Preposterous Universe

Wednesday, March 31, 2004
Spacetime and Black Holes

This quarter I don't get to moonlight in the humanities; I actually have to teach a physics course. But it's a fun one: Spacetime and Black Holes, an introduction to general relativity for undergraduates. GR is Einstein's theory of gravity; it can be summed up in the simple statement "Gravity is the curvature of spacetime." It plays a crucial role in understanding black holes and neutron stars, the big bang and the accelerating universe, gravitational waves, and every attempt to quantize gravity.

Teaching GR to undergraduates is still unusual; at many places it isn't even a core graduate course. (Of course, these days they're teaching undergraduates string theory.) For a long time GR was somewhat outside the main action of physics, since our experiments didn't probe into regimes where it was important. That's certainly changed in recent years. GR also has something of a reputation for being difficult, which is quite untrue; it's intrinsically very straightforward, but the relevant mathematics (tensor analysis, differential geometry) is just so different than that used in other areas of physics that it seems like a big investment to learn.

This quarter I'll be using Jim Hartle's new book, which is a fantastically useful text. He approaches the subject with a physics-first attitude that allows the student to get to the fun parts without spending months learning formalism. (If they want to do that, they should take the graduate course and buy my book.) We just state without demonstration what the spacetime around a star or black hole looks like, and then dive right in to understanding its features. I've never actually taught it this way before, so it's something of an experiment. The worry is that the students will fear that they're getting a watered-down version of the true story, which really isn't the case. By the end they'll get the whole shootin' match. If I would just quit blogging and write my lecture, anyway.

Tuesday, March 30, 2004
Missile defense plea

The Bush administration is zealous about so many nutty things it's hard to keep track. Missile defense ("Star Wars" and its ilk) is one of them I had almost forgotten about. Apparently they hope to spend over $10 billion per year to develop a defense that doesn't work against an enemy that doesn't really exist.

Physicists have long known that the missile-defense plans are mostly scams; they are wildly optimistic, overhyped, undertested, and usually misrepresented. It's just hard to shoot down a bullet with another bullet; and when the incoming bullet can use countermeasures, it's practically impossible. Now a group of generals and admirals is saying the same thing: this is a colossal waste of money, let's spend that money doing something useful like, say, protecting against terrorism. The military experts have an uphill battle; they don't appreciate that the administration finds the battle against terror kind of boring, and is easily distracted by shiny objects.

Monday, March 29, 2004

Tomorrow Brian Greene will be visiting Chicago as part of a book tour. Brian is an accomplished string theorist, but best known as the author of the popular book The Elegant Universe, which last year was made into a NOVA special by PBS. Brian's new book is The Fabric of the Cosmos, which I have bought but not yet had a chance to look at, although I'm sure it's quite good. (Full disclosure: I know Brian a little bit, and my name even appears [misspelled] in the acknowledgments section of his book.) One of the reasons his books sell so many copies is that he really puts a fantastic amount of work into explaining recondite physics ideas in a way anyone can understand.

The reaction of professional scientists to popularization is an interesting and disturbing one. You would think that scientists would be overjoyed when someone with talent and charisma takes the time to explain their work to a wider audience. It's at the very least good for the field, and one could argue that it's the entire point of research in areas like cosmology and fundamental physics that are far removed from any imagined technological application. The reason we are paid to think about string theory and dark energy is because people are generally curious about the deep questions from which they originate, and it only makes sense that we would make an effort to tell people what we've found.

I vividly remember an incident in a California bookstore soon after the Elegant Universe TV special, late last year. There was a big pile of copies of Brian's book, and the pile was noticed by a boy who couldn't have been more than ten years old. He exclaimed to his mother, standing nearby:
"Mom, mom, look, it's the Elegant Universe book! We've got to get this for Dad!"

"Sure. What is the book about, anyway?"

"It's about string theory! He'll love it!"
Any professional physicist should be thrilled to think that ten-year-olds are getting excited about science this way.

But two things get in the way: jealousy and dignity. The jealousy is obvious; researchers don't necessarily like it when they see their colleagues spend time in the spotlight. They could imagine themselves there, or wonder why their research isn't featured more prominently. I've heard extremely famous scientists complain about the NOVA series in ways that were couched in generalities, but amounted to whining about the lack of credit given to them (or their close friends). In academia, of course, attribution of credit for work that you've done is the coin of the realm, and scientists naively expect that the same standards should hold in popular media. So anyone who seems to be appearing in newspapers and TV more often than they should tends to rile up their colleagues, who can respond in remarkably petty ways.

The dignity issue is trickier. Effective pedagogy sometimes calls for dramatic flourishes, or for whiz-bang special effects, or for highlighting aspects of science that might not be most important to the scientists themselves. Stooping to such levels can elicit disdain from your colleagues, often quite explicitly. I remember a workshop on dealing with the media at a meeting of Packard Fellows, supposedly some of the best young scientists around. When asked what concerns they had, a large number said they wouldn't think of talking to journalists, for fear that their senior colleagues would think they weren't serious scientists. It's part of a self-destructive attitude that scientists are going to have to get over if they want to continue to ask for public money, not to mention fulfill their obligation to share their discoveries with the wider world.

I just noticed that the amazon.com page for The Fabric of Spacetime says that six different people recommended The Privileged Planet as additional reading. A brief glance reveals that this book is ridiculous intelligent-design propaganda. Obviously someone had the bright idea of using amazon.com recommendations as a way of leading the unwary away from evil secular physics and toward the light.

P.S.: This blog owes its title indirectly to the Elegant Universe. The idea was, only a string theorist could think that our universe was "elegant," and only because they never went out and actually looked at it. Get it?

Sunday, March 28, 2004
The Fog of War

I finally had a chance to see The Fog of War, the Errol Morris documentary about Robert McNamara, Secretary of Defense during the Kennedy and (much of the) Johnson administrations. It was a great film, the kind you could talk about endlessly. I'll try not to do that, but a few things are irresistible.

First, the obvious parallels with our current mess in Iraq. McNamara was Defense Secretary during the escalation of the Vietnam war, so the connections are inevitable (and have been commented to death already). One does wonder what Rumsfeld would make of the movie. The most unbelievable moment to me was the account of a 1995 meeting between McNamara and the former Vietnamese foreign minister, to discuss what lessons could be learned. The minister explained to McNamara that the conflict was a civil war, that they were historic enemies of the Chinese, and that the US could not have "won" because the Vietnamese were fighting against a colonial power and would never give up. Amazingly, McNamara claimed to be shocked by these revelations (in 1995!). Cluelessness about the culture we are interfering with must be one of the most common themes of US intervention. That's the one very obvious connection to the Iraq adventure, which in many ways is a very different story.

Second, although Vietnam dominated the movie, the opening bit about the Cuban Missile Crisis was the most gripping. Given the insanity on all sides, it's miraculous that the world escaped without a full-blown nuclear war. McNamara quotes Castro as saying that if the US had invaded, he would have launched all the nuclear weapons on the island, knowing full well that the consequence would have been complete annihilation of Cuba. He also quotes our very own Gen. Curtis LeMay, who thought we should quickly launch an all-out pre-emptive strike against the Soviet Union before they could catch up to our nuclear arsenal. As I said, miraculous.

