Tuesday, August 31, 2004
Testing general relativity
Some slightly-recycled content. (But it's new to you, right?) Science writer Amanda Gefter is working on an article for Sky and Telescope about testing general relativity. (See other articles by Amanda here and here.) She emailed me to ask some general questions about the state of GR and its experimental tests; here are the questions and my answers, just off the top of my head.
What are scalar-tensor theories of gravity? In these theories, where does the extra field come from (in other words, what is it, and why is it there?) How do these theories modify GR? If a scalar-tensor theory is found to explain experimental results, does that necessarily mean that there are extra dimensions? How viable do you think these theories are?
Scalar-tensor theories are simply generalizations of GR that add a new scalar field that interacts directly with gravity (i.e., couples directly to the curvature of spacetime). A scalar field is like the electromagnetic field, except that it only has a magnitude and not a direction; it simply takes on a single numerical value at each point in spacetime. The first scalar-tensor theories proposed that the gravitational constant, which fixes the strength of gravity, could have a variable strength that depended on some scalar field; but current theories are more general.
Scalar fields can arise in different ways. Often, they are simply put there. They can also arise from extra dimensions of spacetime, or from superstring theory. But if we find a scalar field, it certainly doesn't imply the existence of extra dimensions, as there are many other ways to get such scalars.
Scalar-tensor theories are simple and natural generalizations of GR, and it wouldn't be surprising if one of them were true. However, many theories that are studied in the literature assume that the scalar field is very light, and therefore leads to (potentially detectable) effects at large distances. It's much more likely that any such scalar has a significant mass, perhaps near the Planck scale, and so would remain undetectable in any conceivable experiment. However, we know little for sure, so it pays to keep an open mind.
Are there other alternatives to GR that are being explored? Any that you find particularly promising?
There are many alternatives being explored, too many to list or even catalogue. The most straightforward, and perhaps most promising, imagine that something like GR is true in extra dimensions, and lead to a modified theory at the level of our observed four-dimensional spacetime. The ways in which this theory can be modified will depend in the specific model of extra dimensions; it has been proposed that such theories can help explain the value of the cosmological constant, or explain the acceleration of the universe without any cosmological constant, or affect cosmology at very early times. It is also possible to modify GR directly in four dimensions to help do away with the need for dark energy.
Other models try to do away with the need for dark matter, by modifying gravity on the scale of galaxies. A famous example is MOND (Modification Of Newtonian Dynamics) by Milgrom, although that is more of an "idea" than a "theory" (although Bekenstein has recently tried to put it on a more sound footing). The biggest problem with such models is that they have a very hard time reproducing the many successes of the dark matter idea, for example in accounting for the perturbation spectrum of the cosmic microwave background.
Finally, there are models that don't try to explain some specific feature of astrophysical observations, but instead simply try to see how far we can go in modifying GR. For example, there are models which violate Lorentz invariance at a fundamental level. These are interesting to explore, if only to help us understand the extent to which GR can be trusted.
Why is it important for us to test GR? Has it become more imperative in recent years?
Gravity is an important force, and GR is our best theory of gravity, so it should be tested as well as we possibly can. More specifically, cosmological observations (dark matter, dark energy, and primordial perturbations) have revealed a universe that seems very surprising to us, and our interpretations of these observations rely on extrapolating ordinary GR to scales of time and distance that are far larger than where it has been directly tested. So any new tests can give us more confidence that we have the right to make such extrapolations.
Why is our understanding of gravity so important?
See above. On the large scales characteristic of cosmology, gravity is by far the most important force. In addition, it is the only force that has thus far evaded a quantum-mechanical understanding; reconciling GR with quantum mechanics is the greatest single quest in contemporary fundamental physics, and any information we have about gravity itself could be an invaluable clue along the way.
Up to this point, is GR a well-tested theory?
It is extremely well-tested in certain regimes, less so in others. Three regimes have been especially well-tested: the Solar System, where precision measurements have tightly constrained deviations from GR; the binary pulsar, whose orbit implies exactly the amount of gravitational radiation predicted by GR; and the early universe, where observations of light elements produced by nucleosynthesis and the anisotropies of the cosmic microwave background provide good evidence for the validity of GR when the universe was seconds old and hundreds of thousands of years old, respectively.
There is still a lot we don't know. For example, are the predictions of GR for gravitational lensing and dynamical measures of mass consistent with each other? Are there deviations at very strong curvatures, or for that matter very weak curvatures? Are there deviations at very small distances that may be probed in the laboratory? (Current best limits go down to about one tenth of a millimeter.) Are there long-range but subtle effects that still may show up in the Solar System?
As I understand it, GR has been inadequately tested in the strong field regime. Why is it important to test GR in such extreme circumstances? What kinds of tests will be helpful? In particular, how can we use black holes to test GR?
I wouldn't say "inadequately", but we can always do better. To be honest, I think that testing GR with black holes is interesting, but somewhat overrated. If GR is going to be modified, there are two likely ways it can happen: subtle long-range effects, and deviations that become important when the curvature of spacetime reaches a certain fixed value. In the first case, Solar System tests will usually do better than astrophysical tests, just because the precision is higher. In the second case, we would have to get extremely lucky indeed to notice any effects in black holes. The curvature outside astrophysical-sized black holes is actually not that great; the curvature radius would be measured in kilometers, while we would probably need to go to much smaller scales to observe any deviations from general relativity.
