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Uncertain Principles

Physics, Politics, Pop Culture

Saturday, July 13, 2002

Coming in 2012: Ken Lay International Airport

In this morning's Washington Post, we find this gem:

President Bush's top official on corporate crime and responsibility was a director of a credit card company that paid more than $400 million to settle allegations of consumer and securities fraud.

Larry D. Thompson, deputy attorney general and head of a new multi-agency corporate-crime task force, was a Providian Financial Corp. board member and chairman of its audit and compliance committee from June 1997 until his unanimous confirmation by the Senate on May 10, 2001.

His defense?

Thompson did not return calls for comment. "The deputy attorney general is proud of his service on the board of Providian. He only became aware of the [fraud] issues when regulators began to make inquiries," said his spokesman, Mark Corallo.

There's also this beauty of a sentence. Bet you can't guess what the reporter's thinking:

Thompson's service on the Providian board coincided with the time regulators said Providian engaged in fraudulent conduct. Providian settled all the complaints without admitting or denying wrongdoing.

I have two immediate reactions, one more mature than the other. The more mature of the two is: "Every time I think I couldn't possibly be more disgusted by the venal and incompetent clowns running the country right now, they take it to eleven..."

The other is: "See? Positively Reagan-esque. I told you so."

(I was going to bill this as part of my substitute Jim Henley act, but Unqualified Offerings has returned, so we'll just roll with the "shrine to the ego" aspect...)

Posted at 8:59 AM | link | follow-ups | no comments

Friday, July 12, 2002

Fighting Juvenalia with Juvenalia

There's been a bunch of noise recently about Mickey Kaus's bizarre claim that the often puerile Media Whores Online site is somehow likely to incite left-wing violence. This is easily the silliest thing I've ever seen from Kaus, even though I think his claims have been somewhat distorted by most of the people taking issue with them (MWO chief among them). Their antics are a far cry from, say, Gordon "Head Shots" Liddy, and it's hard to really make a credible claim that Liddy got anybody killed (as someone emailing Ted Barlow (whose permalinks are broken) points out, Clinton's attempt to link Timothy McVeigh to Limbaugh and his ilk was approximately as goofy as Kaus's statement, as is Eric Alterman's suggestion that Anne Coulter would be in jail if she were a liberal).

All in all, I'm fairly ambivalent about outfits like Media Whores Online and the relentlessly sophomoric Warblogger Watch ("The Corndog"? Stop. Please. You're killing me. No, seriously, stop.). They're shrill and often juvenile, but they're really not much worse than The Corner (where every third post has a smirky prep-schooler sort of tone, so the whole thing reminds me of a marginally more erudite Drones Club), or about three-quarters of the people Instapundit links to. And they are at least trying to perform a useful function-- I've said for years, half-seriously, that the Democrats need a Rush Limbaugh of their very own, and damn if MWO and their ilk aren't trying to fill the role. (The current leading contender, James Carville, is a little too vaguely reptilian to really be successful...) My personal inclination would be for more civil and rational discussion, but in a world where the virulently idiotic David Horowitz is often held up as some sort of deep thinker (yes, David, we should prosecute the New York Times for espionage-- just the other day, I was saying that what this country needs is more military junta tactics...), they're probably and regrettably necessary. They're not really good at it, but that's just because American liberals lack practice at this sort of thing.

(And as long as I've mentioned Horowitz, could somebody please restrain his hands, lest he sprain something patting himself on the back for putting a Pythonesque "Help, I'm being repressed!" scam over on a few college newspaper editors? I'd be more impressed if the Holocaust deniers hadn't beaten him to the idea (they were pulling the same shtick back when I was in college)... The only interesting element of the whole sordid affair was the tantrum he threw when the Daily Princetonian handled him exactly the right way. I bet that gets glossed over in his book...)

Posted at 12:58 PM | link | follow-ups | no comments

Thursday, July 11, 2002

The Transporters Aren't Working. Again.

So, having discussed how to do "quantum teleportation," how does this get us to "Beam me up, Scotty?" Well, that's the thing. It doesn't, not in any meaningful sense. What gets "teleported" is just the state of the initial quantum particle, not the particle itself. There's no reason why you couldn't do "teleportation" with atoms instead of photons (indeed, that's the next stated goal of the experimenters in the field), but again, all you're "teleporting" is the state of the atoms, not the atoms themselves. To "teleport" a person by this method, you'd need to already have a gigantic person-sized collection of the appropriate atoms at Bob's house, and copy the quantum state of the original patron of Alice's Restaurant onto those atoms.

It's also not true that "teleportation" inherently requires the destruction of the initial object, as is sometimes claimed. For photons, this happens to be true, as most photon measuring schemes involves the destruction of the photon, but the only thing that's necessarily destroyed is the quantum state of the original. If you were to do "teleportation" of an atom, the original atom would still be sitting in the lab at the end of the experiment, it'd just be in a different state than when you started.

