Preposterous Universe

Sunday, February 20, 2005
AAAS report

I'm back from the annual meeting of the American Association for the Advancement of Science, which was held this year in Washington, DC. The AAAS is a useful organization whose existence is largely ignored by physicists. Their most obvious contribution is publishing Science, which (like its UK counterpart Nature) tends to deal more with biology, chemistry, medicine, and the environment than with physics. The annual meetings reflect this emphasis; physics is only a tiny part of the proceedings, although some of us would like to see it be more prominent.

The thing that separates AAAS from professional societies such as the American Physical Society or American Astronomical Society is the word advancement. The AAAS is especially concerned with the interactions between science and the outside world -- through education, public policy, and media outreach. One of the main purposes of the annual meeting (maybe the main purpose) is to bring scientists in contact with interested journalists. Something that surprised me when I first realized it, but seems obvious in retrospect, is that science journalists don't typically have the luxury of flying around to topical conferences to get a feel for what is interesting within some specialized field. Except at the very largest outlets, most science writers have to pore through press releases to find their stories; if they're especially dedicated, they may scan Science or Nature or even the arxiv, but those are the exceptions. So the AAAS meeting provides a nice opportunity for scientists and journalists to mingle in the flesh; not coincidentally, the annual meeting of the National Association of Science Writers is usually held in conjunction with the AAAS.

(I won't even bother to make the argument that it is good for scientists and journalists to mingle -- good for science, and good for the interested public [which is most of the public]. Some scientists stay away from journalists because they think they won't be taken seriously if they appear in the media, and some are quite explicitly disparaging of their colleagues who do. That's a rant for another day.)

My main role this year was as the organizer of a symposium on Understanding Dark Energy. (That's a link to the symposium web page I set up; you can also read our press release, or the symposium summary in pdf.) I thought it was successful, with maybe 150 people in the audience. We had three hours and six speakers, so the talks were short and sweet. I opened with a brief description of why we believe in dark energy, what the theoretical puzzles are that we are trying to solve, and the things we hope to learn from new experiments. Adam Riess went next; Adam was the lead author on the first of the 1998 papers that presented evidence for an accelerating universe from observations of high-redshift supernovae. He talked about the future of supernova cosmology, both from ground-based and space-based observations, and how we can simultaneously constrain the equation-of-state parameter w and its time derivative. Lenny Susskind went next, saying how happy he was to be at an AAAS meeting giving a talk on biology. That's because he went on to compare the number of possible vacua of string theory (the "landscape") to the number of possible biological organisms you could get by arranging base pairs in a DNA molecule -- the former is perhaps 10500, while the latter is maybe 1025000000000. So biology wins, but the lesson we are supposed to learn is that a large variety of possibilities is what enables the development of intelligent life; in the context of string theory, it is the large number of stable vacua that makes it possible to find one with a sufficiently small vacuum energy so that life can evolve. (This is the press release that Peter Woit was lamenting.)

Next up was Licia Verde, talking about what we could learn from structure in the universe, combining constraints from early times (the cosmic microwave background) and late times (galaxy surveys). She had a nice analogy with waves on the ocean, driven by wind until they become non-linear and interesting to surfers: if the ocean were made of honey, the waves would evolve quite differently. Likewise, structure in the universe evolves in a way that depends on the underlying constituents, which can be used to discover properties of dark matter and dark energy. Switching back to outlandish speculations, Gia Dvali talked about how we could get an accelerating universe even without dark energy, if gravity were modified on large scales. An important point from his talk is that you can never modify gravity only on cosmological scales -- effects always leak down to smaller distances. In the case of a simple theory like mine, these effects are dramatic, and rule out the model definitively. In the case of a more subtle theory like Gia's, the effects are less pronounced, and the model is not yet ruled out; but it is certainly testable, especially by high-precision measurements of the orbit of the Moon. We closed with a fantastic talk by John Carlstrom, who described how clusters of galaxies will be a new method to probe the expansion history of the universe. John is the world's expert at observing the Sunyaev-Zeldovich effect, the scattering of microwave-background photons by the hot gas in galaxy clusters. Since what you observe in the SZ effect is a shadow on the CMB rather than the direct emission of light, the effect does not diminish as the clusters get farther away -- they can be found at any redshift, and the rate at which they assemble as a function of time reveals a lot about the way the universe evolved. John and his collaborators are building two impressive projects to make SZ surveys: an array of eight telescopes in California, and one giant radio telescope at the South Pole (a similar project, the Atacama Cosmology Telescope, is also underway in Chile). With all these new data coming in, it won't be surprising if theorists are once again startled by something we discover in the real world.