On the other hand, as already mentioned it's important to keep an open mind. Many of our tests of GR thus far have either been in cosmology or in the quasi-static, weak-field regime of the Solar System, with the binary pulsar being the notable exception. Even if our most respectable alternative theories wouldn't necessarily show up first in a dynamical, strong-field situation, we should certainly do as many tests in such regimes as we can, if only to make sure there are no surprises.
Is it strange to use black holes as testing grounds for GR when they them selves are consequences of the theory of GR? (in other words, if GR were wrong, would there even be black holes?)
Most respectable theories of gravity (all that I know of, to be honest) predict that there should be black holes, although their properties might be different in different models. So they are well worth investigating, keeping in mind the previous answer.
I understand you worked with Ed Guinan on DI Herculis -- what are your thoughts on that problem? Do you think it points to a gap in GR, or is it an experimental anomaly? Are physicists worried about it?
It's a very interesting system, and I don't know what is going on. I became skeptical that gravity is to blame when I worked out that the stars in DI Her are well within the weak-field regime where Solar System tests have already tightly constrained any possible deviations from GR; it seems very hard indeed to find a theory that could explain the motion of DI Her yet remain consistent with Solar-System tests. So I suspect that some astrophysical phenomenon is causing the discrepancy, but I'm by no means certain.
Have there been any other observations that seem to violate GR?
It's hard to say that any given observation violates GR, since there are always other assumptions that come into play. For example, the anomalous acceleration of the Pioneer spacecraft may be due to some extremely unexpected gravitational effect; more likely, however, there is some much more mundane explanation involving the spacecraft themselves. So far, there is certainly nothing we have observed that gives anything like a good reason to doubt GR.
In your opinion, what have been the most significant tests of GR?
Historically: precession of Mercury, deflection of light, gravitational redshift, and gravitational time delay. More recently: the binary pulsar and cosmological nucleosynthesis.
Any thoughts on the importance of Gravity Probe-B? Lunar laser ranging?
GPB is in a somewhat awkward position; it will either confirm the GR prediction for frame-dragging, or it will find a discrepancy and very few people will believe it. I'm not an expert, but my understanding is that the regime it is testing (in the "parameterized post-Newtonian" sense) has already been ruled out by other observations.
Lunar laser ranging is a very different story, well worth doing. There is an opportunity to greatly improve the precision of constraints on long-range deviations from GR, which is always interesting, even if there is no firm prediction from a specific model.
Will the detection of gravity waves be an important confirmation of GR?
Yes, absolutely. At this point, however, very few people doubt that gravitational waves exist, with essentially the properties predicted by GR, so they are more looking forward to learning about the astrophysical sources of the waves. If the observations are somehow inconsistent with GR, that would be an even more spectacular finding than anyone expects.
What makes general relativity such a beautiful theory?
It is extremely powerful (accounting for all gravitational phenomena ever observed), mathematically compelling (applying elegant results from differential geometry), and remarkably simple and robust (unlike, say, the Standard Model of particle physics). GR is simply the statement that "Gravitation is the curvature of spacetime", made precise and mathematical; few theories in science are simultaneously so simple, elegant, and comprehensive.
Finally, do you think that GR will ultimately prove to be wrong (or incomplete) at some level?
Yes. Everybody (in their right mind) does. GR is a classical theory, fundamentally inconsistent with the quantum world in which we live. At the very least we will have to find a quantum version of GR; more likely, we will have to find some more profound theory that is intrinsically quantum-mechanical and reduces to GR in the appropriate circumstances. If experiments reveal deviations from GR at even the classical level, so much the better.
Monday, August 30, 2004
The nice thing about jet lag after a long trip westward (say, from Austria to the U.S.) is that you wake up early enough to enjoy the morning, something I tend not normally to do. Which is why it's too bad I am not still in my beloved Chicago enjoying a cup of coffee while watching the sun rise over Lake Michigan, but instead sitting in a hotel room in Riverside, California, site (Riverside, not my hotel room) of the annual meeting of the Division of Particles and Fields of the American Physical Society. Tuesday afternoon I'll be giving a review talk on "Theoretical Cosmology," which sounds a bit too comprehensive to be coherent, but we'll give it a go. Since it's the last talk of the conference, likely nobody will be in the audience; if I remember I'll post a link to the slides (once, you know, they've been written).
In the meantime, I'll share this. Poet Richard O'Connell was kind enough to email me a copy of this poem he wrote in 1976:
To Beta, Cosmically ConsideredMaybe I can figure out some way to work it into the talk.
Also, read about a Big Bang in your bedroom. (No, it's not what you think.) I will explain later.
Sunday, August 29, 2004
I remember, back in 1992 when the Dream Team of NBA stars first participated in the Olympics, someone telling me with a straight face that the US would never lose a basketball game in international competition again. Why not? Because basketball is a black person's sport, and the Europeans and South Americans just couldn't compete athletically.
Someone forgot to tell the Argentinians and Italians, as the former beat the latter for the gold medal yesterday. The US managed to squeak by a small former Soviet republic to claim the bronze. The team played hard, but was under-prepared and put together badly for this kind of competition, with a bunch of swingmen who can drive to the basket and a significant lack of big men and outside shooters.
Who comes out of the fiasco looking the best, from the US side? None other than poster boy for selfishness Allen Iverson.
Like Lindsay, I don't really care that much about the Olympics. But it was sad to hear that the US team went from being worshipped a decade ago to being booed off the court this year. Of course, that might have something to do with issues other than basketball.