This is why I put "teleport" in scare quotes throughout these articles. The process is almost completely unlike what we think of as teleportation: as most people picture it, teleportation involves atoms which start out at Point A disappear from there, and re-appear at Point B. All that really moves in this scheme is information about the quantum state, and it's not even clear that that matters, as noted by an IBM researcher. (You can imagine doing the experiment with a pair of atoms in the EPR state, rather than photons, which would give you a sort of trivial motion of atoms from one place to another. The more sensible way to "teleport" atoms, however, would be to use photon pairs, entangle them with the source atom, and transfer the atomic state to another atom.) It's not without technological possibilities-- this sort of thing could have implications in quantum computing, and possibly for what Jeff Kimble at Caltech likes to call the "quantum internet," a hypothetical future network of quantum computers-- but this isn't a clear route to sci-fi matter transmission.

This is another example of good work being over-sold. I'm not claiming that the research is uninteresting, or unimportant-- these experiments are really fascinating, and add to our understanding of the weirdness at the heart of reality-- just that the terminology creates an unrealistically inflated impression of the work. It's the scientific equivalent of political spin. Calling this "teleportation" is a wonderful way to get yourself in the New York Times and on the evening news, but the word carries a host of connotations that just don't fit with the actual experiment, and those connotations lead directly to endless Star Trek references, and things like the author of the original article speculating grandly that we'll be hopping between parallel universes any day now. That sort of boundless techno-optimism is vaguely charming, but it's misplaced, due to the unfortunate terminology. The work itself is impressive enough on its own; the Star Trek stuff is gilding a lily that, scientifically, doesn't need the help.

To their credit, most of the scientists involved try to distance themselves from such claims (some more emphatically than others, but they all at least hedge their bets). The problem is that the unfortunate name given to the process plants the idea in the minds of techno-enthusiasts and "futurists," and sticks the rest of us with dealing with the connotations and Star Trek questions.

(I should note that there are plenty of other problems with the Vegas article. The (sketchy) description of the process is slightly garbled in a manner that suggests the author is more a techno-enthusiast "nerd groupie" than an actual nerd. I don't want to give the impression that it's a good explanation of the issues involved-- most of the other links I've provided above and below do a better job. The Vegas City Life article happened to start me thinking about this stuff, leading to these posts, and that's all.)

Posted at 10:38 AM | link | follow-ups | 3 comments

Beam Me a Photon, Scotty

So, the last whopping huge physics post here covered the idea of quantum entanglement-- how do you get from entanglement to "quantum teleportation", which is what the article that kicked the whole thing off was about?

The first step here is to define what's meant by "teleportation" in this context. The idea here is that you've got one person, traditionally called "Alice" who has a quantum particle (we'll say it's a photon, to be concrete). She wants to get the photon to a second person, traditionally called "Bob," who needs it as part of a scheme for world domination, or something. It's critically important that Bob end up with a photon in exactly the same quantum state as the one Alice starts with, and for some reason that's never adequately explained, Alice can't just send him the actual photon she's got.

"Well, the answer is simple," you say, "she just measures the state, and sends Bob that information, and he can generate a photon on his end, and put it in the right state." Unfortunately, quantum mechanics doesn't work that way-- it's impossible to do a complete measurement of the quantum state of a single particle.

That's a little strange, right there, so I'll unpack it a little. To be concrete, we'll deal with horizontal and vertical polarization states again. If Alice's photon is exactly horizontally polarized, or exactly vertically polarized, there's no problem-- she can simply measure the polarization and report it to Bob. But Alice doesn't know what the state is-- it could be anything. Therefore, quantum mechanically speaking, it's some combination of horizontal and vertical polarizations. Again, in the interest of being as concrete as possible, let's say it's a 50:50 mix-- it's simultaneously both horizontally polarized and vertically polarized, and an equal mix of the two-- mathematically, we'd say the state is "H + V".

When Alice tries to measure the polarization state, she's essentially asking "Are you vertical?" of the photon. If the photon were exactly vertically polarized, the answer would always be "yes"; if the photon were exactly horizontally polarized, the answer would always be "no." For a photon in a superposition state, like the "H + V" photon mentioned above, the answer could be either. 50% of the time (completely randomly-- God, having grown tired of dice, flips a coin, and "heads" is "yes"), the answer will be "yes," and the other 50% of the time, the answer is "no." If you did the measurement on a hundred identical photons, you'd get (on average) fifty vertical and fifty horizontal photons; for any single photon, you'll randomly find one or the other.

Here's the tricky bit, though: after a measurement where the photon is found to be vertical, the photon will be vertically polarized, and only vertically polarized. If she tries to do a second measurement asking whether it's horizontal, the answer will always come back "no." Similarly, if her original inquiry about whether the photon is vertically polarized comes back "no," the photon is instantly and absolutely horizontally polarized, and a second measurement will always find it to be horizontal.You can't detect a photon state of "H + V" by first measuring "H" and then measuring "V"-- after the first measurement, the superposition state is destroyed, and the state is definitely and absolutely one or the other.

So, Alice sends a message to Bob saying "vertical", he sets his photon generator to "V", and he scheme for world domination fails, because he's failed to duplicate the original "H + V" state. The same thing happens if Alice detects a horizontal polarization-- after the measurement, her photon is in the "H" state, and Bob's out of luck, because he doesn't end up with "H + V." (It's not as obvious, but the same problem occurs if Alice tries to get clever and asks "Are you H + V?" of a pure vertical photon. Trust me.)