There are a plethora of different symposia at the AAAS, and the sexiest and most media-friendly are granted separate press conferences. For some reason, the press briefings are held before the symposia themselves; this gives reporters the feeling that they have first access to the news, but it means that they are asking questions before they've actually heard the talks. Still, we had a well-attended and sprightly press briefing. Since we didn't announce any stunning new results, I think the effect will be largely in the background, helping journalists understand what is going on and preparing them for future discoveries. But there have already been a couple of stories, prompted by those wild theoretical ideas: one on the landscape, and one on modified gravity. (Update: Here's another, from Astronomy magazine.)

Somehow I was also involved with another press conference, this one as part of the celebration of Einstein's miraculous decade, 1905-1915. Einstein started off the decade with three spectacular papers, any one of which would be the highlight of the career of an ordinary physicist: explaining Brownian motion in terms of atoms, inventing the photon as an explanation for the photoelectric effect, and establishing special relativity. But he was just getting started, and ten years later he came out with his capstone achievement, the general theory of relativity. The other panelists for this briefing were Rolf Sinclair, Richard Wolfson, and Barry Barish. (The three of them also appeared on Science Friday with Ira Flatow, while I was busy at the dark energy symposium.) The highlight of this briefing was the unveiling of Einstein@Home, a screensaver program that uses your unwanted CPU cycles to look for signals of spinning pulsars in real data from LIGO, the Laser Interferometric Gravitational-Wave Observatory. Barry introduced Bruce Allen of the University of Wisconsin-Milwaukee, who has been instrumental in developing the Einstein@Home software. The ultimate pay-off is not quite as exciting as for SETI@Home, but the likelihood of actually finding something is much higher!

Barry Barish, by the way, is one of the most impressive physicists you will ever meet. He was trained as a particle physicist, and did some of the first experiments to discover weak neutral currents, key to the Glashow-Weinberg-Salam model of the electroweak interactions. And now, having smoothly shifted gears, he is Director of the LIGO laboratory. But Barry hasn't forgotten about particle physics; he is extremely active in planning for future experiments, most recently as the head of the committee to decide on the basic technology for the planned International Linear Collider, the hoped-for follow-up to the Large Hadron Collider. He gave a great talk at a session on high-energy colliders, in which he explained the process by which the committee decided on the "cold" (superconducting) option rather than the "warm" option. The miracle is how quickly the worldwide community has dropped what they were doing to rally around this decision; that wasn't so hard for the folks at DESY in Germany who had developed the superconducting technology (TESLA) in the first place, but the people in Japan and at SLAC who were pushing for the warm technology were also very quick to get on board once the decision had been made. Now all that remains is to figure out where to build it (outside Fermilab would make sense), and who will pay. (For info on the current climate, see comments at Peter's blog.) The total cost is estimated to come in around five to eight billion dollars, which for comparison purposes is about one percent the cost of a manned mission to Mars.

My final event at AAAS was a TV interview with ScienCentral. This is an interesting outfit that makes short science stories, then sells them to other media outlets (like your local news program). They interview you on tape for half an hour or so, and then will chop it up into TV-sized morsels afterwards. (After some practice, I'm pretty comfortable on radio and TV by now, but I still need work on speaking in sound bites instead of elaborate paragraphs.) The woman interviewing me, Joyce Gramza, was initially skeptical about the whole cosmology thing, since she had just finished a bunch of interviews with scientists whose work actually had a tangible impact, like getting flu shots to people. Of course science does have an important impact on our daily lives, but that's not the whole point of it -- there's also the straightforward human pleasure of learning about the universe around us. Most people will accept that if you tell it to them honestly, rather than trying to pretend that we really study dark energy because it will someday lead to a cure for cancer. Joyce seemed to buy my argument, and by the end was saying that I should get my own show, which was nice of her. She also complained that she was interested in mathematics and physics as a student, but was consistently discouraged from studying them because she was a girl. I guess she just wasn't honest enough with herself to admit that she probably didn't have the intrinsic aptitude that us boys are blessed with.

One of the pleasures of combining a big meeting like the AAAS with a power center like DC is that you keep bumping into celebrities. I ran into Shirley Ann Jackson, who is President of the AAAS and also of Rensselaer Polytechnic Institute (I guess she hasn't been honest with herself either). And I went to a panel discussion on how to write and sell popular-level science books, which featured none other than John Derbyshire. Okay, he's not really a celebrity outside the blogosphere, but still. He was generally charming in an English-public-school sort of way; but no mention of LSD trips, and I didn't have the heart to ask. Finally, as I was heading out of my hotel I noticed Ralph Nader in the lobby chatting with some people. He's taller than he seems on TV.

I almost didn't write this post because I thought there wasn't that much to say. But I see I've gone on at unseemly length. This is what you get when I have an hour to kill in the airport before my flight back to Chicago.

Ideas on culture, science, politics.
Sean Carroll

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