Saturday, August 28, 2004
From Europe to America
I'm back from the European Forum in Alpbach (where I was referred to as "herzig," which I think is good). Many thanks to Lindsay for keeping things active while I was away. Only after getting there did I understand what the Forum is about, partly because it is such a sprawling multi-dimensional thing that a focus can be hard to pinpoint. There are many events involving all sorts of discussions on politics, culture, and anything else (science is represented, but only as an amusing distraction). The seminar week, which is what I was there for, is almost a summer school; twelve seminars go on for a week of lectures, and about three hundred students (largely graduate and professional students) from throughout Europe come to listen and participate in the discussions. But the definition of "student" is pretty loose, and a good number were well past their student days.
What became clear only gradually was that, since most of the students are interested in public policy questions, many of the attendees are there largely to network amongst their fellow students, rather than to actually attend the seminars. And the seminars they did attend were those that related in some way to their careers; i.e. questions of European politics. So everyone was interested in our little cosmology discussion, but very few people actually came to it.
That's okay, since you can still learn interesting things by talking to the other attendees. Issues of the European Union were especially popular, for understandable reasons. Someone gave me an article to read by Stephen Breyer, my favorite Supreme Court Justice (although if Kathleen Sullivan is ever appointed, she will be granted this coveted honor), musing about the new European Constitution. It was fascinating reading, especially because Breyer was trying very hard to be polite but clearly has substantial worries about the new document.
One of his worries is obvious: the new constitution is far too long (about eighty percent of it should be cut, in Breyer's estimation). In an effort to keep everybody happy, the framers have stuck all sorts of things into the constitution that should be ordinary law. One of the crucial features of a constitution is that it should be possible, but very hard and extremely rare, to amend it; so it should stick to enshrining absolutely bedrock principles rather than including every policy we might agree upon at the moment. (He also points out that the European court will have over twenty justices, speaking multiple languages, and can't resist mentioning the difficulty that he and his eight very capable colleagues sometimes have in reaching consensus, even in a common language.)
The more subtle of Breyer's points is the ease with which the constitution will allow centralization of power. From personal experience, he knows how ambiguous language in a constitution can be interpreted to funnel more authority to the federal government. He mentions the example of education, where the constitution innocently gives the European Commission power to pass rules to facilitate cooperation and compatibility between the educational systems of the member states. Who could object? Well, cooperation takes a lot of forms -- Breyer imagines that before too long the EC will be passing whatever regulations it likes on school systems throughout Europe, all in the name of increased cooperation. It will be interesting to see how the constitution actually fares in action (although they did manage to keep Christianity out of the preamble, despite heavy Papal lobbying).
So, while we're at it, do Europeans hate Americans? Well, the participants at Alpbach are traditionally conservative, establishment-oriented types, who generally are more pro-American than their lefty counterparts. But one over-simplified way to describe the current situation is that both left-wing and right-wing Europeans are horrified by our current administration. They don't hate Americans, but the disgust with the Bush regime is palpable. Of course, these are people who will willingly sit through hours of discussion and dialogue relating intricate philosophical questions to concrete issues of policy; something tells me Bush wouldn't like them, either.
Friday, August 27, 2004
Role reversal (or, the trouble with state societies)
Remember the good old days when big men secured political power by throwing huge parties for ordinary people? I don't--but the brilliant Dr. Cathy D'Andrea taught me all about these bygone ceremonial redistributions in Archaeology 101. I refer skeptics such fine ethnographic films as Ongka's Big Moka, or online exhibitions like Harvard's Gifting and Feasting in the Northwest Coast Potlatch.
American politicians used appreciate the value of a good political party. The Randy Newman song Kingfish gives the gist:
Who gave a party at the Roosevelt Hotel?
And invited the whole north half of the state down there for free
The people in the city
Had their eyes bugging out
Cause everyone of you
Looked just like me
Many pre-state societies have used lavish ritualized redistribution ceremonies to cement political influence. Time was when a leader had to publicly redistribute wealth by sponsoring massive public consumption. In many ways this was a more civilized and agreeable arrangement. Before lawyers and contracts, the great chiefs of the Pacific Coast would cement important claims with potlatches--extravagant festivals of gifting, feasting, and dancing. People came for the presents and stayed for the ceremonial boasting. The better the party, the higher the turnout. The bigger the crowd, the more people "on message" about the new fishing ground or the latest dynastic marriage.
Unfortunately, public gifting is obsolete in state societies. Vote buying has become so boring and impersonal. Ads have replaced dances. Free booze has given way to promises of drug benefits.
One of the little-noted drawbacks of modern life is that citizens now have to throw lavish parties in order to impress politicians. Consider the opulent celebrations surrounding the Republican National Convention [NYT permalink]. The "notoriously frugal" Bush campaign isn't shelling out to show the faithful a good time. This week the lobbyists are treating:
At Cartier, guests can shop while they mingle and munch with lawmakers. There will be dinners at Per Se and Daniel. Conventiongoers will cruise New York Harbor at midnight and gather on the flight deck of the U.S.S. Intrepid, a retired aircraft carrier docked in the Hudson River at 46th Street. And official Washington will, of course, be treated to some of the most elaborate events, sponsored by companies such as General Motors, Boeing, American Express and scores of others.
I wouldn't mind the RNC if Zell Miller gave me a button blanket emblazoned with my family crest, or even a martini at Tavern on the Green. If this were Papua New Guinea, George W. Bush would slaughter thousands of fattened hogs and invite all of New York to feast on the Great Lawn of Central Park. This year, all we get is a court order to keep off the grass.
[X-posted with Majikthise.]
Prison tats of Texas: Photo Essay
Prison Tatoos of Texas a photo essay by Andrew Lichtenstein, published in Foto8.