Essentially the situation is the same as with Schroedinger's hapless cat. Before the box is opened, the cat is both alive and dead at the same time, but once you open the box, it's either alive, or it's dead, and there's no going back to the original indeterminate state. What Bob wants is the indeterminate state-- he wants the cat to be both dead and alive when it gets to him-- so it's vitally important that Alice not "open the box" by measuring the photon state.

So how do you get around this problem? The answer is "quantum teleportation," the brainchild of a group of scientists working with Charles Bennett at IBM (Interesting side note: The guy in the middle of the back row in the group photo, Bill Wootters, taught my undergraduate Statistical Mechanics class). The key to the idea is to use the magic of quantum entanglement to transmit the state from Alice to Bob.

Alice, being a clever student of physics, gets herself a system that generates entangled two-photon states-- those "HV + VH" states I talked about last time, colloquially known as "EPR Pairs." She sends one of the two photons to Bob, and keeps the other one for herself. The state of the EPR photons is indeterminate, but she knows that whatever the polarization of her photon is, Bob's photon is the opposite. She's also got a photon of indeterminate polarization that she needs to send to Bob.

The clever trick is this: To "teleport" the unknown photon state to Bob, she makes a joint measurement on both of the two photons she has. She doesn't measure the individual states, but measures some relative property of the two. One way to do it would be to do a measurement to see if the two photons have the same polarization-- not what that polarization is, just whether they're the same or different. (The details of how to do this are a little tricky, but you can set up something that basically does the right thing) Doing this causes the state of the EPR pair to become entangled with the state of the photon she's trying to send to Bob-- if the two are the same, then Bob's photon is the opposite polarization of the one she's trying to send; if they're opposite, then Bob's photon is in exactly the state he's looking for. This happens instantaneously, via the "spooky interaction at a distance" that bothered Einstein so much. All she has to do now is send Bob the result of her measurement-- if the two photons were the same, then Bob rotates his photon's polarization by ninety degrees (changing horizontal to vertical); if they were different, then he does nothing. After that, nothing can stop Bob from taking over the world.

There are a few subtle quirky things about this that are worth mentioning: one is that the state moves from Alice to Bob without either of them ever having the slightest idea what it is. This is a very non-classical sort of operation. Another important quirk is that the process destroys the initial state-- it may not necessarily destroy the initial photon, but the state is necessarily changed in making the entangling measurement. Bob gets a perfect copy of the state that Alice started with, but Alice is left with (at best) a photon in a different state than she started with. "Quantum teleportation" is analogous to having Alice send Bob a fax, where she's not allowed to read what's on the paper, and the fax machine shreds it immediately after sending it. (As opposed to the usual state of affairs, where I write down an order, read it over, then fax it to an electronics vendor, where they shred it, leaving me with a perfectly readable copy, and them with no trace of the order...)

It's also important to note that no useful information is sent faster than light-- Bob's photon changes its state instantaneously, but until he gets the message from Alice telling him what she measured, he doesn't know whether he has the right state, or a state that's ninety degrees off. Alice's message has to go via classical channels, and can't travel any faster than the speed of light.

There have been a number of experiments done to verify that this scheme works. Single-photon states were "teleported" by a research group in Austria. With a little bit of work, you can extend the process to include states with large numbers of photons-- laser beams, for example-- and more information than just polarization states, but the basic idea is the same. The first experiment on laser teleportation was done in 1998 by a group at Caltech (with collaborators from all over the place). The Australian results mentioned in the article which kicked all this off (more comprehensibly explained in this New Scientist article-- they have a general teleportation article as well) are essentially a refinement of the Caltech experiment, using better lasers, and doing a slightly better job of conveying the state across the lab.

So what does this have to do with Star Trek? I'll talk about that in a separate post.

Posted at 9:40 AM | link | follow-ups | no comments

Wednesday, July 10, 2002

Department of Shameless Self-Promotion

As long as I'm posting a whole bunch of stuff, I'll note that there's a new post on my book log, reviewing Alex Irvine's A Scattering of Jades.

I'm done now. Really.

Posted at 10:24 AM | link | follow-ups | no comments

Spooky Interaction at a Distance

Yet again, SciTech Daily provides me with weblog material, this time in the form of an oddball article in the Las Vegas City Life archives (how do they find this stuff? It never would've occurred to me to look there...). The article is mostly about the perils of futurism, but the new development which sparks the article, and caught my eye, is a "quantum teleportation" experiment done at the Australia National University (Important Caveat: There's a tempting link in the upper left-hand corner of that page which promises a "Simple explanation of quantum teleportation." This leads to a 2.5 MB PDF file, which may or may not be simple, but definitely takes a long goddamn time to download. There's also a press release about the work, which is thoroughly uninformative, but does have a really cute chip-on-shoulder moment when it proclaims that the work "is ahead of similar efforts in Europe, Japan and the US; and demonstrates that truly world leading research is possible in Australia - if imagination, financial support and perseverance can be combined and nurtured.").

