Uncertain Principles

Kate and I are skipping town for a long weekend, to get a much-needed break from being on campus. This will hopefully allow me to relax and recharge just enough that I won't end up snapping at my summer students in August...

Not that anybody reads blogs on the weekend, anyway, but if you're just dying for something bloggy to read while I'm absent, there are many interesting things posted at the fine sites listed off to the left. A few particular highlights:

William Tozier at Notional Slurry has been on fire recently, with a bunch of really interesting posts. Three in particular stand out to me:

• Valuable Old Books, which raises some interesting issues about the perverse effects of bibliophilia without respect to content.
• Who Wants to Save the Great Black Swamp?, discussing some problems with the idea of restoring things to their "natural" state. This ties in with a post about the portrayal of nature in Tolkien that I keep meaning to write, but haven't. One of these days.
• What mysterious events led the Maya to leave Lorain, Ohio?, on the futility of seeking simple single explanations for great historical migrations.

All good stuff. This is why I like to read blogs written by smart people.

Elsewhere, Fred Clark of Slacktivist has a couple of posts demonstrating again why the world needs more thoughtful Christians like him. In the first, he takes up the question of what, exactly, Jesus would do (favorite anecdotal response to that question: "I know one thing he wouldn't do. He wouldn't pay ten bucks for a stupid bracelet."). In the second, he explains the deliberate badness of Christian Entertainment.

And finally, Steve Cook at Snarkout has a typically encyclopedic discussion of witch hunts through the ages. Not to mention all sorts of wonderfully odd stuff in Sideout.

There. That ought to hold the little bastards.

Posted at 6:50 AM | link | follow-ups | 1 comment

The inimitable Chun, who may be a whole lot more avoidable these days, has a post about sororities (commenting on a review of a book about sororities, actually). Amid the typically cryptic Chun comments (Hermes Trismegistus?), there was one paragraph that caught my eye:

I do believe that many graduate students and even professors probably discriminate against sorority (and fraternity, though this is a different matter) students, mostly unconsciously. Very few, if any, of our future professoriate belong to Greek organizations as undergraduates, and I suspect many form strong opinions about the vapidity of those who do. Some of this is based on simple resentment, and some is based on the natural contempt the bookish feel for those who take degrees in commerce-related areas of no apparent intellectual content.

This is certainly a hot issue on campus these days, as there are a number of changes underway that students (rightly or wrongly) perceive as an attempt by the faculty to crush Greek organizations. The dominance of fraternities and sororities in the local social scene is a perennial topic of debate locally, and probably the biggest source of friction between students and faculty.

I find myself in sort of an odd position on this issue. Chun is right that very few faculty were ever members of Greek organizations, and while I wasn't, either (Williams eliminated frats in the Sixties), the rugby club was one of the two or three most frat-like organizations on campus. Save for a few of the more ceremonial aspects, my experience of college was probably not too dissimilar to that of many of the local frat boys.

This makes a lot of the faculty talk about the Fraternity Problem and the wonders that could be achieved if only they didn't dominate the social scene kind of hard to take seriously. Some fraction of college students will always be drunken louts, whether they sport Greek letters on their clothing or not, and many of those drunken louts will turn out fine in the end. And some of our strongest students turn out to be fraternity or sorority members, so it's not like they completely squelch academic excellence.

Of course, that's not to trivialize the real problems that are caused. Fraternity pledging has a real and visible effect on many classes, with students turning up for class sleep-deprived, badly hung over, still drunk, or some linear combiantion of those. It's hard for this not to have a deleterious effect on the academic atmosphere of those classes, and I can see how dealing with this on a regular basis could turn one against those organizations.

The thing that really struck me about Chun's comment, though, was the final sentence, which has strong echoes of this ancient Making Light thread. When I read phrases like "natural contempt of the bookish," I hear myself at age thirteen or fourteen, telling myself that I'm unpopular in junior high because the other kids are just jealous that I'm smarter than they are. And, as I said in the comments to that Making Light post, I want to reach back through time and slap myself silly.

I really hope that, in those cases where I find myself taking a dim view of Greek activities, this kind of attitude isn't a part of it. To the extent that such "natural contempt" is a part of the faculty approach toward these organizations, it's a problem almost as significant as the Fraternity Problem itself.