Thursday, August 26, 2004
Subjective, intersubjective, objective Olympiad
Dan Drezner approvingly quotes Sport's Illustrated's Josh Elliott:
No athletic event that is judged belongs in the Olympics. And no exceptions: No gymnastics. No ice skating or boxing. No synchronized swimming or diving. If it can't be won on the track, in the lane lines or with one more goal than the other folks, it has no place in the world's premier festival of sport, one that purports to give us the world's greatest champions. For if a win can't be unquestionably achieved, what's it worth, really? Without an objective, inarguable method for determining victory and defeat, the very meaning of the competition is lost.
A judged win can be worth just as much as an objective win. It all depends on how much we respect the opinions of the judges. Furthermore, human judges can assess nuances of performance that a one-criterion objective competition can't capture. It's easy to see why people compete for other judged honors, e.g. the Nobel Prize, the Pulitzer, or the John Bates Clark Medal. So, it should be clear why Olympic gold is meaningful to divers, figure skaters, and gymnasts.
Expert decisions are always vulnerable charges of arbitrariness, bias, and favoritism, especially if the contest includes an aesthetic component. Yet we keep watching if we trust the judges and the institutions that appoint them. We can also use objective methods to audit many kinds of judging. Olympic judges are supposed to be judging according to objective criteria and established aesthetic norms. There's an irreducibly subjective component to some judged contests, but, as Matt Yglesias observes, the judge's primary role is to apply the public rules and standards of the sport. We are entitled to expect a fair bit of intersubjectivity in judged verdicts. If we have doubts, we can use objective methods to test the standardization. At the very least, judges are constrained by the prevailing standards of their field. Their status as honest experts is contingent upon a fair amount of agreement between their verdicts, those of their peers, the objective evidence, and educated opinion.
Maybe some Olympic sports are too tarnished for credible judged competitions. If so, that's indictment of the Olympics, not a reason to dismiss all judged competition.
Perhaps anticipating objections like mine, Drezner adds:
This doesn't mean that judged competitions aren't exciting. Gymnastics, diving, ice skating can be entertaining, and they demand physical excellence -- but they're not sports.
Drezner is arguing that objective judging is integral to the nature of sport. When Belle Waring complains about idle essentialism kind of essentialism, Drezner replies that her Wittgensteinian worries are misplaced because his only proposing objectivity as one necessary condition for being a sport and rather than proposing a set of necessary and sufficient conditions for being a sport.
Even so, Drezner hasn't defended his necessary condition against charges of arbitrariness and/or disregard for ordinary language. We could stipulate that the term "sport" applies only to athletic competitions decided objectively. But why should we? To do so would disregard ordinary English without clarifying anything. Everyone agrees that Olympic divers and gymnasts are competitive athletes. So, if diving and gymnastics aren't sports, what are they? They're not exactly games and they're more than pass times. So far, we don't have an English paraphrase that captures the idea of "competitive physical pursuits adjudicated by judges." Drezner might argue that we ought to coin a term for these judged events, but he hasn't explained why such a revision would be desirable, let alone necessary.
Maybe Drezner is using the term "sport" honorifically. That is, maybe he is arguing that objectively adjudicated events are more valuable than their judged counterparts. If so, he owes us a more detailed argument for that claim.
The potential weaknesses of expert judging are well known, and there is something reassuring about an objective, transparent standard of excellence that anyone with a stopwatch and a camera can verify. However, some might argue that the value of objective Olympic competitions is being undermined by rampant abuse of banned substances. Yes, the standard of victory is clear, but the standard of fair play is becoming increasingly murky.
By contrast, judged competitions may remain interesting in an age of chemically enhanced sport. I'm sure there are gymnasts who abuse banned substances, but a great gymnastics performance makes aesthetic and intellectual demands on the whole person. It's boring to watch the 100 meter dash when you suspect that some of the athletes are dirty. All that matters is who crosses that line first. A chemically enhanced gymnastics routine is still cheating, but at least there's some point in watching it on its own terms. As far as I know, there aren't no good-taste- and innovation-enhancing substances.
We seem to be rapidly approaching the limits of human performance in many objective events. Many judged events will continue to evolve technically and aesthetically long after 100 meter times have leveled off. By choosing his events and his routine, a clean gymnast might be able to compete against a drug user by dint of innovation, aesthetics, and natural athleticism. In judged events, individual athletes can accentuate their strengths and compensate for their weaknesses in order to deliver their best possible performance. These the kinds of physical and mental virtues that athletic competition ought to celebrate.
Frankly, I have a hard time caring about the Olympics at all. But, if we're going to reject the Olympics, it should for institutional corruption, hypocrisy, greed, and cultural irrelevance. Let's not take it out on the gymnasts.
[x-posted with Majikthise]
Addresssing Big Pharma publication bias
Bravo, Eliot Spitzer:
In a settlement that the New York State attorney general said would transform the drug industry, GlaxoSmithKline agreed today to post on its Web site the results of all clinical trials involving its drugs.
Underreporting of unfavorable trials is a threat to in clinical research. All scientists have some incentive to publish favorable results over unfavorable ones, but the potential for systemic bias is magnified when big companies insert themselves into scientific research. A single unfavorable trial of a promising new drug can send a company's shares tumbling. It's not just company scientists whose work is affected. Independent researchers who are becoming increasingly dependent upon research grants from pharmaceutical companies. These grants may restrict investigators from publishing unfavorable findings. Big pharma will spare no expense to create data on a potential blockbuster. Unlike most academics, these companies can afford to keep sponsoring trials until they get the results they want. Increased transparency is the only way to safeguard the scientific record against distortion on a major scale.