(Actually, what really caught my eye about the article from Vegas was the suggestion that one goal of the experiment was "getting every researcher involved in the project wildly fucked by nerd groupies." As one who has formally forsaken any involvement with nerd groupies (on advice of counsel, I should emphatically state that Kate is not a "nerd groupie"), I must say that I'm shocked-- shocked!-- at the idea that such work would be motivated by anything less than pure scientific curiosity. Well, mostly I'm shocked by the idea that they have nerd groupies in Australia (that's what I get for going to grad school in Maryland-- all they have in the D of C is political groupies), but I digress...).

The key idea in "quantum teleportation" is entanglement. I've mentioned this before, when talking about quantum computing, but it's worth going over again. As with the quantum computing posts, this will take enough set-up (I need to explain the "EPR Paradox" to explain how "teleportation" works) that the actual material about "teleportation" (and maybe a bit of ranting) will appear tomorrow.

Say you've got two quantum objects-- call them photons, to be concrete-- each of which has two possible states-- horizontally polarized or vertically polarized, for example. (Real photons can have polarizations at arbitrary angles, but you can thing of those as being a mixture of different amounts of horizontal and vertical polarization, so "H" and "V" are sufficient to describe the problem.) There are four possible states the two-photon system can be in: both horizontal (HH), both vertical (VV), or two possible states with one horizontal and one vertical (HV and VH). In general, until you make a measurement of the state, it's in a superposition of all four possible states at once: HH + VV + HV + VH. This is sort of a weird state of affairs, but once you get past the problem with the superposition of states (no small trick), it's a pretty mundane state. The states of the two photons are independent of one another-- If you measure one of them to be vertical, you're equally likely to find the other polarized vertically or horizontally. (You can think of it like a coin toss, if you like, with "H" being heads, and "V" being tails.)

However, imagine that you can do something to the system so that the states are no longer independent-- in laser experiments, this is generally accomplished by using special crystals that spit out two photons when struck by laser light, with a very specific relationship between the polarizations of the outgoing photons. The details don't really matter, what matters is that the end result is a state where the photon polarizations are correlated. If one is horizontal, the other is vertical, and vice versa. Until you make the measurement, the system is still in a superposition state, but now there are only two possible states in the superposition: HV + VH.

"Big deal," you say, casually. It doesn't sound that surprising, really, but it's an exceedingly troublesome idea: Imagine taking the two photons, and shooting them off into space in opposite directions. Let them travel for, say, a year before you measure the state of either. At this point, they're two light-years apart-- something like twelve trillion miles. Now, imagine that you have some space alien friends with really good clocks sitting out there waiting for the two photons. Alien A measures one of the two exactly one year after it was sent out, and Alien B measures the other exactly one year and one nanosecond after it was sent out. If they get together afterwards, and compare results, they'll find that their measurements are exactly and absolutely correlated-- if A finds horizontal polarization, B will find vertical, and if A finds vertical, B will find horizontal. You can repeat the experiment a million times, and every time the two will have opposite polarizations.

"Big deal," you say again. "That's the way we set it up-- when they left the crystal, one was vertical and the other was horizontal." But that's not how it works. According to quantum mechanics, the state is indeterminate until the measurement occurs. Until A measures the state of that first photon, the system is simultaneously in both HV and VH. The instant that A makes the measurement, though, the state of both photons is determined. Which means that, somehow, photon B has to know that photon A was just measured. But they're two light years apart, and B was measured a nanosecond after A-- a signal from A to B saying "I was measured! You're horizontal!" would need to travel at 18,840,000,000,000,000,000,000,000 times the speed of light, which is ridiculous.

This bothered Albert Einstein to no end-- after all, his claim to fame was proving that light speed was an absolute upper limit. The thought experiment described above (in slightly different form) was first posed as a paradox by Einstein, Boris Podolsky, and Nathan Rosen, as a counter-argument to disprove quantum mechanics. Einstein famously referred to the connection between the two particles as a "spooky interaction at a distance" (which is a great phrase, probably one honkin' big word in German, and really ought to be appropriated as a description of Usenet newsgroups or weblogs...). This gedankenexperiment (another great German word) is known as the "EPR Paradox" in honor of the three authors of the original paper.

(One of the great ironies of the history of quantum mechanics is that Einstein's work is one of the major pillars on which QM rests, and yet he himself found the theory philosophically distasteful, and spent his later years trying to find a replacement for it. He's famously quoted as saying saying "I cannot believe that God would choose to play dice with the universe." Only slightly less well known is this rebuttal from Pratchett and Gaiman's Good Omens: "God does not play dice with the universe; He plays an ineffable game of his own devising, which might be compared, from the perspective of the players (i.e., everybody), to being involved in an obscure and complex version of poker in a pitch-dark room, with blank cards, for infinite stakes, with a Dealer who won't tell you the rules, and who smiles all the time.")

In order to get out of the EPR paradox, you need to do one of two things-- either you need to sacrifice the indeterminacy of quantum mechanics, and develop a new theory in which the states of the individual particles are well defined through the whole experiment, even if they're not known to the experimenters (such theories are called "hidden variables" theories, and that's pretty much what Einstein was angling for); or, you have to sacrifice the whole idea of "locality," the idea that particles are in specific places, and their properties are determined in those places-- in essence, you have to say that the two photons are actually a single quantum system, even though they're twelve trillion miles apart. Throwing away locality requires you to accept (paraphrasing an old textbook of mine) that the result of a random process occurring in one place can affect the result of another random process occurring at the same time in another place. Neither of these choices is particularly appealing, and it's not immediately obvious how to distinguish between them.

