenity is really feeding my contrarian impulses-- I swear, there's some sort of subliminal brainwashing thing in the Buffy DVD's. It's probably not a terribly good idea for me to really push that, though, as it could end up retroactively making me think less of the movie (which I did enjoy quite a bit while I was watching it), so let me turn to something else.

There's been a good bit of science-blogger enthusiasm over the re-launch of Seed magazine, with Clifford Johnson leading the way. People have been enthusiastic enough about it that I thought I should pick up a copy and see what I thought (I'm not cool enough to be among the science bloggers who were sent free copies). It wasn't in the first bookstore I checked (a not terribly good Barnes and Noble), but Borders had copies, so I snagged one.

My immediate reaction: Enh. It's basically Maxim for science geeks. OK, it's a little better than that, as there are at least three articles that stretch past two pages, but the emphasis is on gloss and style. (It doesn't help that some of the stylistic flourishes are things that drive me up the wall, for example, the several pages on which images are connected to their captions by fine grey lines stretching across the page.) They also try very hard to project the same sort of hipper-than-thou vibe as your typical glossy men's magazine, albeit in a geeky way.

Some of the glossy elements are fairly successful-- the feature reproducing two pages of somebody's lab notebook is kind of cool, and the various photo essays are nice. Others fall flat-- the "Force Diagram" drawing arrows on a picture of Bill Frist to represent the competing influences on him-- and at least one is actively annoying, the "Today's Vocab List" sidebar, which gives the equation for "Stoner's Excitations," and offers two definitions:

WHAT'S TAUGHT: "The ferromagnetic excitations of electron pairs in the band theory of magnetism first proposed by Edward Stoner."

WHAT WE'D PREFER: "Fantastical realizations that ultimately lead to absolutely othing; experienced by those who partake in the Rastafarian sacrament of ganja."

There aren't many levels of humor below "sophomoric." This is one of them.

Ultimately, I'm sort of confused about who they think their audience is. The feature articles seem to be roughly equivalent to Scientific American, in terms of the level of presentation, but there aren't as many of them, and the focus isn't so much on science. The hipper, glossy elements are pretty slick, but I don't know that they're slick enough to attract anybody who isn't already a confiremd science geek (also, the cover image is terrible), and again, while the pictures are very nice, there aren't really enough of them to make it work as science erotica.

The niche they appear to have in mind is, well, Chris Mooney. Not coincidentally, he has the cover story, and is apparently blogging for them, now (his earlier blog is now primarily book-tour material). You might ask why I don't link to his Seed blog, and the answer is simple: the address they give in the magazine ("") 404's. And that's probably a good metaphor for something or another.

The really critical question for a magazine like this is: Would I pay five bucks for another copy? The answer, based on this one issue, is: "Yes, if I was in an airport with a bad hangover, a two-hour flight, and nothing else to read." Which isn't glowing praise, but hey, it's better than Maxim.

Posted at 7:49 AM | link | follow-ups | 2 comments

Sunday, October 02, 2005

Don't Think About Astrophysics

They would take away my Geek Card if I didn't see Serenity on the opening weekend, so Kate and I went down to the mall and saw it earlier tonight. We ran into some colleagues in the theater, and went out for drinks afterwards, hence the late posting. I'm staying up for a bit to comfort the dog, who was semi-distraught at being left alone while we went to the movies. Emmy's a big Joss Whedon fan.

I'll keep this pretty much spoiler-free, because there's a lot to spoil. My general reaction was positive-- it's a well-paced and well-designed SF action movie, with no more Idiot Plotting than is usual for the genre (which is still a fair bit, but even the dumbest plot points aren't a patch on the stupidity of the astrophysics, about which the less said the better).

Weirdly, though, I think I would've liked it better had I never seen the original episodes. I think that, as a movie, it does a pretty good job of setting up the characters and their relationships, but it does so at the cost of making a complete hash of the series-to-movie continuity.

There are a number of problems with the transition, chief among them being the rebooting of some of the character relationships. I thought the relationship between Simon and River on the one hand and the rest of the crew on the other had pretty well been shaken out in the series, but the first bit of the movie has Mal spouting a bunch of lines that would've fit in just fine in the pilot.

There's also the fact that it's completely not clear how much time is supposed to have passed. There's one comment that has Simon and River on board for only eight months, but some of the interactions with other characters seem to suggest the passage of considerably more time.

Strangest of all, there've been a bunch of changes to the backstory, including a complete refitting of the entire Alliance fleet-- the ships they have in the movie look nothing at all like the ships from the TV series. And the Serenity itself has had some re-fitting as well, because I don't recall them carrying flying vehicles in the original. And the creepy people chasing River in the original have been replaced by one guy-- a very cool character, mind, but not one who appears to have any relationship to the original pursuers, who are completely absent from the movie.

Put all that together with some of the odd character stuff, and the movie feels less like a follow-up to the series than a weird alternate take on the same material. (Kind of like John M. Ford's The Last Hot Time compared to the Bull and Shetterly Borderlands stories.) It's good as a movie, but it doesn't quite seem to fit with what came before.

Of course, the biggest problem continues to be with the worldbuilding, which shows a great flair for design, and absolutely no concern for physics. But if I start ranting about that, I'll never get to bed.

Anyway, as I said, it's a well-done SF action movie, and there's some great snappy dialogue (other than a few absolute clunkers near the end). The plot doesn't entirely hang together, but they rarely do in such movies, and the visuals are spectacular. I'm not entirely satisfied with the way the climax worked out, but it's no worse than anything else out there. I don't think it represents a revolution in SF filmmaking, or anything like that, but it's a good example of the genre.

Just try to avoid thinking about science at any point during the proceedings.

Posted at 12:00 AM | link | follow-ups | 8 comments

ΔxΔp ≥ h / 4 π

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