Third, and perhaps the only point that hasn't already been beaten to death, the movie rehearsed a tired critique of the concept of "rationality." A common criticism of McNamara when he was Defense Secretary, which is trotted out essentially unmodified in the movie, is that he and his staff (the "best and the brightest") were super-intelligent and supremely rational, yet continued to get us into all sorts of trouble. Clearly, we conclude, this rationality stuff isn't all it's cracked up to be. Well, rubbish. Rationality is never to blame for bad decisions, any more than arithmetic is to blame when you can't pay your bills. Rationality can tell you how to achieve certain goals through certain actions. If the result turns out to be a mess, there are two possibilities: the goals weren't the right ones, or your rationality was simply faulty. McNamara calls Castro "rational," just before he relates the anecdote that Castro was willing to have Cuba be completely destroyed. Sorry, the mistake there is not an overzealous application of instrumental reason; it's just being stupid. Rationality doesn't tell you that preventing the fall of dominoes in Southeast Asia is worth any possible cost in human lives; your nonsensical value system is telling you that, and rationality simply allows you to implement this craziness efficiently.

I'm sure that, if the situation in the Middle East deteriorates (even further), pundits will point to Rumsfeld and his crew and accuse them of being too rational, not sensitive enough to human needs and foibles, as if those qualities were somehow in opposition. This history-repeating-itself thing grows tiresome awfully fast.

Friday, March 26, 2004
Give the people what they want

By popular demand, I am forced to reveal the recipe alluded to below for burnt caramel ice cream. I found this recipe on the web years ago, and had lost track of where it came from. But a quick googling led me to this page, which leads me to believe that the original source was a small book called Wild About Ice Cream by Sue Spitler. Which apparently costs $1.50, which is not as cheap as getting things for free on the web but is pretty good. Anyway:

(Yields: 1 Quart or 950 ml)

1 C (190 g) granulated sugar
1 C (240 ml) hot water
4 eggs
1/2 C (40g) powdered sugar
2 C (450 ml) heavy cream
1 tsp vanilla extract

Heat granulated sugar and 1/4 C (60 ml) of the water in a large skillet on medium high heat until the sugar melts and boils, stirring occasionally. (Water will essentially boil away.)

Boil until mixture is a dark brown; remove from heat. Gradually stir in remaining 3/4 C (180 ml) water.

Cool to room temperature and set aside.

Beat eggs in a medium bowl until thick and lemon colored; gradually beat in powdered sugar.

Stir in cream and vanilla; stir in the caramel mixture. Chill. Freeze in an ice cream machine according to manufacturers directions.

(Bonus tip from long experience: The secret to great home-made ice cream is to keep all the ingredients as cold as possible, at least just before you put them into the ice cream maker. That way the mixture will freeze quicker, preventing ice from crystallizing and giving you a smoother product. Not as rich as Toscannini's, but surpassing anything outside the Boston area.)

Thursday, March 25, 2004
Public service announcements

Okay, so let's say you're in Chicago. You're taking the El (the elevated train; in Chicago the weather is always perfect, so there's no reason to put public transportation underground as in climates that aren't as blessed as we are). You get off at some stop, and the question hits you: What blogs are nearby? You can get the answers from Paul Goyette's Chicago blog map, organized by El stop. There are 131 blogs as of this writing, although I'm sure there are many more to be dug up and linked to.

Now let's imagine instead that you're morbidly curious about the political-donation habits of important people (or unimportant ones). Just check out the fundrace.org neighbor search. For example, the President's dad has donated to his pride and joy, just as you would expect. Less obviously, someone by the name of Howard Dean has donated to Bush as well. Or maybe that makes perfect sense.

Bill Gates has donated to Bush, but leading string theorist Ed Witten has donated to Clark and Edwards, and he's smarter. Not at picking winners, obviously, but you know what I mean.

(Game inspired by Wonkette.)

Wednesday, March 24, 2004
Under God

The Supreme Court is hearing arguments about the Pledge of Allegiance. I think that the "under God" bit is an unconstitutional travesty, but honestly I don't care too much; there are more important battles to fight. But this did amuse me:
Newdow, 50, held his own under a barrage of fast-paced questions. Chief Justice William Rehnquist threatened to clear the courtroom if spectators applauded Newdow a second time.

Rehnquist had asked what the vote was when the U.S. Congress in 1954 added "under God" to the pledge. The law was an effort to distinguish America's religious values and heritage from those of communism, which is atheistic.

Newdow replied the vote was unanimous. Rehnquist said that did not sound divisive to him. "That's only because no atheist can get elected to public office," Newdow answered, triggering the applause, a rare event in the high court.
The applause must have been good to hear. I'm glad that someone takes this seriously enough to devote some real effort to demonstrating the obvious.

Update: Amanda Butler at Crescat Sententia was in the courtroom for the oral arguments, and gives a detailed account of the proceedings.

Mars, water, life

NASA reports that the Martian rover Opportunity is sitting on an ancient shoreline. The texture of ripples on the rocks indicates that they used to be under water; it must have been at least a couple of inches deep, in order to create the observed patterns. (Did you know that Opportunity has her own blog? Two of them, actually.)

Let's indulge ourselves in thinking just about the scientific implications, instead of the icky politics. We instantly jump to speculations about life on Mars; the evidence is thin, but the temptation is irresistible.

I am by no means an expert on exobiology in general or Mars in particular, but it's clear that sorting this out is going to be both complicated and fascinating. We don't know all that much about the origin of life, to be honest. The famous Miller-Urey experiment showed that amino acids could be spontaneously generated inside a test tube filled with methane, ammonia, hydrogen, and water, if it was continuously zapped with electrical shocks (to simulate lightning). Amino acids are the building blocks of proteins, so this is certainly a step in the right direction.

But these days scientists think that the atmosphere of Earth long ago didn't actually have the right compounds. Never fear, though; it seems as if the conditions for making amino acids happen naturally in outer space! Comets in particular seem to be thick with organic materials, and meteorites that have fallen to earth turn out to occasionally have actual amino acids in them. You might worry that the delicate organic materials would get destroyed when objects crashed into the Earth, but there's some experimental evidence that they actually survive intact. In other words, it's quite plausible that interplanetary chemistry played an important role in the first steps toward the development of life here on Earth.

I bring this up because 1) it's intrinsically amazing, and 2) it's going to make it very hard to sort out the life-on-Mars story. We might find all sorts of organic molecules on Mars, not because they developed there by themselves, but because they were brought by comets. We might even find evidence of Earth-like life, again not because it arose by itself, but because it was carried from Earth by our own spacecraft, or perhaps by rocks ejected from volcanoes.

None of this makes the effort to understand the status of life on Mars any less interesting; all of the possibilities are fascinating, for different reasons. But it will be a long time before we can say anything with confidence. Unless there is an entire civilization hiding underneath the Martian soil, waiting for the right moment to spring out and attack. Someone should make a movie about that.

Tuesday, March 23, 2004
The most opinionated zip code in America

I'm spending a few days in Cambridge, Mass, site of my old haunts from grad school and my first postdoc. One of the few places in the world where running into string theorists on the street (as I did today) is not too surprising.

And I enjoyed a treat I hadn't had in years: Toscannini's burnt caramel ice cream. I've always loved ice cream, but this is the flavor that made me a fanatic. After moving to California for my second postdoc, and making a desultory appraisal of the ice-cream situation, I was moved to buy my own ice-cream maker and churn out the burnt caramel myself. Some good comes out of every hardship.

Cambridge has an absolutely unique charm, although it's not for everybody. I love the brick sidewalks, the scattered cafes and bookstores, the predominant scholarly aesthetic. I've only bought one book so far, but there are a couple of days left.

Monday, March 22, 2004
Inflation II

In the last post we talked about inflationary cosmology, the density perturbations it predicts, and how these perturbations show up in the cosmic microwave background (not to mention in the large-scale structure of galaxies today).