In 1964, however, John Bell proposed an ingenious experiment which could distinguish between hidden-variables theories and non-local theories. In particular, he was able to show that the results of a certain set of measurements had to satisfy a certain inequality for any conceivable hidden-variable theory. If Bell's Inequality is satisfied (or violated, depending on how you look at it), then there is no possible way to explain the results with a hidden-variables theory, and locality goes out the window. The first experimental tests of Bell's Inequality were done by Alain Aspect and co-workers in 1982, and showed fairly conclusively that locality had to go. There are still people who argue that the experiments haven't completely ruled out all counter-arguments, but most physicists regard this as a settled issue. Einstein was wrong, quantum mechanics holds up, and we live in a non-local world. (Explaining the details of Bell's Inequality and the various debates about it is a topic for another post-- if you're interested, here's a concise formal summary from a few years back, or you can Google on "Bell's Inequality" and "EPR Paradox" for a wealth of other material).

This business of non-locality is another example of the deep and fundamental weirdness of quantum mechanics. It's yet another pillar of the classical philosophical picture of science that had to be cast down to deal with a quantum world, and it doesn't fall easily. We like the idea of locality-- it makes life much simpler.

Happily, as with most of the other weird features of QM, non-locality and EPR states also turn out to open the way for interesting technological applications, particularly in what's known as "quantum cryptography" (which I'll talk about another time). These are also what make "quantum teleportation" work, but I've nattered on for rather a long time already, so we'll save that for tomorrow, along with a bit of a rant about the over-selling of some experiments and the perils of science by press release.

Posted at 10:06 AM | link | follow-ups | 1 comment

Get Your Substitute Unqualified Offerings Here...

An unintentionally humorous Instapundit moment:

I MISSED THE WHOLE HARKEN FLAP last week, and I'm still not clear what it was about. But this post suggests why it's already died down.

The link 404's. Yeah, it's just the Blogspot Archive Bug (it's not hard to find the post he's trying to refer to, but hardly worth the bother), but I like the 404 as a sort of statement that the issue hasn't actually died down, but just can't penetrate the meter-thick baffles of willful ignorance protecting the Offical Blogosphere Echo Chamber...

(Yeah, fine, it's a cheap shot. It's also not especially Henley-esque. There's a big long post about quantum mechanics coming, let me have a little fun...)

Posted at 10:00 AM | link | follow-ups | no comments

Tuesday, July 09, 2002

Lies and Damned Lies

It's been a rough couple of months for the New York State Education Department. First they get slammed for their bowdlerized Regents Exam in English, and now they're taking heat for the "too-hard" physics exam (stories about the problem have appeared in the New York Times and New York Post). This one's particularly depressing, and not just because I can probably expect to have some of these students complaining about my grading next year...

As a discipline, physicists tend to pride ourselves on our grasp of statistics-- maybe not the high-level statistical arcana understood by mathematicians and people at the census bureau, but on a common-sense sort of level. Given that no experiment is ever perfect, and random errors are inescapable, the progress of science is necessarily a statistical process-- you can make statements about uncertainties, and confidence levels, and the statistical probability that your results are correct, but never attain absolute graven-in-stone TRVTH. Understanding and interpreting new results in physics requires a good grounding in statistical matters-- given some number of data points, how many do you expect to fall outside the error bars? how much confidence can you have in extrapolating from that sample to a general rule? what sort of deviation from a prediction do you need to have for that deviation to be significant?

This familiarity with error and uncertainty has allowed the field to produce some great debunkers of pseudo-science-- Bob Park of the University of Maryland and the American Physical Society is one of the best, and his What's New feature (linked over on the left) is a good source of material about foolishness and fraud in science and science policy. (Wandering even farther afield, I'll note that one of the most entertaining and informative conference sessions I attended at the APS's Centennial Meeting in Atlanta was the "kook session" in which Park and the great James Randi held forth on various flavors of pseudo-scientific idiocy, mostly in medicine, which is something of a target-rich environment for satire or moral outrage, whichever you prefer...). Robert Ehrlich's Nine Crazy Ideas in Science is also a worthy entry in the canon, doing a nice job pointing out statistical chicanery in a couple of high-profile cases. Physicists are also prize the ability to make back-of-the-envelope estimates, and do simple common-sense analyses and experiments on the fly-- the most famous example being Feynman's performance at the hearings about the Challenger disaster.

That's why it's especially depressing to see a physics teacher complaining to the New York Post that one of his students got a raw score of 68 (i.e. 68 percent of the questions were answered correctly) and had that scaled down to a grade of 65 (out of 100). Yes? And? 65 and 68 are not so different, and as I keep having to remind students, grading on a curve doesn't mean that everybody's grades will go up.

On the web site linked above, the state provides a very detailed explanation of the grading, and the changes in the test format (PDF file of the release). This all seems perfectly reasonable to me-- as they rightly note, some questions are easier than others, and it's not right for those to be given the same weight as more challenging questions.

