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Uncertain Principles

Physics, Politics, Pop Culture

Saturday, May 01, 2004

Crucial Parenting Advice, and Cat Vacuuming

There are a lot of blogs out there writing a lot of good stuff, and my job keeps me busy enough that I don't read more than a tiny fraction of them. I don't even read everything that's over on the left sidebar on a regular basis-- some of them don't update frequently enough to be worth daily checking, while with others, I got out of the habit of checking during an earlier hiatus, and have just never gotten back into the habit.

There's another big class of blogs out there that I see links to on a regular basis, but don't link to myself. And whenever I follow a link to one of these sites, I like what I find, and say to myself "Why don't you link to this person?" The answer is always the same: "Because I'm too lazy to update the blog template, that's why."

John Scalzi is one of the prime examples of this. I get directed there reasonably often, and I always enjoy it, but he's never quite managed to spur me to add him to the sidebar. Until now, because I can't not link someone who wrote this sentence: "I think that one of a parent's more minor but nevertheless important responsibilities is to make sure his children grow up with a love of music that doesn't totally suck." Amen, hallelujah. It seems like a decent mix CD, too.

So "Whatever" joins the links to the left (insert your own Ben Folds joke). While I'm at it, I've added a few other links: Electron Blue which provides an interesting perspective on learning science to complement the teaching and research blogs already on the list; Chris C. Mooney, who works overtime exposing bad science; and Billmon's Whiskey Bar, which has nothing to do with science, but elevates quote collection to an art form.

Posted at 8:18 AM | link | follow-ups | no comments

Thursday, April 29, 2004

Stronger Than Old Hapless Gods

In the very nice comment thread that's sprung up around the last post (this is why I envy Teresa Nielsen Hayden), Mary Messall writes about Physics in general:

The thing is stories don't give you numbers that can be checked by experiment. Equations do. Insofar as we demand that our science be experimentally verifiable, we're demanding that it consist of equations. In that sense there's no such thing as "a scientific explanation." Explanations are inherently unscientific -- unpredictive, unfalsifiable.

What's more, I find (to my dismay) that a great many, perhaps even the majority, of the equations we're given in class are used *without* interpretation. Sometimes I wander around demanding an interpretation for some specific expression from everyone in the department, and mostly I eventually come up with some story that satisfies me, but it's amazing how many of the people I ask in the meantime don't know and *don't care*.

And they're better at solving problems than I am.

I'm a little bit bitter about some of the professors who've had that attitude. "Interpretation is the same thing as popularization, as speculation. Frivolous. Unrigorous. Beneath us. Shut up and calculate." They're right, in a way. It can't predict anything.

I guess I still think stories (and applications, which are usually disdained by the same people) are the [horse], and the equations are the [cart]. But the equations-for-their-own-sakes people may be better scientists than I am. I'm not sure.

It's a big enough idea that it deserves a post of its own. I've written about something vaguely similar in the area of lecture prep-- twice, in fact: one, two-- so it should come as no surprise that I tend to think of stories as an integral part of physics.

Contrary to what Mary says, I've found that the very best physicists I know (and this includes a couple of Nobel laureates, if I may be permitted a JVP moment) are the ones who have the best grasp of the stories and interpretations. At least for the sort of physics that I do, it's essential to ground your understanding of the physics in terms of the real motions of real atoms that are the basis of everything. If you can understand what's going on in simple terms, and more importantly explain it that way to other people, that's a big step toward being able to push experiments in new directions, and explore new phenomena.

To some degree, this is an issue of sub-fields. I work in atomic, molecular, and optical physics, where the problems we study generally involve a smallish number of atoms doing comprehensible things. Other fields rely much more heavily on sophisticated mathematical tricks to make their problems tractable, which makes it harder to tell stories about what's going on. I took one class on Solid State, and after the first couple of weeks, I no longer had the foggiest idea what was going on in terms of actual electrons moving through solid materials-- it was all "reciprocal lattice vectors," which I still don't understand-- which made it a deeply unpleasant class all told.

On the other hand, though, I think the link between success in physics and a good grasp of stories could be extended to many of the best and brightest regardless of research topic. Einstein's real breakthrough with Special Relativity was a matter of storytelling-- people knew before Einstein that Lorentz transformations would solve the problems with Maxwell's Equations, but thought it was too weird. Einstein showed that not only was it the right solution, but it had to be that way, and he did it by providing stories to make it all make sense (again, see some earlier posts: one, two). Schroedinger's equation is in some sense a story that makes Heisenberg's matrix mechanics palatable (the theories are mathematically equivalent, but as I understand it, nobody could make heads or tails of Heisenberg's stuff). And when you get down to it, what are Feynman diagrams but little stories about what happens to an electron as it moves from point A to point B?

Yes, in some sense, the equations are the main thing. But when you look at the history of physics, you find again and again that the real giants of the field are the people who matched an interpretation to the equations, who came up with stories to explain it all. Any fool with a computer can manipulate equations, but it takes real genius to explain what's going on in a way that makes it make sense.

I don't have a good answer to "What's a photon?", but at least I can say this: If you feel that interpretations and stories are an important part of physics, you're in good company.

Posted at 10:15 PM | link | follow-ups | 31 comments

Wednesday, April 28, 2004

Quantum Conundrum

Kate directed me to a post by Kathryn Cramer regarding interpretations of quantum mechanics, which I've recently written about. Specifically, it describes an experiment by a fellow named Afshar at Harvard, which claims to be able to distinguish between interpretations, and comes down decisively in favor of the "transactional interpretation" promoted by Kathryn's father. It's also cited in a talk he gave at Boskone earlier this year (you can view his PowerPoint slides, or see Google's cached version, which omits the crucial images).