I'm glad to see Spitzer taking the lead on disclosure for clinical trials. This isn't just about consumer protection, academic integrity, or the flow of information in a free market. Selective publication is also undermining the credibility and comprehensiveness of large swathes of the biomedical literature. Over time, systematically skewed incentives distort the scientific record. The worry is not just that some bad drugs may come off looking good. The problem is far more serious. Corporate publication bias has the potential to distort the scientific record and thereby to impede scientific progress on a larger scale.
Philosopher Susan Haack has famously compared science to a partially completed crossword puzzle. Each answer constrains subsequent answers. Our willingness to entertain subsequent answers to depends, in part, on how confident we are in the answers we've pencilled in so. So, the effects of incorrect or poorly supported answers can't be encapsulated, they warp our entire strategy for solving the crossword puzzle.
The recent GSK settlement is small but important step towards scientific transparency. The current judgment applies only to GSK, but Spitzer hopes that other pharmaceutical companies will follow GSK's lead.
Many journals have already moved to safeguard the scholarly literature against various forms of bias. Mandatory disclosures of funding sources and conflicts of interests are a step in the right direction. The key journals should do even more to address publication bias, especially the corporately-mediated species. For example, journals should require all contributors to sign a declaration that they are free to publish all data resulting from their investigations according to their professional judgment. Prestigious academic journals should not publish anything from anyone who admits to publication restrictions on unfavorable results.
Here's an idea I've been toying with for a while. How about a public repository of irreproducible results? A kind of National Biomedical Data Cemetery... Here's how it might work. If a publicly funded scientist failed to get her study published, or decided not to publish her results, she could submit her data to a national archive (anonymously, if she wished). These records would be made available to scientists, historians, policy makers, and other scholars. Such an archive would be an invaluable resource. It might help answer some of the niggling questions about publication bias that plague the biomedical literature.
I'd love to hear readers' opinions on the desirability/legality/feasibility a Biomedical Data Cemetery.
[X-posted with Majikthise]
Wednesday, August 25, 2004
Eye in the Door has more
Robert Skipper has more on Dick Cheney's inconsistent stance on gay marriage at The Eye in the Door, including an excerpt from a March 2004 interview by Wolf Blitzer.
THE VICE PRESIDENT: Well, I restated my position previously. The President has made a decision, partly because of what's happening in Massachusetts and San Francisco, that the administration will support a constitutional amendment. And that's his decision to make.
[X-posted with Majikthise.]
Purity of essence
I hope our posthuman future includes genetically modified cliche-production modules.
Case in point: Nicholas Kristof confesses that genetic technology weirds him out: [NYT permalink]
Genetic tinkering gives me the willies. My concern is not so much the details of blocking myostatin, although Belgian Blue calves are so muscled that their mothers are at high risk of dying while giving birth,as with the possibility that we will irreversibly change what it is to be human. Geneticists have tried to improve apples over the last 50 years, producing larger, prettier species that just aren't as tasty or as interesting as they used to be; it would be a tragedy if we did to humans what we've done to apples.
Kristof is obviously a big thinker. He's not one to get bogged down in the technical details of safety, efficacy, equity, and affordability. Technology is boring. Ontology is sexy. It's fun to pronounce about what it is, or what it might someday be to be human. Most pundits are incapable of discussing genetic technology without lapsing into essentialist platitudes. These writers seldom think it necessary explain how or why genetic engineering might "irreversibly change what it is to be human."
An essentialist might argue that genetic engineering emperils human essence because it removes the common denominator of arbitrariness. Before, being human meant being reconciled to the genes you were born with. We were all in this together. Soon, technology may allow us to pick and choose certain attributes. I don't see how any of this impinges on what it is to be human. The beneficiaries of genetic engineering will have made their choices according to human values to further human goals. Speculations about GM changing the essence of humanity overlook the fact that most of the things that would be desirable and ethical to change are those that we already manipulate by more pedestrian means.
I think Kristof is more concerned with the details than he lets on. Consider his apple farming analogy. What he is really worried about is whether we will alter our genes wisely. This is a question about the costs and benefits of applying technology, not a question about essence. Your view of modern apple husbandry depends on what you like in an apple. Do you prize year-round availability, affordability, and worth dearth? Or do you prefer the delicate aroma and texture of varietal fruits? These are legitimate aesthetic and economic questions. Neither farmers, nor grocers, nor pundits worry about whether these alterations have undermined what it means to be an apple.
Good flip/bad flop
Cheney Stakes Out Own Position on Gay Marriage [NYT permalink.]
In a political season marked by Republican efforts to outlaw gay marriage, Vice President Dick Cheney on Tuesday offered a defense of the rights of gay Americans, declaring that "freedom means freedom for everyone" to enter "into any kind of relationship they want to."
[Cheney] spoke on the same day that a draft version of the Republican platform was distributed to convention delegates that declared, "We strongly support President Bush's call for a constitutional amendment that fully protects marriage." The draft platform added, "Attempts to redefine marriage in a single city or state could have serious consequences throughout the country, and anything less than a constitutional amendment, passed by Congress and ratified by the states, is vulnerable to being overturned by activist judges."
Monday, August 23, 2004
Swift boats for truth
Meet Swiffie, swift boat for truth.
Swiffie the Li'l Riverboat, who served under Kerry, and is in a unique position to discredit the recent SwiftVet ads claiming discrepancies in the official record of Kerry's service.
[Via Wacky Neighbor.]