The biggest change in the format is also a sensible one-- in previous years, students have been able to choose from a set of "blocks" of questions about various topics. Thus, it would be possible, in principle, for a student to score 100% without knowing a thing about Solid State Physics. While this format tends to be popular with students (I had several requests for it in classes this year), it's not really right-- if you're going to test knowledge of the material, you need to test on all the material. The optional blocks of multiple-choice questions were eliminated this year, in favor of more "extended answer" questions. In my opinion, this is a positive move-- multiple-choice questions are a reasonable way to test basic conceptual understanding, but you need to pose actual problems if you want to know whether someone really understands the material.

The fundamental problem here is that high scores have come to be viewed as an entitlement, not an achievement. Physics is a hard subject, and a fair test of the students' real understanding of the material isn't likely to find 33% of the students scoring between 85 and 100, as in past years. This year's figure of 16% sounds a whole lot more reasonable-- it might be on the short side, but not by a factor of two (I've had 11% of students score above 85% on the final exam over the past two terms of introductory college physics, though those were admittedly very tough exams). A 33% failure rate is high, but probably not a wildly inaccurate assessment of their actual knowledge.

Unfortunately, students and parents aren't after accuracy, they're after high grades and positive feelings. And all too many teachers go along with them.

Posted at 11:41 AM | link | follow-ups | no comments

Monday, July 08, 2002

Hey, Ref!

I've just been asked to referee a journal article, for the fourth time in the last seven months. Since "peer review" is often cited as the cornerstone of modern scientific research, and since most people probably don't have a clear idea of what's involved, and since blogging about it is a convenient way to procrastinate my way out of actually reading the paper in question, I'll talk about the peer review process a little bit.

The basic idea, found in any philosophy of science textbook, review of Stephen Wolfram's new book, or rant against "Intelligent Design" theory is that science advances toward the truth through a process of tests and verification. New results by a particular research group are submitted to the larger scientific community, described in enough detail for other researchers to be able to check the validity of the work and attempt to duplicate the results. If new experimental results are repeatable, or new theoretical predictions are confirmed by experiment, those results will gain acceptance, and form the basis for the next incremental step forward. Peer review, the initial vetting of submitted papers by qualified scientists which takes place before publication of a journal article, is one of the cornerstones of this process.

The reality of the process is, of course, a little messier. The way the process works in practice, from the author's point of view, is that you pour sweat and blood and tears into crafting a concise but complete description of your work, which you ship off to a journal, who sends it out to some anonymous reviewers (usually two of them), who spend the next six weeks ignoring the paper and the badgering notes sent to them by the journal editors, then callously rip your work to shreds and insist that you make major changes that push the paper over the journal's length limits, leading to a big fight with the editors.

From the referee's point of view, of course, this looks completely different. As a referee, the way the system works is that the journals wait until you're out of town for some rest and relaxation, then email you a note saying "We'd like you to review this paper. If you don't respond in the next fifteen minutes, we'll assume you agree, and send you the article." By the time you get back, you're implicitly committed to reading some inscrutable gibberish from a field you've never worked in, which was originally written in Chinese before being translated into Portugese, then Pashto, then Finnish, and finally into English via the Babel Fish. You're teaching four classes, writing a paper for another journal, and you've been called for jury duty on a capital murder case and sequestered, so you put off reading the paper for a little while, only to get a barrage of nasty letters asking when they can expect your report. Then, when you do submit a report ("Please, please, please, ask a native speaker of English to proofread this for you."), the authors have the temerity to take issue with your carefully constructed comments.

OK, so maybe that's slightly exaggerated.

The way it works is that a paper presenting new results is sent to a journal, where the editors check it quickly for general suitability (i.e, they make sure that it deals with physics rather than political sciecne), then send it out to two referees, chosen from a pool of people whose names, addresses, and areas of expertise are kept on file at the journal (these, in turn, are drawn from the people who've published papers in that journal in the past). The referees are asked to read the paper, and judge the quality of the science: is it original work, is it factually correct (or at least plausibly so), does it provide all the necessary details, does it generally increase the store of human knowledge? Referees also make recommendations based on the form of the paper-- is the writing clear and are the figures comprehensible?-- and depending on the journal may be asked to make judgements on more nebulous criteria like "importance in its field" or "general interest." Based on the comments of the referees (who remain anonymous to the authors), the paper can be accepted immediately, rejected outright, or sent back to the authors, with the comments attached, for whatever revisions are needed to make it acceptable.

As indicated by the exaggerated descriptions above, this is a gigantic hassle for everyone. Papers in the more important journals (Science, Nature and Physical Review Letters) are subject to very strict length limits, so it's not always easy for the authors to make the changes, and scientists are a prickly bunch when it comes to outsiders criticizing their work, so referee comments can lead to big fights. On the referee's side, reading a paper closely enough to make the necessary comments is incredibly time-consuming-- it's not quite as bad as the "source cite" process student law journals use (mostly due to the lack of free student labor to check the fiddly little details of the formatting), but getting enough of a picture of a slightly foreign field to be able to place the paper in context and jdge its importance takes a bit of work (though it often turns out to be rewarding). Additionally, the length constraints tend to force a terse and jargon-laden writing style that can be difficult to decipher (but easy to parody), even for a trained professional. In general, authors submitting papers tend to regard the process as one of those pain in the ass things that you just have to get through by whatever means necessary (sort of like meeting the seemingly arbitrary formatting requirements most journals set), while people tapped to referee papers try to get out of it whenever possible, by passing the papers off to colleagues, post-docs, or grad students.