If this story is true, properties of the universe during the inflationary era are reflected (albeit faintly) in properties of the perturbations. For example, the overall amount of perturbation A (which is one part in 100,000) is related to the energy density of the universe during inflation; unfortunately it's also related to another number, the "slow-roll parameter" ε (epsilon), which describes how the rate of inflation gradually slows with time. (Have to be a bit technical here, sorry.) Roughly, the energy scale EI of inflation (the number which, when raised to the fourth power, is the energy density during inflation) obeys
EI = A1/2 ε1/4 EP.
Here, EP is the Planck scale, the magical energy at which quantum gravity is supposed to become important: EP=1018 billion electron volts. (A billion electron volts is one GeV, "G" for "giga-". The rest energy in a single proton, via E=mc2, is about 1 GeV.) For comparison, the highest energy yet probed by particle accelerators here on Earth is about a trillion electron volts, smaller than the Planck scale by 10-15. Accessible experiments are not going to tell us anything directly about energies as high as the Planck scale; cosmology might be our best hope for learning something empirical about quantum gravity. For more details about inflation and perturbations you can look at a technical introduction to inflation by Andrew Liddle.

Let's plug in numbers. The perturbation amplitude A is 10-5. The slow-roll parameter ε is supposed to be small, perhaps 10-2; but we're taking the fourth root, so we'll end up with something of order unity. This means that the energy scale of inflation EI appears to be of order 1015-1016 billion electron volts. This is intriguing, since this scale is right where we expect to have grand unification -- the coming-together of the three major forces in the universe other than gravity (electromagnetism, the strong nuclear force, and the weak nuclear force).

Could this be a coincidence? Sure. We certainly haven't been very precise, to say the least. But an optimist would see hints of a consistent picture forming, in which the physics of grand unification is somehow behind the phenomenon of inflation. It's by no means a complete theory, but an encouraging tidbit that is worth pursuing. Theorists will look for specific models of inflation, while experimentalists will look for new ways to test its predictions. Unfortunately, there aren't that many predictions. One is that the overall geometry of space is very close to flat; this has been spectacularly confirmed by observations of the microwave background and elsewhere. Another is that the fluctuations in density should be accompanied by independent fluctuations of the gravitational field (gravitational waves), which leave a distinctive signature on the polarization of the microwave background. Looking for such a signal is a big goal of cosmologists right now.

Meanwhile, the fact that the energy scale of inflation seems to be tantalizingly close to the Planck scale leads people to wonder whether we can't see explicit effects of quantum gravity in the CMB. It's hard to give a definitive answer to this question, just because we don't really know what the explicit effects might be. They might, for example, cause the perturbations to deviate from perfectly uniform behavior on all scales, perhaps by imprinting a tiny oscillating variation. But right now there's little consensus about this quantum gravity/inflation connection; we have a ways to go before making it into something concrete.

Sunday, March 21, 2004
Inflation and the microwave background

Peter Woit has some questions for cosmologists. Too many good ones to answer in a brief comment, or even a single post, but let's tackle the first big one, which is fun to talk about in its own right.

The general question is "What can observations of the cosmic microwave background tell us about physics at very high energies?" Since there's no reason why non-experts shouldn't follow the discussion, I should explain briefly what the microwave background is and why "high energies" are interesting. It will take some time, but it's not useless for me, since I'm supposed to be writing some public-education web pages for the Kavli Institute for Cosmological Physics (formerly "Center for Cosmological Physics") here at Chicago, and I'll use this as a rough draft.

The cosmic microwave background (CMB) is the leftover radiation from the Big Bang. When the universe was much smaller it was much hotter, emitting blackbody radiation just like anything else, and we can detect that radiation today. The very early universe was so hot that it was opaque, since the electrons were ripped off of individual atoms and photons kept bumping into them. At 370,000 years after the Big Bang, the temperature had dipped below about 3,500 Kelvin, cool enough for electrons to recombine with nuclei to make atoms, and the universe suddenly became transparent. The radiation subsequently cooled to about 2.7 Kelvin, which is what we see today; it provides a snapshot of what the universe looked like when it was 370,000 years old (it's 13.7 billion years old right now, or about 100 billion dog years).

What it looked like was something extremely smooth; fluctuations in density from place to place were only about one part in 100,000. But we can detect these fluctuations; the image reproduced here is the famous map from the Wilkinson Microwave Anisotropy Probe satellite. Blue regions are slightly colder than average, red regions are slightly hotter. (The WMAP team actually knows physics much better than this color scheme would lead you to believe.)

There is a treasure trove of information contained in these fluctuations. In particular, statistical properties of the fluctuations depend on two things: the primordial perturbations from which they presumably arose, and the recipe of ingredients in our universe that controls the subsequent evolution of the perturbations between early times and now. Remarkably, an extremely simple specification of primordial perturbations works very well -- simply imagining that the perturbations are (on average) of equal strength at all distance scales. From this guess, and the observed fluctuations in the CMB sky, we can derive very tight constraints on interesting cosmological parameters, such as the amount of ordinary matter and dark matter in the universe. See Wayne Hu's tutorial for details.

But the simple guess for the form of the primordial perturbations is actually better than a guess -- it's a prediction of the inflationary universe scenario. Inflation is the idea that the extremely early universe underwent a period of accelerated expansion that stretched a tiny portion of space to the size of our entire observable universe. It was originally invented by Alan Guth and others to help explain precisely why the universe looks so smooth on large scales. See this intro by Ned Wright for more details.

Inflation came with an unexpected bonus. Try as it might, inflation can't make the universe perfectly smooth, simply due to the strictures of quantum mechanics. Heisenberg's uncertainty principle tells us that we can't specify the state of a system with perfect precision; there is always an irreducible jiggliness when we look at, for example, the position of an electron. But the principle holds as true for the entire universe as it does for an electron. So inflation makes the universe as smooth as it can (imagine removing the wrinkles form a sheet by stretching it at the edges), but there is some amount of fluctuation left over -- which, of course, precisely describes the universe we see. All of the stars, galaxies, and large-scale structure in our universe may have started as tiny quantum fluctuations in the primordial soup.

Okay, this has gone on a while already. Next time I'll be more quantitative about the perturbations, and talk about how they might reveal something about physics at very high energies.

Friday, March 19, 2004
Just some links

From Tbogg, a link to an article at Axis of Logic on the status of 9/11 as a political football, and in particular who is to "blame" for the incredible intelligence failure. This is a topic where it's hard to find level-headed discussion, but this article is sufficiently well-documented as to be quite persuasive. Not to give you the wrong impression -- it's completely partisan, but defensibly so.

Astronauts who have risked their lives to explore space are joining the chorus to save Hubble. Let's keep it up, hopeless though it may seem at the moment.

Peter Woit has a new blog. He's a mathematician who argues that string theory (our attempt to derive a consistent quantum theory of gravity from a theory of extended objects, rather than ordinary point particles) is bad news for physics. I don't agree, but it's worth listening. I think string theory is fantastically promising and quite remarkable, but plenty of scientists (including particle physicists and gravitational physicists) disagree, which is an interesting state of affairs. Some time in the future our current generation of string theorists will either be viewed as visionary pioneers soldiering forward despite overwhelming odds, or misguided crazies who derailed progress in physics with their hopeless detachment from experiment. Maybe we'll live to see which one.

Thursday, March 18, 2004
The cost of w

Out here in the desert today we were worrying about dark energy. Seventy percent of the energy in the universe is some mysterious stuff whose density, as far as we can tell, remains constant as the universe expands. (In contrast to, say, ordinary matter, which dilutes away as a result of the expansion.)