This week I'm blogging from my ancestral home of Port Moody, British Columbia. So, here's a little CanCon for your delectation. If you liked that, you'll love this collection of vintage Canadian toy soldiers. [Broken link, now fixed. Leads to real Canadian toy soldiers.]
I found this site because my great uncle Martin was waxing nostalgic about a lanyard he had in World War II. I thought maybe I could find him one online. Unfortunately, even Google couldn't deliver the goods. If anyone could tell me what kind of lanyard Canadian infantrymen used to suspend their dog tags in Germany in 1945, I'd be eternally grateful. Martin has searching for a replacement for almost 50 years now.
Sunday, August 22, 2004
Bush and Kerry war records compared head-to-head
My Left Brain compares the the war records of George Bush and John Kerry. This post is the most sophisticated and informative analysis I've seen on this subject. It is a refreshing and informative antidote to the scattershot talk show commentary.
[Via Roger Ailes.]
Saturday, August 21, 2004
Jeb Bush, apostate?
"I think it's horrific that people would do that, I don't sense that is the defining element of this storm, though."--Gov. Jeb Bush on post-Charley price gouging in Florida. [SPI]
Some might argue that "price gouging" is an unreasonably pejorative label for free enterprise in its purest form. Catastrophes reduce supply and increase demand. Classical economics suggests that price gouging in the wake of natural disasters is inevitable and even desirable. High prices are said to discourage waste and non-profit hoarding and to increase the flow of goods to stricken zones. Many free market faithfuls also defend the entrepreneur's right to profiteer. They argue that owners are entitled to sell their goods to the highest bidder. The gospel of laissez faire teaches teaches that these entrepreneurs deserve whatever price their goods will fetch. On this view, it is simply wrong to interfere with the seller's right to name her price, regardless of the consequences of her business practices.
Rawls, justice, and desert have become hot topics in the blogosphere. (See Scott Paeth for a thoughtful precis of recent discussions.) Libertarian/objectivist Will Wilkinson has made Reflective Equilibrium a water cooler issue.
Rawls' method of Reflective Equilibrium (RE) can be used to reason about the ethics of price gouging. Rawls argues that we should develop our stance towards gouging (or anti-gouging laws) by scrutinizing our preexisting attitudes towards the practice and attempting to reconcile them. In this case, we feel the pull of two compelling normative claims: a) that property owners are entitled to dispose of their goods as they see fit, and, b) that people who demand exorbitant prices from desperate people act unjustly.
Our laws and public discourse reflect an some uneasy and incomplete middle ground. Florida is one of at least 20 states with anti-gouging laws. (For more details, cf the invaluable Brendan Koerner.)
As usual, Jeb Bush seems slightly unbalanced. As a free market apostle he ought to welcome the wave of free enterprise. Yet, he too recoils at the thought of greedy business owners exploiting desperate citizens. The irony isn't lost on Mark Kleiman:
I can see both sides of the argument; my point here isn't that anti-gouging laws are wrong, but that they ought to be controversial in a way they currently are not, at least among those who consider themselves principled advocates of laisser-faire.
Maybe Jed is just pandering to disgruntled electorate. Maybe he believes that the price gougers are (expendable) red-blooded entrepreneurs. Somehow I doubt that. The Governor seems sincerely appalled by the behavior of the storm profiteers. Sadly, I doubt this tension will prompt the governor to reassess his theory of justice.
[x-posted with Majikthise.]
Fair's election equation
VOTE = 55.57 + .691*GROWTH - .775*INFLATION + .837*GOODNEWS
The media hook is obvious: distinguished scholar defies conventional wisdom to predict Bush landslide. So, it's probably not surprising that Ray Fair's election equation has generated so much attention. Over the last few months Fair's predictions have been cited by such influential sources as the The New York Times, The New Yorker, MSNBC, and the National Review Online. Eugene Volokh has even commented the Fair coverage, so we know we've got a phenomenon on our hands.
Unfortunately, the press has glossed over the reasoning behind Fair's predictions. The celebrated election equation is just a linear regression. Fair plotted vote share against economic data for American presidential elections (1919-2000). His model weights the following factors: incumbency, economic growth and inflation during the election year, and "goodnews" (how many of the last 15 quarters saw growth >3.2%). The election equation is based on correlations, but Fair believes that his model captures a causal relationship between the economy and voting. He claims that his model predicts electoral outcomes because people vote to maximize their expected utility. He makes the further claim that voters make their decision based prevailing economic conditions and the assumption that they are better off under an incumbent with a reasonable economic track record.
Some question Fair's assumption that the economy will receive historically typical consideration in 2004. But even if we set aside these Humean worries, Fair's model is seriously compromised. The unreported story is that bad economic news has steadily eroded Bush's projected lead. Even so, Fair steadfastly maintains that Bush has this election in the bag (unless his model is deeply flawed). To satisfy his readers that Bush's projected advantage is not due to overly optimistic projections for Q3 2004, Fair allows readers to plug their own data into his equation. The model projects a Bush victory even for dire Q3 predictions. Why? Largely because incumbents have historically enjoyed such a big advantage over challengers.
One reason for Bush's strong standing is that he gets a substantial head start by virtue of the incumbency effect. As calculated by Fair, any member of the incumbent presidential party is presumed to derive some benefit, but none more than a Republican whose party has been in office for only a single term. Based on Fair's analysis of elections since 1916, Democrats always have a slight disadvantage, and voters tend to tire of the incumbent party the longer it has occupied the White House. [MSNBC]
Fair is predicting one of the biggest landslides in American political history, a prediction sharply at odds with polling data. The latest polls give John Kerry a slight edge in a very close race.