Hassle aside, though, it is a critical part of what makes things work. It's what separates the Intelligent Design crowd and the Time Cube guy from actual scientists, and the process does work. In the handful of papers I've published, one referee caught an embarassing typo in an equation that had somehow slipped past the five authors, while another asked a very good question which later came up during my PhD defense (not an event which really changed the history of science, I suppose, but I felt a lot better for knowing the answer beforehand...). One of the papers I've refereed had a sign error in the very first equation, which changed everything that followed (they didn't make it into print). This knowledge of the importance of the task is pretty much the only thing that keeps the system working-- referees aren't paid for their time, and it's very much a thankless job, but I try not to turn down requests to referee papers unless I'm really not qualified to comment on the work in question, just because somebody has to do it, and it's an important part of scientific citizenship (basically, it's the science equivalent of jury duty).

The biggest problem with the system is that the criteria for publication can become ridiculously variable. One referee's idea of "important and of general interest to the physics community" may be another's "uninteresting crap." I hardly ever read Physical Review Letters without thinking "who the hell thought this was important enough to publish here?" and many an author has suffered rejection from a major journal only to look in the next issue and find essentially identical work with a slightly different spin. There are some safeguards built into the system to prevent political crap (authors can suggest referees, and request that some people not be given the paper to review, and journals try to avoid sending papers to close colleagues), but accusations that so-and-so spiked a competitor's work as a referee are a staple of ugly physics gossip. I've had the good fortune to work in a field where there's relatively little riding on any individual publication, but I've heard horror stories from other fields about authors deliberately leaving out or falsifying critical information to protect a competitive advantage or patent bid (Derek Lowe would be the guy to ask about that).

Still, for all its ungainly aspects, it's a far cry from the extreme Kuhnist/ post-whateverist picture of science as "socially constructed." There are ugly controversies from time to time, and a little bit of "grade inflation" as the standards for importance and general interest seem to be slipping, but by and large the system works. Blatantly incorrect work gets weeded out, basically correct but badly written work gets whipped into slightly better shape, and Science, as they say, Marches On. The proof is all around us-- peer review is essential to the progress of science, and the progress of science has led to the dizzying array of technological conveniences that make everyday life bearable.

To paraphrase a famous quote about democracy, the current system is the worst system except for every other method that you can think of. It's inelegant and inconvenient, and the subject of frequent hand-wringing pieces about how everything's falling apart, but somehow or another it hangs together well enough to make everything else work.

Posted at 10:31 AM | link | follow-ups | 7 comments

Sunday, July 07, 2002

Tell Us What You Really Think

"If you put a million monkeys without diapers in a room filled with word processors, surely it wouldn't be long before they produced a book better than this one."
--David Futrelle, reviewing Small Pieces Loosely Joined: A Unified Theory of the Web by David Weinberger, in the Washington Post's Book World.

Posted at 10:54 AM | link | follow-ups | no comments

The Path of Least Effort

The other comment I wanted to make regards a slightly earlier paragraph in the Den Beste article commented on below:

If there's any single factor which correlates most strongly with how well any given kid maximizes his potential (though not with how he does absolutely on achievement tests), it's in how much commitment his parents have to trying to make sure he does well in school. The biggest reason vouchers may well make a difference is that they may tend to motivate more parents to become more concerned about their kids education, instead of fatalistically accepting a terrible result.

That's actually a fairly reasonable point. I'm not sure I have any real confidence in this, though, based on what I hear from voucher proponents. In an ideal world, the effect would be to make parents take a greater interest in the education of their children, but I'm not convinced that the interest, in reality, will go beyond the absolute minimum level. What I really expect is more along the lines of "the public school sucks, we're sending you to Catholic school" followed by a resumption of the previous laissez-faire policies.

This is the real core of my objection to vouchers: it's just the latest in a long series of quick-fix schemes (assuming that it's not just a disguised subsidy for people already sending their kids to private schools, as Matthew Yglesias speculates (you'll need to scroll down to find the post, as his perma-links are all screwed up-- apparently, this is endemic to BlogSpot. If I figure out how to fix it on my end, I will, but you could do worse than to poke around his weblog for a while)). The goal of vouchers isn't actually an improvement in the education system, it's an improvement in the education system without any special effort on the part of parents and politicians. The central conceit of vouchers is that by running the public schools through the Magic Black Box of private enterprise and the free market, the system will effortlessly repair itself.

If you really believe that, I know some nice people in Nigeria who'd like to launder a trillion dollars through your bank account. Education is not a simple process, and fixing the school system is not a simple problem. Getting the best possible education for your child requires a degree of involvement significantly beyond the simple signing of tuition checks. It requires showing up at school for purposes other than picking up, dropping off, and bitching about grades or discipline. It requires sending a message to children that education is important, by taking an interest in what your child is doing in school, and by encouraging any interests they have. It requires proper funding for the schools, and seeing to it that the funding is allocated in a sensible manner-- doubling the athletic budget can't be expected to improve test scores, and adding four new administrative departments isn't likely to help, either.