The experiment as described is fairly clever, and is basically a variation on the classic "which-way" experiment. Light is passed through two narrow slits, which should result in an interference pattern on the other side of the slits, with no light at all reaching certain areas. At a position where there should be a clear interference pattern, a grid of fine wires is placed in the beam, with the wires positioned at the minima of the interference pattern (so no light should hit them). A little bit past the position of the grid, a lens is put in that focuses the light passing through the slits down to two distinct spots.

The question is, how much light should be blocked by the wires? If you go with a pure wave description, you would say that no light at all should be blocked, because the wires are at interference minima. However, you only get an interference pattern in the first place by setting up a situation where you can't tell which slit the light passed through. The way this is set up, you can tell which slit the light went through (in fact, you only measure one of them). In that case, you ought to get just a classical probability distribution, and you should lose something like 6% of the light to the wires.

The claim is that the standard interpretations of quantum mechanics predict a 6% loss, while the "transactional interpretation," which is too complicated for me to follow right at the moment (it's been a long couple of weeks), predicts no losses. The experiment shows no loss of photons, therefore only the "transactional interpretation" survives. (Cramer writes grandly that "two of the major interpretations of quantum mechanics have been falsified and should be relegated to the waste basket of physics history." Full disclosure: this does not make me especially well disposed toward her comments, particularly when put together with a later comment that "I'm down on grandiose pronouncements from people who post anonymously." Signed grandiose remarks are not a major improvement in my book.)

Of course, here's where the problems come in. This seems like it ought to be Big News if it's true, but I can't find any mention of it in any reliable sources. It's not on the porn server: arXiv shows no papers by anyone named "Afshar." And Google turns up nothing but blogs, which aren't especially reliable. Now, you might say that this is just so new that it hasn't hit the servers, but Boskone was back in February (I didn't go to the talk in question, opting for Jim Macdonald's panel on the Knights Templar instead), and if it was PowerPoint ready back then, it should've appeared somewhere by now, as a preprint if nothing else. There doesn't even seem to be a web page for Afshar's research group, which is decidedly odd.

So I don't really know what to make of this. I don't see an obvious hole in the experiment as described, but details are pretty scarce, so it's hard to judge. The interpretation of it seems a little too pat-- working out exactly what you really expect in these kinds of experiments is notoriously difficult, and it wouldn't surprise me if there's a perfectly reasonable explanation of the experiment in the more standard interpretations. But, as I said, I'm awfully tired and details are scarce.

Anyway, I throw this out there for anyone who has more information than I do to comment on. (Well, really, for anyone at all to comment on. But hopefully, somebody with more information than I have...)

Anyone know this guy, or know of this experiment? Revolution in the making, giant load of crap, or something in between?

Posted at 9:26 PM | link | follow-ups | 44 comments

Tuesday, April 27, 2004

Slacker Update

Taking a break from the tedious political ranting, I've added three new books to the booklog. This leaves me only, um, five books behind. Still, it's progress...

The new additions:

Check 'em out.

Posted at 1:34 PM | link | follow-ups | 11 comments

Monday, April 26, 2004

What Would Jesus Do?

Thanks in large part to a long and contentious thread at Electrolite, I've been thinking a lot about religion and politics lately. Probably too much-- I'm starting to approach the level of continual unaccountable irritation that means I need to stop reading political blogs for a week or two. Before I do that, though, I'll post this.

One of the more sensible observations made in the comments to that post and a later post on the same topic is that it's a Bad Thing that a particularly noxious sub-species of conservative Christianity has come to dominate public perception of religion, at least when it comes to politics. It's become conventional wisdom that the only religious people in politics are conservative Republicans.

This is particularly upsetting when you realize that Jesus was really a Democrat at heart-- he shunned the rich to hang around with working stiffs and riff-raff; he was a big advocate of giving money to the poor; he even rode a donkey into Jerusalem. You don't get more Democratic than that. The New Testament is one big leftist tract, and yet the whole Bible has been appropriated for political purposes by the Republicans, most of whom are howling hypocrites.

Here, then, is a suggestion of a fantasy-world ad campaign to address the problem (as alluded to in a comment over at It'd never work in the real world (it's probably illegal, at least as presented here), but I'd love to see somebody try.

Open with a clip of a Republican politician saying something fulsomely religious. Bush's citation of Jesus as his favorite political philosopher would be a good one.

Follow with a text screen asking "What Would Jesus Do?" Maybe a voiceover, too, just to drive it home: "Good point, Mr. President. Let's ask ourselves, what would Jesus do?"

Follow with a clip demonstrating some particularly un-Christian policy-- something having to do with pandering to the ultra-rich, say.

Follow that with a relevant Bible verse. Say, selected bits of Matthew, Chapter 19. For best effect, you might get a movie actor to read Jesus's lines. (It might be better to flip the order of the Bible verse and the policy-- you could play around with it a bit.)

Close with text and voiceover: "What Would Jesus Do? He'd Vote for a Democrat."

There are infinite variations of this, of course. I'd particularly like to see one that opens with Roy Moore and his monumental ego, followed up with some more Matthew, this time, from Chapter 6. There's no end to the possibilities, particularly if you could put someone who actually knows Scripture on the project.

Like I said, it probably violates campaign finance laws six ways from Sunday, but it's fun to imagine. An even bigger problem would be that the sort of thoughtful, liberal Christians that you would need to make this work are generally too decent to exploit their religion for political gain in that way. Which is kind of what got us into this mess in the first place...

If anybody wants to give it a try, though (you could maybe start with a website--, or, or you're welcome to the idea.

Posted at 7:43 AM | link | follow-ups | 5 comments

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