When asked to explain the gap between his predictions and the best measures of political opinion, Fair dismisses polls as "flaky" [NYT]. Fair can't afford to be so cavalier. His model ought to fit the preliminary data, but it doesn't. The model assumes that voters deliberate rationally and that they assign the same weight to each variable as the model does. Fair believes that people vote their economic self interest based on the assumption that an incumbent with a decent economic track record will help them.
If Fair is right, voters already have most of the information that they will use to make up their minds in 2004. They know who the incumbent is. They know about the disappointing second quarter data. They know that Bush only has two "goodnews" quarters in his entire presidency.
Today's polls must already reflect Bush's incumbent's advantage and his economic performance to date. If Fair's model is correct, Bush should already enjoy a substantial lead. The fact that he's tied or trailing is already worrisome from Fair's point of view. Moreover, if the electorate were to shift its opinions to match Fair's projections, his theory couldn't explain why. Fair claims that his model is successful because it captures the rational weighting process that voters use to choose their candidates. But if voters do stampede for Bush in the waning days of the campaign, their behavior won't conform to Fair's weighted averages. We know this because the public already knows most of what Fair says they need to know to make up their minds. So, Fair is in a double bind. If his model gives the right answer, we will know it did so for the wrong reasons.
[x-posted with Majikthise.]
Wednesday, August 18, 2004
If there's one thing that you learn by being in academia, or by being a blogger for that matter, it's to speak with authority on things you know little about. On Sept. 1st I get to put my skills to some use, participating in a roundtable discussion hosted by the Remy Bumppo Theatre Company. Their upcoming season, entitled "Chaos Theory and Other Family Gatherings," features three plays with some connection to science: Delicate Balance by Edward Albee, Arcadia by Tom Stoppard, and Humble Boy by Charlotte Jones. Each play will be commented on by an expert of some sort or another, and then we will all join in with artistic director James Bohnen to discuss connections and so forth. I'm responsible for Humble Boy, and will also give some sort of lecture when the play opens in the spring (not that you can glean any info about it from the RBTC website).
I haven't actually read the play yet -- that's a project for the plane ride home -- but I've learned some of the basics about it. It's loosely inspired by Hamlet, and features as its central character an indecisive theoretical physicist who is struggling in his personal life when he's not busy trying to unify gravity and quantum mechanics. (Well, who isn't?) I'm crossing my fingers here -- the track record of authors using science as a source of metaphor and imagery is a mixed one, at best. I'll let you know how it goes.
And now I need to hop in a train and cross the Alps. You're in Lindsay's capable hands for the duration.
Tuesday, August 17, 2004
John the Baptist and the Hermeneutics of Scientific Reporting
Being a science journalist has to be one of the most difficult jobs I can think of, requiring both common journalism skills as well as an ability to understand and judge the importance of claims in a wide variety of obscure specializations. Still -- a lot of it is very bad. Which is a shame, since so many people get most of their knowledge about contemporary science through the news.
Fortunately, there are certain strategies that can help you understand what is really going on when you read a piece of science journalism. As an example, let's consider the breaking news about the cave linked to John the Baptist that has just been found in Israel.
TZOVA, Israel (Reuters) - A British archeologist has dug up evidence linking John the Baptist to a cave used for bathing rituals in hills near Jerusalem in what he said could be one of the biggest recent finds for Christian history.Okay. For a start, these claims seem pretty grandiose. I don't know anything about archeology, and precious little about Biblical history, so for all I know this guy could be completely accurate. But you do worry a little when scientists not only make absolutely fantastic claims, but seem willing to extrapolate far beyond what they have actually found evidence for (in this case, talking about Jesus). There is pressure to make your findings sound interesting to the public, and sometimes we get overly enthusiastic, but this is definitely a warning sign.
Discovered by Gibson in 1999, excavations at the cave since then have revealed a large bathing pool as well as objects used for anointing rituals that would be quite different from those used by most Jews there nearly 2,000 years ago.Perhaps this is just me, but that last paragraph makes no sense. Are the drawings at the site, or are there drawings elsewhere that link John to the site? Why do we care that he is portrayed in a similar way to other Byzantine art? How do we know that the drawings are of John the Baptist? Most of all, do the conclusions being reported here rely on the assumption that there are no distortions that might creep into an oral record over a period of 400 years?
"Nothing like this has been found elsewhere," Gibson said. "It is the first time we have finds from the early baptismal period ... It is an amazing discovery that happens to an archeologist once in a lifetime."Ding ding ding! He's writing a book. Already has written one, in fact. So there might be some conflict of interest between appropriate scientific skepticism and the selling of the story. Also, why is the finding only being announced now? It must have taken some time to write the book -- presumably the archeological finding would have been published in a reputable journal some time back?
Any discovery of sites linked to the Bible is certain to stir controversy and its share of skepticism, but Gibson said he had carried out many tests to satisfy himself that his theory was sound. The Bible describes John performing baptisms -- including that of Jesus -- in the River Jordan, a good 25 miles east over the Judean desert.Okay, now we are told that there is actually a conflict between what we know about John and where the cave was found. And a flimsy explanation is offered. But we are supposed to be reassured, since Gibson himself has carried out many (unspecified) tests. Notice that there are no outside experts quoted in the article. Even when there are, you need to take what they say with a grain of salt, since they have typically not had a chance to review the claimed findings in any detail, and have to rely on their general expertise in the subject area. When they are completely absent, it's a bad sign.