With an appropriate level of parental involvement and encouragement, it's perfectly possible to get a good education even from a mediocre public school-- I'd count myself as an example of that. Were more parents to take a positive interest in the public school system, we wouldn't need to be having this argument.

It's also perfectly possible to send a child through the very best private schools the nation has to offer, and still end up with a complete chucklehead. Examples of this abound. Private schools without parental involvement are no panacea-- the central failure of the voucher movement is the assumption that they are.

Posted at 10:16 AM | link | follow-ups | no comments

Tenure: Threat or Menace?

Toward the end of a surprisingly sensible discussion of vouchers, Steven "Triage" Den Beste writes:

It also may induce a certain darwinism into the school system. It may, at last, be the answer to tenure. If the worst teachers are segregated into a school which fails, then they can be terminated when the school is closed outright without violating their tenure rights. Then the average competence of the teachers in the district rises. But it's an expensive, slow and extremely inefficient way to weed out the worst teachers. (IMHO, tenure is the absolute worst thing that ever happened to the educational system in the US at all levels, from kindergarten all the way up to post-graduate study. If everyone is paid according to seniority, and if no-one can ever be fired, what is to keep someone from just coasting?)

School vouchers is one of those issues I try fairly hard to avoid getting sucked into debating (with limited success). It's not that I don't have an opinion on the subject (as should be obvious from a previous post), but rather that my opinion is a bit too strong, and too bound up in personal stuff, for civil debate. My father just retired after thirty-two years of teaching sixth grade in a public school in a rural area of New York State, and for many of those years he was an active member of the teachers' union in the district. This means that the terms of the debate as set by most right-wing voucher proponents (that public schools are unremittingly awful, that teachers are venal and lazy, that teachers' unions are the servants of Satan) tend to strike me as personal insults, and I have to work hard not to get personally insulting in return.

With that warning out of the way, I have a couple of comments on Den Beste's comments above (which I'll split into two posts). In particular, I want to note that they reflect a couple of very common misconceptions about the tenure system and what it's for. (Full disclosure: Not only am I biased in favor of public school teachers in general, I'm also an assistant professor in a tenure-track job, so I have some interest in the system as it currently exists...)

First of all, tenure does not mean that it's simply impossible to fire anybody. It makes it more difficult to fire somebody, but it's possible to fire a tenured individual, given sufficient cause. Firing a tenured individual is a time-consuming process, and will almost certainly involve lawyers, but given careful documentation of the problems leading to the firing, it can be done. "We can't fire him, he's got tenure" is administrator-speak for "we don't want the hassle." The inviolability of tenure is as much a matter of administrative convenience as a structural reality.

But why have it at all, particularly in the public schools? The fact is that education, more than any other business, sometimes requires pissing people off. People generally seem to buy this idea on the college level, but it applies just as well at lower levels. I'm not just talking about McCarthyite political witch hunts, here-- try to imagine being a high-school biology teacher in the Bible Belt. The goal of education is to provide students with an accurate picture of the current state of our knowledge of the world, and that will sometimes require direct challenges to deeply held beliefs. Tenure protects biologists from being run off for failing to embrace young-Earth creationism, health teachers from being chased out for providing accurate sex-ed information, English teachers from being ridden out of town on a rail for assigning The Adventures of Huckleberry Finn.

It's also a protection for classroom discipline, particularly against parents. This may seem somewhat odd, given that most educators complain about a lack of parental involvement, but the real problem is often an excess of the wrong sort of parental involvement. Troublemaking students are often the spawn of parents who insist that little Johnny is an angel at home, and couldn't possibly be causing problems in school, so the teachers must be out to get him. Those people can already wield disproportionate power over gun-shy administrators by hinting at the possibility of lawsuits (I could generate a hundred megabytes worth of examples on this sort of thing without scratching the surface of my father's collection of anecdotes)-- if the teachers' jobs were also on the line, things would be much worse.

What about the issue of "coasting"? First of all, it's not true that tenure and "merit pay" are fundamentally incompatible-- the school where I presently work has both tenure for senior faculty and an extensive merit pay system. It's a very complicated process, requiring a detailed review of the activities of every professor over the course of a year, but everybody seems to agree that it works. Other than the difficulty of doing a fair review, and comparing across disciplines and grade levels, I'd have no objection to a system to reward good teachers beyond a seniority-based pay scale.

More importantly, though, it takes years to get tenure-- generally somewhere in the neighborhood of six or seven years. This is not a privilege that's granted lightly. Those are six or seven years during which the teacher doesn't get to "coast," six or seven years during which the school can evaluate them thoroughly to make sure they're competent, six or seven years during which they can be fired with relative ease should any problem come up.

If you can't manage to weed out the incompetents and people likely to start "coasting" during that span, well, you don't deserve to be running a McDonald's, let alone a public school. OK, fine, there's no guarantee that they won't go nuts or start "coasting" twenty years down the line. But while everybody can think of an example of a teacher who appeared to be just marking time until retirement, the majority of teachers don't do this. If nothing else, the nature of the job tends to drive out people who don't actually want to be there, doing what they're doing.

Posted at 10:07 AM | link | follow-ups | no comments

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