Posted at 9:25 AM | link | follow-ups | 11 comments

The summer has officially started here, which means I'm making the transition into Research Mode. This involves a lot of sitting around while vendors don't return my phone calls, which makes my blood boil, but also the starting of a few student projects (which I'm never entirely ready for...), and revisions to a draft of a paper that we hope to send out by the end of the month.

Of course, having been in Teaching Mode for the last six months (with a brief break for DAMOP), this takes a little effort. As a way of easing the transition, and to make up for the lack of physics content here recently, I'll post a short explanation of the proposal we're writing up.

The interesting thing about this project is that it represents a collision between Big Science in the form of the CLEAN and XENON projects, and Small Science in the form of, well, me.

The Big Science here is really Big. They're talking about using large quantities of liquid noble gases (neon (Ne) for CLEAN, you can guess what's used for the XENON experiment) as a detector for either neutrinos (CLEAN) or dark matter particles (XENON). The principle is basically the same as for the Super Kamiokande detector in Japan-- once in a very great while, a weakly interacting particle from somewhere out in space will collide with an atom in the detector, and produce a flash of light. The light gets detected by phototubes, and by counting the number of particles detected, you can learn about distant astrophysical events, and test theories of how the universe works. Of course, because the events are so rare, you need to have lots of atoms for the particles to hit: one metric ton of liquid Xe for XENON, 135 metric tons of liquid Ne for CLEAN, or 50,000 tons of pure water in the Super-K detector.

The contrast between the scale on which these people work, and the scale I'm used to is perhaps best summed up by a paragraph from a paper on CLEAN:

Though this approch requires a cryogenic apparatus (the boiling temperature of neon is 27 K), this would not make the experiment overly complex or costly. For example, a commercial Gifford-McMahon cooler operating at 27 K with a cooling power of 75 W costs only $34,000.

For reference, $34,000 is roughly half of the start-up budget for my entire project.

So what can I offer to these projects? Well, the connection comes in when you start to think about the problems that affect these detectors. After all, the idea is that once in a very great while, a passing particle from out in space will interact with an atom in the detector, and make a little flash of light. These are exceedingly rare events (a few thousand per year), so you need to worry about other exceedingly rare events that might cause flashes that you would mistake for a signal.

There are a number of such processes out there, but the most pernicious from the standpoint of these experiments is the radioactive decay of krypton-85. This is a very rare isotope of krypton-- one in every forty billion natural krypton atoms is a krypton-85-- but its decay would exactly mimic the expected signal of a particle collision. In order to reach the kind of sensitivity they want, they need to limit the contamination of all isotopes of krypton in their samples of a few parts per trillion at most. That means that roughly one atom in 100,000,000,000,000,000,000,000,000 can be a Kr-85 before the background starts to become a problem.

This is, as you might expect, kind of hard to arrange. The half-life of Kr-85 (about ten years) is long enough that it's impractical to just wait it out. Krypton is a noble gas, and doesn't react with much of anything, so you can't separate it chemically. You can freeze it out of neon, but that won't work with xenon, so you have to do trickier things to get rid of the krypton. And once you do purify it, it's hard to tell how well you've done.

This is where I come in (or, rather, where the tools of atomic physics can be brought to bear). I do laser cooling, and I'm setting up a lab to laser cool krypton and argon. The basic idea of the proposal we're writing up is to use laser cooling to count how many krypton atoms there are in a given sample of ultra-pure neon or xenon.

This works because laser cooling depends very sensitively on the transition frequencies of atoms. The Doppler shifts that make laser cooling work are very small-- on the order of a few MHz in frequency units, or several parts per billion of the laser frequency. Different isotopes of the same element have transition frequencies that differ by much more than this (tens or hundreds of MHz), meaning that you can easily select out different isotopes (see for example Fig. 2 on the NIST xenon page). And different elements have transition frequencies that differ by tens of millions of MHz, so it's really easy to select out specific elements.