The leading candidate for dark energy is vacuum energy, or the cosmological constant, which is exactly constant throughout space and time. But it's not an especially attractive candidate, so we're looking for alternatives anywhere we can -- some persistent but nevertheless dynamical field, or even a modification of gravity on large scales.

To tell if the dark energy is vacuum energy, we try to see whether it's changing or absolutely constant. The parameter we go out and measure is w; its value is -1 for pure vacuum energy. We know that w is pretty close to -1; if it's a little bit greater (like -0.9) the dark energy is gradually diminishing, while if it's less than -1 the density is actually increasing. (The amount of dark energy per cubic centimeter is going up everywhere in the universe.) That seems crazy, which was what my talk this morning was about. It is crazy, but it can't be completely ruled out, so we should keep an open mind.

The first direct evidence for dark energy came from using supernovae as standard candles (objects whose intrinsic brightness is known, so their distance can be inferred from their aparent brightness). Many of the talks today were devoted to current and future supernova searches. There was much discussion between the observers, who wanted to know just what kind of deviation from w=-1 we should expect, and theorists (like myself) who kept admitting that we have no idea. I don't think they believed us. Unfortunately it's a question we have to keep asking, since it costs money to do these observations; money is tight, and we have to decide which experiments are most deserving of our efforts.

Wednesday, March 17, 2004
What is w allowed to be?

The enigmatic title isn't anything I can explain right now; it is the title of the talk I'm supposed to give at the conference in Tuscon at which I just arrived. A collection of cosmologists at a golf resort in the desert; who thinks of these things? The talk is tomorrow morning, and it's not written yet, so no substantive posting today.

Instead, read Michael Bérubé's ideas about conferences. Spit-takes and electric shocks are involved, so you won't be wasting your time.

Tuesday, March 16, 2004

Tomorrow (Weds) I'll be a guest on Odyssey, a syndicated program from WBEZ, Chicago's public radio station. We're supposed to be talking about the "early universe"; of course, what's early to one person may be pretty late to another. I think we'll be covering a lot of ground, from 10^(-35) seconds (inflation) through one minute (nucleosynthesis) and 400,000 years (the cosmic microwave background) up to 500 million years (the earliest galaxies). The other guest will be Bob Kirshner from Harvard, a supernova expert and one of the co-discoverers of dark energy. Bob is an engaging speaker and a great scientist; I reviewed his popular-level book for Nature, and we managed to remain friends.

If your local public radio station doesn't get Odyssey, you can easily listen on the web. (I've been on a few times before, the shows are available in the archive.) But even better, you should call your local station and demand they get the program. It's an hour-long discussion, typically with two or three guests, about every sort of topic you can think of, with a decided emphasis on high-level (but accessible) intelligent discourse. The host, the glamorous and charming Gretchen Helfrich, does an amazing job of keeping the dialogue lucid and amusing no matter what the topic is.

[Update: here's the audio. The metaphor of the moment was that of a movie in which the first reel is mostly missing except for a few frames. Personally, given that our universe is pretty clever, but prone to violence and self-indulgence, I'm thinking it's a Tarantino film.]

Monday, March 15, 2004

Grading papers right now for our Moments in Atheism class. I figured that I would learn a lot from reading these (at least the good ones), and it's true. One of the students (Nicholas Boterf) found a wonderful quote in Juliette, a 1797 novel by the Marquis de Sade. Juliette is somewhat scandalized by the implications of what her "tutor," Madame Delbene, has been telling her:
"But ... if there be neither God nor religion, what is it runs the universe?"

"My dear," Madame Delbene replied, "the universe runs itself, and the eternal laws inherent in Nature suffice, without any first cause or prime mover, to produce all that is and all that we know."
I tend not to go along with some of the Marquis' ethical deductions from the godlessness of the world, but he got it exactly right with that quote.

For me, one of the rewards from looking at the history of these ideas was a better understanding of the change in perspective between Aristotelian mechanics and Galileo/Newton. Only now does it make sense why anyone would think the "first cause" arguments (Aristotle, Aquinas, etc.) held any weight at all. Aristotle thought that, to keep an object moving in a straight line, you had to keep pushing it. This seems silly to us post-Newtonians, but in fact it's pretty straightforward. Take a chair sitting on the floor and give it a push -- once you stop pushing, it will stop moving. "Aha," you say, "but that's only because of friction. If we ignore the friction, objects continue to move in straight lines unless forces act upon them." True, but highly non-intuitive. Why should we ignore friction, when it is ubiquitous in the real world abound us? Aristotle wasn't making a mistake, he was accurately describing the world he saw. If we take his description seriously, it's not so crazy to argue all the way to God. Lots of things in the world are moving, and moving objects require something to keep them moving, and ultimately that thing will be God.

Galileo's insight -- that the way to describe dynamics is to ignore friction and air resistance, find a simple model for the resulting motions, and then re-introduce friction afterwards -- was one of the most important moments in the history of science, and indirectly of religion as well. After he and Newton figured out conservation of momentum and the laws of motion, the Aristotle/Aquinas line of argument suddenly makes no sense. We don't need a "cause" or "mover" to explain why things are moving; that's the natural thing for them to do. This Newtonian revolution was, at a purely intellectual level, just as important as the Darwinian revolution for taking the philosophical wind out of religion's sails. After Newton, the primary justification for God shifted from cosmological arguments about first causes, to design arguments. Then Darwin made those seem silly (although Hume had done a pretty convincing job years before).


Have we discovered a new planet in the outer regions of the solar system? NASA seems to think so. Two orbiting telescopes -- the Hubble Space Telescope, about which we've been ranting previously, and the Spitzer Space Telescope, a relatively new infrared observatory named after my Ph.D. advisor's Ph.D. advisor -- have both seen evidence for a relatively large new object. It might be as big as Pluto. Deciding that the Roman pantheon has become politically incorrect, the new object has been named "Sedna," after the Inuit goddess of the ocean.

This is fun, but not an earth-shaking (as it were) discovery, to be honest. There's likely to be all sorts of medium-sized rocky objects lurking in the far-flung regions of the Sun's orbit. And the debate about whether Pluto is really a planet was boring and silly. Probably there is an advanced civilization floating deep in the atmosphere of Jupiter, that spends coffee breaks arguing whether Mercury, Venus, Earth and Mars should be classified as planets. (Okay, not "probably.") But the relentless series of new discoveries has to make the Hubble-killers uncomfortable.

Sunday, March 14, 2004
Hubble's fate

NASA Administrator Sean O'Keefe's decision to cancel future servicing missions to the Hubble Space Telescope has been met with an outcry from scientists, politicians, and ordinary people all over the world. It's been very difficult to figure out what O'Keefe's response really is. On the one hand, he has agreed to request a new National Academy of Sciences report that would study the pros and cons of future servicing missions. On the other, he continues to say (for example in today's New York Times) that he won't authorize a new Shuttle mission that is inconsistent with the guidelines set forth by the Columbia Accident Investigation Board -- which an HST servicing mission would be, since there is currently no way for a Shuttle crew visiting HST to inspect the orbiter for damage.

Safety is the most common argument against future servicing missions -- fortunately for those of us who favor new missions, it's a completely ridiculous argument. True, manned missions to space are dangerous, no matter what precautions we take. But does anyone in their right mind think that a visit to HST is more dangerous than a trip to Mars? The astronauts who comprise shuttle crews understand the risks, and would be more than eager to get the chance to upgrade Hubble. The only real argument is about money.

Which is completely ludicrous, since the budget includes a hefty chunk of change for future missions and upgrades to the International Space Station. The ISS has been a sad boondoggle from start to finish, a laughingstock in the scientific community. A combination of international obligations and a politically-astute dispersion of ISS contracts throughout multiple congressional districts make this beast impossible to kill. Apparently the Administration's plan is to spend a huge amount of money finish building it (just barely), and then declare victory ("Mission Accomplished"?) and let it rot up in orbit.

Meanwhile, clever folks at NASA are examining all sorts of imaginative proposals for servicing Hubble robotically, without a manned mission. These guys are good, and it may be possible to keep the observatory orbiting and operating for longer than its current expected lifespan of 3-4 years. But it's nearly impossible to imagine upgrading the telescope with the new instruments that have already been built. Regardless of this effort, it's absolutely worthwhile to keep pushing for another servicing mission to HST.

(I suppose posts like this don't help my chances for future NASA funding very much.)

Related: Ultra Deep Field.

Saturday, March 13, 2004
Collecting is such a nice hobby

Donald Rumsfeld was apparently very fastidious when he first toured the Pentagon after 9/11; enough that he walked away with a piece of the crashed airplane as a souvenir. (Original link from Fark.com.) He keeps it on his desk, and shows it to visitors as a reminder of the tragedy. Which, I guess, might otherwise just slip his mind completely.

Friday, March 12, 2004

That last post I put up was in a hurry (catching a plane back to Chicago), and it didn't quite form the crystalline structure of unassailable logic that, you know, all the other posts do. So let me elaborate a little. (I could just go back and edit the thing, nobody would know; the technology lets me, but it seems like cheating. I bet Robert Novak wishes he could do that.)

First, why the ad is bad: not because it suggests that the terrorists responsible for the 9/11 attacks were Arabs, but because it appeals to irrational fears rather than making a reasonable argument for certain policy choices. (Probably "xenophobic" would have been a better adjective to use than "racist" in the original post.) It's an emotional cheap shot; those are trite but unobjectionable when they are sugary and uplifting ("Morning in America"), but odious and inexcusable when they appeal to our less-lofty sides.

Second, is it a good campaign strategy? I really don't know. But it does seem to be a little early to be stooping that low. As I understand the conventional wisdom, a negative attack (such as this obviously is) may initially be effective, but over time can lead to backlash. So in the last few weeks of a campaign, they can be quite useful, but at this early stage Bush is going to take so much grief from the ad that it hardly seems worth whatever benefit he might get. Another good question I don't know the answer to: of the people an ad like this might hope to influence (swing voters who actually haven't made up their minds, and mildly-apathetic folks who need to be prodded to vote), how many will see the ad but not hear the accompanying media commentary, and how many will get the commentary without the ad? I'm sure the pros have calibrated this backwards and forwards. (Right?)

Bush ads

Ever since Homicide went off the air, my TV viewing is largely limited to NBA games, Queer Eye, and occasionally the Iron Chef. So I don't get to see a lot of the new campaign ads. Blogosphere to the rescue, however, as we can easily dissect every new ad without ever reaching for the TV remote.

The latest Bush ad takes a step that nobody should find surprising, but some find upsetting: using an image of an olive-skinned, vaguely Arabic-looking man to symbolize the threat of terrorism. (The ad is discussed, with screenshots, by Ryan Lizza at TNR and Billmon at Whiskey Bar.)

Bush supporters can say (and already are saying, e.g. at Little Green Footballs) that this is no big deal -- after all, the Sept. 11 terrorists were olive-skinned Arabs. This is a true statement, just as it is true to say that the DC snipers were African-American, or that Timothy McVeigh, the Unabomber, and Jack the Ripper were all Caucasian. Under the hypothesis that all statements of fact are equally appropriate, I suppose there's nothing more to say. But this is a blatantly racist appeal: Bush will protect us from the scary Arabs. Not only is it repulsive, it's also not a sensible long-term strategy for fighting terrorism (which comes in all colors, as folks in Ulster will tell you). But who knows, maybe it will work as a campaign theme.

Atrios points to this post from Poor Man, reconstructing the ad the Bush campaign would really like to have made, if the liberal media would let them get away with it.

Thursday, March 11, 2004
Why do we remember the past?

I'm visiting the Perimeter Institute, a swanky Canadian center for theoretical physics. They're open to speculative ideas here, so I gave a talk yesterday about the arrow of time.

The celebrated Second Law of Thermodynamics tells us that entropy, a measure of the disorder in a system, tends to increase with time (unless some outside influence acts to increase the order). The first person to understand this phenomenon was Ludwig Boltzmann (who later committed suicide). Boltzmann realized that the entropy was a measure of how many ways a system could be arranged that were basically indistinguishable. For example, if we have some gas distributed uniformly throughout a box, we can move individual atoms around in many different ways without affecting basic features like the density and pressure; so a uniform gas has a high entropy. But if all the gas is squeezed into one corner, there are fewer rearrangements that leave the system basically unchanged, so the entropy is lower. We therefore expect that gas can easily spread from a single corner to fill the box, but it's very unlikely that uniform gas will suddenly congregate in one tiny region. Thank goodness, or breathing would be a constant adventure.

But Boltzmann also realized the major unsolved problem: entropy only increases because it was very low in the past. Why did the universe start out that way? We still don't really know the answer. In my talk I proposed an answer, that I've been working out with Jennifer Chen. We make the very simple suggestion that the entropy is increasing because it can always increase -- in the real universe, there is simply no state of maximum entropy. So the fact that the entropy is going up is very natural, since it can always do that. The crucial ingredient we use is the idea of eternal inflation. "Inflation" is the idea that a tiny region of space can expand at a super-accelerated rate, growing into a size much larger than our entire observable universe. Eventually this process ends in most places, and the inflating universe converts into a more conventional Big-Bang cosmology; but "eternal" implies that it never ends everywhere, there's always some region far outside what we can observe where inflation is still going on. This process of inflation both constantly generates more and more entropy, and creates large regions that look just like our observed universe in the process.

The title of the post refers to the fact that memory relies crucially on the second law of thermodynamics. Why do we remember the past and not the future? Because, as entropy increases, we develop correlations between the external universe and our brains; if our universe was in a state of maximum entropy (thermodynamic equilibrium), we wouldn't be able to remember the past or the future. (We wouldn't really exist as complex organisms, for that matter; thank the universe for small favors.)

Wednesday, March 10, 2004
Ultra Deep Field

The Hubble Space Telescope, in a spiteful attempt to make NASA look silly for canceling future servicing missions, continues to crank out wonderful new results.

This is a detail from the new Ultra Deep Field. They point the telescope at one small region of the sky and just let it sit there, gradually collecting the tiny number of photons that are coming to us from these galaxies in the early universe. The objects seen here formed approximately 500 million years after the Big Bang; in a 14 billion year old universe, that's pretty young. Besides being a pretty picture, images like this help astrophysicists to figure out the processes by which galaxies became assembled out of the nearly-uniform plasma of the earliest times.

Tuesday, March 09, 2004
One more thing

Looks like both Kerry and the media are going after Bush for only spending an hour with the Sept. 11 commission. Here's Kerry, from Eschaton:
Kerry, who has accused Bush of impeding a federal commission investigating the terrorist attacks of Sept. 11, 2001, said Monday while campaigning in Florida, ``If the president of the United States can find time to go to a rodeo, he can spend more than one hour before the commission."
And here's an excerpt from the White House press briefing, from Talking Points Memo:
Q: You just said, “all the questions they want to raise.” That means he’s no longer going to limit it to an hour?