Laser cooling techniques are also very efficient at catching rare species. If you've got atoms of some rare isotope or rare element, you can catch them with relative ease. The coolest example of this may be the trapping and cooling of francium, a heavy element with no stable isotopes. The total amount of francium on Earth at any given instant is measured in grams, but they've been able to trap and cool enough of it to study its spectral properties. And once you've got the atoms trapped, they're easy to see, because they're constantly absorbing and re-emitting laser photons. Even a single atom can be detected with relative ease.

The extreme sensitivity of laser cooling gives rise to the idea of Atom Trap Trace Analysis (ATTA), pioneered by a group at Argonne National Lab. The abundance measurement of Kr-85 that I cited above comes from their work, and they also have one of the most dramatic demonstrations of the sensitivity of laser cooling-- between the two peaks of their Figure 4b is another isotope that is several billion times more abundant than either of the ones they measured, and it has no effect on the signal. They've used this technique for dating of groundwater samples, and have discussed its use as a means of nuclear test monitoring.

Our proposal is basically to adapt the ATTA method, which has been used to count rare isotopes of Kr in pure samples of Kr, to look for Kr atoms in a sample of Ne or Xe. At the level of purity they're looking for, this would amount to trapping one Kr atom every few hours, which is tedious, but doable. That measurement can give you the fractional abundance of Kr atoms in the gas that they're liquifying for their detectors, which can be combined with the known abundance of Kr-85 to get the background level for their detector.

So, by detecting an atom or two every few hours, with a small-scale and relatively cheap apparatus, I can provide information that will be used to determine how many of the few thousand counts a year that show up in multi-million dollar astrophysical detectors are just noise. It's amazing how Science works...

Posted at 10:50 AM | link | follow-ups | 6 comments

Josh Marshall has a couple of recent posts (one, two) about the Bush campaign's oh-so-subtle attempt to get the Vatican involved in the coming election. As Josh notes, there's some lovely irony here:

I guess on one level we can say we've come a long way since 1960 when John F. Kennedy had to foreswear that he'd follow the instructions of the Pope in his decisions of governance. Today we have a Protestant born-again who tries to enlist the Pope to intervene in an American election.

The most interesting part of this, at least for a lapsed Catholic like myself, is the question of what affect this will have on the American Church.

American Catholicisim has always seemed to be fairly distinct from what is practiced elsewhere. The first time I ran into a mention of Kennedy's Catholicism being an issue, I was sort of baffled. In my immediate family, and much of the church-going community around us, the Pope's status was less that of one of the medieval Popes, and closer to hat of the modern Queen of England: a distant sort of figurehead, whose blessing was invoked for ceremonial occasions (illuminated documents conveying Papal blessings on significant wedding anniversaries are part of the standard decor in my family), but who was generally ignored most of the rest of the time. The idea that anyone might seriously be worried that American Catholics would take orders from the Pope was too absurd to take seriously.

I'm no longer really in close contact with the Church and its current teachings-- I make it to Mass on Christmas and Easter in a good year, and for the odd family occasion. My impression from various media reports, though, is that things haven't changed all that dramatically. The Church has definitely gotten more political over the years-- explicit prayers for an end to abortion seem to be a standard part of the weekly mass these days-- but I don't get a sense that people are really paying any more attention to the various proclamations than they did in the past.

Should the Church hierarchy take up the Bush campaign's line, it'll be interesting to see whether this has a real affect on voting patterns, or whether it just further degrades the relationship between lay Catholics and the hierarchy. My guess would be the latter-- those who would've voted for Bush anyway will vote for Bush, and those who would've voted for Kerry will shrug and blow off yet another Church decree.

It's a little hard to see how this could be a net win for the Church, given that they're already having to consolidate parishes due to a lack of priests (and parishoners, to some extent). You might think that the threat of alienating even more of the liberal laity would give them pause, but then the bishops haven't exactly demonstrated a wonderful grasp of public relations in recent years, so you never know.

Of course, given the not-entirely credible claim that John Paul II thinks Bush may be the Antichrist, it might not become an issue at all...

Posted at 11:20 AM | link | follow-ups | 9 comments

A few years ago, now-- I no longer recall whether it was before or after the Florida fiasco-- my old school district had a vote on a proposal for a bond issue to build a new school building. As this came barely ten years after a major expansion of the existing school building, this was a controversial issue to say the least.