McCLELLAN: Well, that’s what it’s scheduled for now. But, look, he’s going to answer all the questions they want to raise. Keep in mind that the commission --

Q: If they’re still asking at one hour, he’ll still answer them?

McCLELLAN: Keep in mind that the commission has already had access to all the information they requested, as I just pointed out, including our most sensitive national security documents. That’s what I’m talking about when I’m talking about unprecedented cooperation. And the commission has also -- yes, let me finish --


Election day in Illinois is a week from now, March 16th. As usual we are too late to have any impact on the Presidential nomination process, but there's an important Senate race. Republican Peter Fitzgerald is retiring, and chances are good that he'll be replaced by a Democrat.

I'll be voting for Barak Obama. (He seems to be leading the race at the moment, but my preferences are usually the kiss of death, so he'll likely be issuing a press release declining my endorsement.) Not only was he president of the Harvard Law Review, he also has the grooviest campaign song of any of the candidates. (Via Crescat Sententia.)

I'll be traveling for the next week -- first the Perimeter Institute, then the University of North Carolina -- so blogging may be spotty. Hang in there.

Monday, March 08, 2004
The Big Rip

I promised earlier that I would talk about the Big Rip, but never got around to it, so here you go.

Since Edwin Hubble discovered in 1929 that the universe is expanding, cosmologists have suggested two possible ultimate fates for our currently-expanding universe: it could cease expanding and recollapse, eventually reaching zero size in a Big Crunch, or it could expand forever, but gradually more slowly (the Big Fizzle?). In a universe dominated by ordinary matter and radiation, these were really the only choices. Now we know that most of energy in the universe is some persistent dark energy that doesn't diminish as the universe expands, and can continue to feed the expansion rate; therefore another possibility becomes likely, that the expansion will continue at a constant rate forever. Confusingly, a universe with constant expansion rate is said to be "accelerating," because any individual galaxy appears to be accelerating away from us. That's because Hubble's Law says the recession velocity is the expansion rate times the distance (v = Hd), so a constant expansion rate H implies an increasing velocity v.

But there's a lot we don't know about dark energy, so it's prudent to keep an open mind. The simplest dark energy model is an absolutely constant "vacuum energy," but we can consider dynamical models in which the energy density is slowly decaying. Robert Caldwell and others have even suggested that the dark energy density (the amount of energy per cubic centimeter) might be increasing with time, a possibility he dubs phantom energy.

This opens the possibility of a Big Rip, in which the expansion rate increases without bound until it reaches infinity at some finite time in the future. This scenario was explored by Caldwell, Kamionkowski, and Weinberg. The consequences are dramatic: first galaxies, then stars and planets, then atoms and nuclei are ripped apart by the expansion of the underlying spacetime. The recent supernova results that were in the news indicate that the dark energy density is changing very slowly, if at all, so the Big Rip would have to be some time in the distant future (if, once again, at all).

It's important to realize that the quoted numbers depend on an enormous extrapolation, one we have little reason to trust. Phantom energy density increases as the universe expands; but the above analyses made the simplifying assumption that the increase proceeded at a constant rate. In other words, imagine hopping in your car and accelerating to the speed limit, but then estimating your arrival time by guessing that your acceleration (rather than your speed) remains constant. You'd be able to get across the country awfully quickly if that were true; but it's not a safe assumption.

The truth is, we can't predict the future of the universe with any reliability at all until we understand much more about the underlying physics of the dark energy. If it is increasing, it might only do so temporarily, before leveling off to a constant value (see my paper with Hoffman and Trodden). If it's currently a constant, it may decay completely away in the future. So, the choice between Crunch, Fizzle, and Rip is one we have no way to decide between right now. (But "Crunch, Fizzle, and Rip" is a great name for a band, or maybe a law firm.)

Saturday, March 06, 2004
Career choices explained

Here is why I could never be a politician. (Not that there are any movements afoot to draft me for major public office.)

A few weeks ago some friends and I went to the Lesbian Community Cancer Center Project Annual Ball (or the "Lesbian Prom" for short). True, I lack the traditional prerequisites for being a lesbian (female, homosexual), but it was a tolerant atmosphere, and my eccentricities didn't seem to bother anyone.

The whole event was great fun. About a thousand people attended, festive, well-dressed (not as many outrageous costumes as Jerry Falwell would expect, but enough to be entertaining), and generally enjoying themselves in an easygoing and friendly atmosphere. It was a party, not a political event, and activism was in the background for the evening. It wasn't until brief remarks associated with the presentation of some awards that anyone mentioned the same-sex marriage controversy. It only then struck me (I know, I'm slow) that all of these people around me, cheerfully having a good time, are systematically classified as second-class citizens in our country.

I doubt that anyone could get elected President today if they came out and said "This issue is completely ridiculous, of course same-sex couples should be allowed to marry." But I wouldn't be able to say anything else. We all know that progress in real-world politics sometimes relies on strategic compromise, and an ability to carefully prioritize efforts on controversial issues is absolutely necessary. But this one is simply not a close call. Furthermore, I don't even think it's especially interesting to talk about the arguments pro- and con-. It would be like debating whether apartheid was good or bad. (Racial discrimination is different than discrimination against gays, and drawing analogies between them isn't generally useful, but one is just as obviously wrong as the other.)

To be fair, we're not talking about what people should be allowed to do in the privacy of their bedrooms, but about whether society should extend a certain legal status to couples for whom the status was not originally intended. "Marriage" is an invented institution, originally intended to apply to male/female couples. There are undoubtedly all sorts of interesting historical/anthropological/sociological questions to be investigated about how the concept of marriage arose and what purposes it served in early societies. So what? In our actual world, marriage serves as a legal imprimatur to a romantic bond between two people in love. Some married couples have children, some don't; some marriages last a long time, some don't; some marriages are equal partnerships between two people, some are not. There is absolutely nothing about the contemporary idea of marriage which doesn't make just as much sense when applied to same-sex couples as applied to opposite-sex couples. Convoluted rhetoric aside, the only possible ground of opposition to same-sex marriage is a conviction that homosexuality is wrong -- a conviction which I don't think deserves any respect.

Here is one example of an attempt at reasonable discussion of the issue, from Eugene Volokh:
[T]here's an eminently legitimate argument that society would be better off if male-female couples were set up as the preferred, most legally and socially sanctioned mode. It is plausible to think that future generations would be better raised by male-female couples than by same-sex couples. And it is plausible to think that on the margins the laws related to marriage may subtly shift some people, either through incentive effects or through the law's effects on social norms, towards male-female coupling and childrearing.

Now as it happens I'm not persuaded that these arguments are actually correct. I suspect that a same-sex couple that has gone through substantial effort to have a child will probably be at least as good parents as the average male-female couple, which might have had the child with much less forethought, work, and desire for a child.
I found this excerpt on Alas, a blog, who pointed out:
The problem with this analysis, as I see it, is that it fails to acknowledge that men and women are individuals, and should be given the opportunity to live their lives as individuals, not just as representatives of their sex.
Well, yeah. Do we really need this pointed out? I actually find it completely implausible that children raised by same-sex couples would necessarily (or even usually) be worse off than those raised by male-female couples. Does anyone in the world really believe that, given information about the psychological and socio-economic status of some selection of individuals chosen randomly off the street, they would be able to accurately judge which ones had been raised by single parents, which by divorced and remarried parents, which by same-sex parents, and which by traditional nuclear families? The argument might be logically coherent, but I can't agree that it's plausible. It would actually be more plausible to claim that children are better off if they are raised by wealthy parents than by poor ones; should we have minimum income requirements for prospective couples? Somehow I believe that the rights of the individual parents should be more important than some ham-handed social engineering.

Volokh continues:
But the arguments against same-sex marriage mentioned above are not ridiculous arguments, nor arguments that can only be justified by irrational hostility or contempt. These are arguments that sensibly cautious and methodologically conservative people can reasonably make against proposed changes in a fundamental social institution.
That's precisely where I can't agree. And I am convinced that, a few decades down the road, anyone who today is against same-sex marriages will be judged just as badly as everyone else throughout history who has fought to preserve discrimination of some minority on the basis of an irrational aversion on the part of the majority. (I don't mean to single out Volokh, who is simply explicating the least-unreasonable arguments for the wrong side.)

Discussion of various aspects of the same-sex marriage controversy can be found at Andrew Sullivan, Angela Vierling, Dispatches from the Culture Wars, and Galois. There's certainly a lot to say, from articulating defenses of basic rights to strategizing about the best balance between principle and politics. But I don't personally have the patience to participate.

So that's why I could never be a politician; on issues like this I find it impossible to be diplomatic. It's possible to have reasonable disagreements about all sorts of things, from free trade to education reform to fiscal policy to foreign-policy strategies. I just don't see how it's possible to have reasonable disagreements about this one.

Besides, the idea of spending the winter months in Iowa, trudging between town meetings to declare my support for ethanol subsidies? No, thank you.

Friday, March 05, 2004
Peppermint Dark Energy

As advertised, I was on Science Friday this afternoon with Adam Riess and Richard Ellis. (Listen here; registration required.)

We talked mostly about dark energy, the mysterious stuff that is smoothly distributed through space, constant (or nearly so) as a function of time, and makes up 70% of the energy in the universe. It's mysterious for several reasons. For one thing, the leading candidate for dark energy is vacuum energy, which is just a kind of energy that is perfectly constant throughout space and time; but our estimates of how big the vacuum energy should be are larger than the observed amount of dark energy by one hundred and twenty orders of magnitude (a one followed by 120 zeros). For another, the amount of dark energy is comparable to the amount of matter in the universe (the other 30%), even though they change dramatically with respect to each other as the universe expands.

An issue that arose during the discussion was whether dark energy worked against gravity. It's important to understand that dark energy is not a new "force," but a new kind of "stuff," that creates its own gravitational field. The funny thing is that this gravitational field pushes things apart, rather than pulling them together. But the force communicating the push is just gravity as Einstein figured it out -- a manifestation of the curvature of spacetime.

We also talked about crazy new ideas, which are certainly worth considering. (It was during the course of this discussion that I extemporaneously introduced the concept of "peppermint-flavored dark energy," although I'm not sure that will catch on.) Crazy ideas range from some energy source that changes slowly, but is nevertheless dynamical, all the way to tossing out Einstein's general relativity and invoking new behaviors for gravity. People have tried all sorts of things, and should definitely keep trying, but so far the vanilla-flavored dark energy remains the model to beat.

Free advice

It's good that the press isn't letting Bush just get away with using images of the World Trade Center in campaign ads. Kerry cannot let Bush be the presumptive anti-terror candidate. Next time Kerry gets asked about those ads in an interview or debate, he should say something like this:

I think it reveals something about the President and his campaign. Personally, I don't think it's appropriate to use images of Ground Zero for political gain. Of course we should have a debate about how best to combat terror and preserve our national security, but our memories of the September 11th tragedies should be treated with respect. This president won't spare more than one hour of his time to talk with the commission investigating what went wrong on 9/11; to me, that says he's just not willing to do what it takes to make sure a tragedy like this never happens again.

I'm sure the Kerry campaign is overjoyed to get such insightful advice for free over the web. Here at Preposterous, we toil selflessly for the greater good.

Thursday, March 04, 2004
How many points for a three-pointer?

Maybe my final exams are too hard, after all. At the University of Georgia, former assistant coach Jim Harrick Jr. (son of head coach Jim Harrick Sr.) taught a course in 2001 on Coaching Principles and Strategies of Basketball. There was only one exam, including questions along the lines of "How many halves are in a college basketball game?" and "In your opinion, who is the best Division I assistant coach in the country?" (Correct answer: C, Jim Harrick Jr.)

The test in its entirety is here. Everyone in the class got an A. Both coaches recently lost their jobs following an NCAA investigation of multiple rule violations.

Wednesday, March 03, 2004

I'm spending all day Thursday at DePauw University, as a guest of their Science Research Fellows program. It should be fun, although they're keeping me busy: a lunchtime talk, two seminar class discussions, and a public lecture in the evening. The lunchtime talk will be a reprisal of one I gave at a conference on "God and Physical Cosmology" last year at Notre Dame. The conference consisted primarily of theologians and philosophers, but they invited a couple of cosmologists (Joel Primack and me) along to give some scientific perspective. I didn't really want to give a standard gee-whiz cosmology talk, so they let me talk about Why (Almost All) Cosmologists are Atheists. As you can read, it's just the standard argument about why scientific reasoning leads to a firm rejection of a supernatural being as an explanation for what we see in nature; the kind of thing you'll find in Richard Dawkins or Steven Weinberg.

I went into the conference having no idea what the response would be; this was, after all, the only conference I had ever been to where there was a prayer to open the banquet. But as it turned out they loved my talk. I didn't change anybody's mind, nor did I expect to (although one participant did say that I had convinced him once and for all that the argument from design wasn't one that theists should rely on). But they were very happy to get a completely different perspective, and I think they were pleased to really hear what a cold-blooded scientific materialist actually thinks, rather than just being humored. I certainly give everyone at the conference credit for being good sports (which academic theologians generally are, in my experience).

Meanwhile, on the drive down from Chicago, I found an evangelical radio program explaining in quite a bit of detail why "old-earth" theories of evolution had been convincingly disproved, and correct scientific analysis had demonstrated that most geological features originated in an hydraulic catastrophe (the Flood) four thousand years ago. (Ed Brayton has an interesting discussion of just this issue.) So the discussion continues, needless to say, on multiple levels.

Science Friday

Here is synergy for you. This Friday I'll be a guest on NPR's Science Friday, in the second hour (3:00-4:00 Eastern time). One of the things we'll be talking about is dark energy, including some new data bearing on whether the universe will be torn apart in a Big Rip. (The Big Rip is a little overhyped, actually; hopefully I'll say more about that later.)

But one of the reasons I was invited was that the producer, Annette Heist, noticed that I had a blog, and in particular that I had mentioned NPR. And now I can tell you about it using the blog. Dizzying.

A little late

Congratulations to Howard Dean for winning his first primary.

So Kerry is the nominee. From Fark.com (somewhat indirectly, since they mangled the link) comes the news that he wants to be our second black president:

Speaking to the American Urban Radio Network, Kerry said Monday that he hoped to emulate former President Clinton in the eyes of blacks, the party's most loyal constituency and a solid source of support during his stretch of primary wins.

"President Clinton was often known as the first black president," Kerry said. "I wouldn't be upset if I could earn the right to be the second."

Now we can look forward to a stream of articles speculating about the veep slot, followed by a compensating stream telling us it doesn't matter because the vice-presidential candidate can rarely even help win their home state. (Of course, Gore couldn't win his home state in 2000, so maybe the presidential candidate doesn't matter either.)

Nobody's really excited about Kerry, are they? He seems like Gore with a different accent. Aloof, drifting, only predictable in his willingness to back down on questions of principle when an opportunity to pander presents itself. But we should give him a chance, and see how he does under the spotlight of the general-election campaign.