The voting, as always, was done with one of the old-fashioned lever-action voting machines. After the polls closed, the machine was opened, and the vote tallies checked: roughly 300 votes for the proposal, and roughly 200 against.

There was only one problem: 1500 people voted. The counters were set for a maximum of 999 votes, and one of the two rolled over. The results were voided, and numerous statements to the effect of "We'll never know how the voting went..." were made by school administrators (here's a hint: they never put it up for another vote...).

I was reminded of this by the ongoing discussion of voting over at Making Light. The usual suspects are there railing against electronic voting schemes, and proclaiming in advance that the fix is in.

Of course, the budget vote serves as a nice illustration that a bad system can perfectly well arise from carelessness or stupidity, rather than active malice. In the case of the budget vote, the counters were set the way they were because they had never had an election where 1500 people showed up to vote-- that's a huge percentage of the eligible voters in the district-- so it had never been an issue. They had the ability to change the counters, but nobody had ever bothered, because they didn't think it would ever become an issue. And, indeed, were it not for the "perfect storm" combination of a high turnout and a seriously lopsided vote, it never would've become an issue.

On the question of electronic voting, numerous people are absolutely floored that anyone could possibly think that electronic machines without a paper backup would be a good idea. I have absolutely no problem believing that someone would think that way, though-- all it takes is a certain all-too-common techie arrogance. It's the same mindset that brings us things an email package whose factory default setting is to automatically open attachments. What could possibly go wrong with that?

And on the question of backup, it's not like the lack of an audit trail is completely unprecedented. There was no way to recover the correct vote totals from the lever-action machine in my home town, and those things have been in use for years.

Yes, the statement by the Diebold executive who announced his intention to "deliver" votes for Bush is troubling. But buried in that long comment thread is a story of electronic glitches plaguing voting machines made by a different company. You don't need to be evil to implement the system they're talking about-- just stupid. And, similarly, the fact that you're proposing a system that might easily be manipulated does not necessarily mean that you're planning to manipulate the results-- you might just be a careless dolt. Even the refusal to change in response to criticism is as easily explained by pig-headedness as active ill will.

But then again... As Walt Pohl put it regarding a slightly different issue, in a comment over at Crooked Timber:

As a person, I'm basically anti-paranoid. I generally expect today to be like yesterday, and tomorrow to be like today. If someone had told me two years ago that the White House would order Iraqis tortured, I would have dismissed it as lefty paranoia. But now, if a lefty paranoid says "they're going to cancel the elections", I have to seriously consider the possibility that they're right. I would say that the actual chances that they would cancel the election are below 50%, but they are above zero, and that's too high.

And that's pretty much where we are right now. I deeply resent the way this administration makes the anti-paranoid feel like we have to listen to nutbar conspiracy theorists.

Posted at 12:54 PM | link | follow-ups | 3 comments

Today was the day of graduation, and after the traditional parading around to the sound of bagpipes (what is it with academia and bagpipes, anyway?), and the most solemn set of graduation speeches I've ever heard, another class was sent out into the world with spiffy new diplomas. The weather was nice (at least for those of us seated in the shady library colonnade... The students, on the other hand...), and everything went smoothly, which is about as much as you can ask for at one of these things.

It's amazing how much difference a couple of years can make. Two years ago, at my first of these, I really didn't have much stake in the ceremony. I taught mostly freshmen that year, so none of the students from my classes were graduating, and the only students I knew in the ceremony were the physics majors. This year saw the graduation of a dozen or so students I've had in class, plus a bunch of guys I played basketball with, or served on committees with, so there were a lot of people to congratulate, and a much more festive atmosphere.

Plus, we had a really solid group of majors this year-- only four of them, but four excellent students. I'm happy to see them graduate, but sad to see them go (three of them are headed directly to grad school, and the fourth is going to take a little time off). This is the last bunch of students who have been here longer than I have, and the place will seem strange without them.

Anyway, hearty congratulations and best wishes to Eric, Shaun, Jackson, and Jason. May you be successful in your future careers, and give generously to the Physics Department at your dear alma mater...

Posted at 2:20 PM | link | follow-ups | 1 comment