Tuesday, March 02, 2004
Water on Mars

So it looks like there used to be a lot of water on Mars.

This is a great discovery. There's so much we don't know about the origin and evolution of planets and their chemistry, any little bit of information helps. The evidence seems to be somewhat indirect (sulfate concentrations, shapes of rocks), but I'm willing to believe that it paints a compelling picture.

Still, I have profoundly mixed feelings about this. Of course, the result is immediately spun as evidence for the possibility of life, with some intentional ambiguity about how strong the possibility is, when the life might have died out, or what form it took. More than one of the scientists comes right out and says that this part of Mars would have been an hospitable environment for life to exist. Really? Just because there was water? Wouldn't we need to know a little more than that to make such a sweeping statement?

Discovering solid evidence for life native to Mars (as opposed to some organic material that was splashed there from Earth, as we now know can happen after comets or meteors impact us) would be a truly wonderful event. But it's not very likely. For one thing, it's just hard; I can imagine a long series of experiments reaching inconclusive results. For another, the a priori chances that life evolved separately on Mars seem incredibly small. There seem to be a lot of planets in our galaxy (one hundred billion, maybe?), but yet the galaxy is not teeming with the electromagnetic buzz of numerous advanced civilizations (the Fermi paradox). Either civilizations destroy themselves with extremely high probability, or life comes into existence with extremely low probability. Choose for yourself which seems more reasonable.

But still, it would be well worth chasing after this remote possibility if it didn't cost anything. (Warning: curmudgeonly realism ahead.) But this finding will certainly be used as justification for funneling yet more money away from other NASA science programs and into the Mars program, especially into the manned mission which Bush recently proposed. Which is just silly.

The space shuttle and the space station were part of a NASA strategy to make travel to Earth orbit cheap and routine, which is certainly a laudable and achievable goal. The problem is, it's been an abject failure. Shuttle missions are infrequent, unsafe, and fantastically expensive; the space station is even worse on all counts. So the new strategy is to build a base on the Moon and then visit Mars? This is like a kid who can't quite get the hang of riding a bike without any training wheels, who decides that everything would improve if he enters the Tour de France. Not that it's not a worthwhile goal (either the Moon or the Tour de France), but it's not necessarily right under any circumstances. And we're just not there yet.

Meanwhile, the rest of NASA's science budget is being strangled. I gave a colloquium at the Space Telescope Science Institute on January 14th this year; the starting time had to be delayed so that everyone could listen to the President's announcement of the new initiative, which had been (coincidentally, one assumes) scheduled for the same time. The sense of dread in the room was palpable; here were dozens of dedicated scientists, who were devoted to using this fantastic instrument to discover new things about the universe, who could see it being undermined before their eyes. And indeed, soon thereafter the planned servicing mission (to install $200 million of new equipment, which has already been built) was canceled. Safety was certainly a major concern in the decision, but money was a crucial factor.

And Hubble is not the only thing to go. I was recently on a NASA "roadmap team" to sketch out a future plan of missions in cosmology and astrophysics. We came up with the Beyond Einstein program, an ambitious but practical set of missions to learn about black holes, dark matter, dark energy, and the early universe. In the President's new budget, all of the new missions were pushed back several years; of course they can continually be pushed back until they never happen. I have a vested interest in this kind of science, it's true; but by any objective measure the most successful science missions that NASA has done have been unmanned satellites, not sending people around the solar system. Our scientific decisions are being increasingly driven by spectacle and political calculation, which is a shame when there are such exciting results potentially within reach.

It's terrible that I can't simply enjoy a wonderful scientific result for what it is, but automatically start fretting about the wider political consequences. Must be a grownup or something.

Subway books

On NPR this morning, a teaser for The World mentioned a story this afternoon about a new program in Mexico: they are going to hand out free books to people riding the subway. (Here's a version of the story from Newsday.) Apparently Mexico has the highest literacy rate in Latin America (about 90%), but people don't really spend that much time actually reading, so the program make it easy for people to read in a context where they can't do much else. Hopefully the reading will catch on, maybe even cut down on crime in the subways.

Now, as an idealistic liberal, this sounds like pure genius to me. But realistically there are a couple of questions. First, is this really going to work, or is it just a fantasy cooked up by Mexican liberals who are as starry-eyed and idealistic as I am? Second, who chooses the books? From the story it appears that they are publishing special books of short stories for the occasion, but someone has to decide who gets included. Can you imagine the political (or even literary) wranglings over that one?

So far only about 64 percent of the books have been returned. That doesn't sound so bad, actually, and I can imagine that people will quit swiping them if they are consistently available for free on the subways. Besides, it's kind of encouraging that people would want to steal books at all.

Monday, March 01, 2004
Vicissitudes of Fame

The first time I've ever seen a paper with my name in the title, and they manage to get the spelling wrong. Now I know how Zbigniew Brzezinski must have felt all the time.

Meanwhile, I seem to have attracted almost a hundred visitors on my first blogday. This internet thing, as others have already noticed, just might catch on. But I don't know how to tell where people come from, or which pages are linking to me; I think blogspot won't reveal this information unless I pay them money.

[Update: Now I know how to find who's linking where. It's all at Technorati.com, but you probably knew that. Thanks to Henry Farrell of Crooked Timber for the tip. (I still think it takes cash to figure out which visitors came from where.)]

Moments in Atheism

This quarter Shadi Bartsch and I are teaching Moments in Atheism, an undergraduate course in the Big Problems curriculum here at the University of Chicago. I'm not sure what is more surprising, the idea of a course on the history of atheism, or the fact that I could get a humanities course to count as a regular teaching credit.

Teaching the course has been a fantastic experience; it brings me back to my own days as an undergraduate, exploring great ideas in philosophy and history. Indeed, one of the interesting things we have realized along the way is how much the history of atheism parallels all of the major twists and turns in the intellectual history of Western civilization generally. This has to be one of the few courses ever taught with Thomas Aquinas, Karl Marx, and Stephen Hawking on the same syllabus.

We were concerned at first about the touchy nature of the material; we wanted everyone to feel comfortable, no matter what their personal beliefs about religion were. So far it seems to be a success; there is a range of views represented in the class, and nobody has yet complained (out loud, anyway) about being marginalized.

One interesting discovery is the paucity of scholarly work on the actual history of atheism. It's easy enough to find polemical books on either side of the issue, or careful philosophical works for and against the existence of God, but there's not so much done on how the ideas have actually developed through time. Maybe because it's a touchy subject? Also fascinating how reluctant people were to declare themselves atheists (until the 19th century), no matter how obviously the implications of their work were pushing them in that direction. Up at least through Hume, the pressure was so great that nobody could admit to disbelieving in God, even if they thought He was completely powerless in the world, or equal to the world.

Unfortunately we didn't have time to do much about the present day. It's still a touchy subject, of course; probably as much now as two hundred years ago. The elder George Bush famously said that he didn't think that atheists should be considered as citizens. I'm not sure why the US and Europe seem to have diverged so dramatically on this.

Milestone reached

My first link, from Pharyngula (thanks!), who was understandably disappointed that I wasn't the other Sean Carroll, an evolutionary biologist at the University of Wisconsin. I've never met the other SC in person, although I do remember a moment about ten years ago when I found an article in Time magazine about the nation's 50 brightest minds under the age of 40. I picked it up, optimistically searching for my own name, and much to my surprise there it was! Only, attached to a different person. Just last year we were both interviewed by the BBC on the same program (about different science topics). But my site comes up first on Google, so there.

Ideas on culture, science, politics.
Sean Carroll

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