"In addition to John the Baptist, there's a possibility that Jesus used this cave as well," said Gibson.Yes. There is also the possibility that Alexander the Great slept there, and the Loch Ness monster has visited. There are lots of possibilities. If there were any actual evidence that Jesus had been there, do you think we'd spend so much time talking about John the Baptist?
Gibson said he was sure the cave could not have been put to other uses -- as a water store or a hideout for example -- or that it was used by any other group carrying out similar types of rituals around the same time as John.What coincidence? That some non-famous person was using the cave for some good reason? Most of the people alive two thousand years ago were not celebrated figures from the Bible, and most archeological findings are not going to represent important events in the lives of famous people.
Again, I have no expertise in this actual area, and for all I know Gibson may turn out to be completely correct and his findings may go down in history as a major breakthrough. But we don't have evidence for that from this story. The journalist can always say that they are simply reporting what they have been told. But I don't really think that is the end of the journalist's job -- it's perfectly appropriate to exercise some judgement about the claims being made. Unfortunately, if you spend just a day talking to outside experts and verifying the credibility of the story, your rivals will get the story out before you, and that's the major criterion for success in the news business. So it's up to the readers to use their own judgement.
My personal experiences have been with stories about science. But something tells me that stories about politics are not that different.
Monday, August 16, 2004
What do you call a drive-through liquor store?
Switzerland is a very cosmopolitan country (despite clinging to their own currency rather than bowing before the Euro), with no fewer than four official languages (German, French, Italian, and Romansh). On the Lufthansa flight from Frankfurt to Geneva, each announcement was first made in German and then repeated in both French and English. I don't know whether the English was simply a bow towards the universal language of the world, or whether the fact that the flight was officially a code-share with United had something to do with it.
The existence of multiple official languages must create occasional headaches. Of course, in the U.S. we don't have any official language, attempts by organizations like U.S. English notwithstanding (warning: cheesy patriotic music). And English doesn't have an official governing body, so we don't have to live through nonsense like the German spelling reform. Which I think is a good thing, since like Steven Pinker I fall firmly on the descriptivist side of the descriptivist/prescriptivist debate over the nature of language, believing that rules bubble up from the bottom rather than being imposed from the top. (Although I enjoy reading David Foster Wallace defending the opposition.)
Despite our lack of central authority, the usage of American English is probably more standardized than either French or German. But we do have charming regionalisms, which have been studied in the fascinating Dialect Survey. The Dialect Survey maps will tell you, for example, that "the devil is beating his wife" is simply Southern for "sunshower," while the important dibs/shotgun distinction has no strong geographical bias. I was interested to see that my linguistic upbringing was almost perfectly standard, in that I fall into the majority category of almost every regionalism. The one noticeable exception was that I grew up calling subs "hoagies," a distinct Philadelphia/New Jersey usage. And I am shocked to learn that nearly half of the country refers to sneakers as "tennis shoes." Takes all kinds, I guess.
Also, over seven percent of Americans have no word to describe the concept of ogling. How do they make it through the day?
Saturday, August 14, 2004
Greetings from Frankfurt airport! I have nothing special to say, but it just feels especially modern and sophisticated to be able to sit in a European airport cafe and post to the same blog that I would from home. German was the language that I took in high school, but it appears to have completely fled my brain; when I try to talk to any of the airport staff, it comes out in French, and I don't even speak French. Fortunately they all speak English, as nobody is surprised to hear. Unfortunately, Germany seems to be one of those benighted countries in which the default mode for cappuccino is to have cinnamon on top.
No sleep on the flight over. All of my immediate neighbors were part of a single group, who seemed new to the concept of transatlantic travel, and thought it would be fun to chat the night away rather than grabbing a precious hour or two of sleep. What kind of group was it, you may ask? Well, they were going to Athens. For the Olympics. But not to actually watch the sporting events. No, they were going to be handing out tracts to passers-by, trying to persuade them to accept Jesus as their savior. (Chick tracts? I don't know, and feared to ask.) I alternated between reading the latest Harry Potter book (now out in paperback) and working on a paper on the Big Bang -- so I don't know if they didn't proselytize to me because they were saving their energies for Greece, or because they had given up on me without even trying.
Okay, so I did have something to say. I'm just too exhausted to say it in any sort of nuanced way.
Friday, August 13, 2004
The image of the United States in the world has, to be sure, taken a big hit over the last couple of years. Clearly drastic measures are called for. What better way to get people throughout the world to think better of us than to let them listen to some cool jazz? Something along those lines must have been going through the minds of the clever folks at the State Department and Lincoln Center, when they got together to start the Jazz Ambassadors program.
The idea is to assemble a few small groups of talented (and hopefully diplomatic) musicians, and send them on several-week tours of places that don't get much exposure to US culture. I know about it because Michael Raynor, a friend of mine who is Von Freeman's drummer, has just left for a tour with the Chicago Jazz Quartet, a group thrown together for just this purpose. They will be visiting Vietnam, Thailand, the Phillipines, Indonesia, Pakistan, and Bangladesh before returning to the City of the Broad Shoulders. Perhaps, through the wonder of swinging, improvised music, they can bring peace and prosperity to the far reaches of the earth. Or maybe they will merely entertain and stimulate some audiences of people who think of Rambo when anyone mentions the United States. Which would make the project more than worthwhile.
Meanwhile, I shall go hop on a plane, and when you next hear from me I should be in Geneva, land of international banking, accurate timepieces, and high-energy particle physics. Further reports as events warrant.
Thursday, August 12, 2004
Congratulations to Suz!
The National Science Foundation runs a Research Experience for Undergraduates (REU) program, which provides funds to universities that would like to sponsor undergrads to visit for the summer and engage in some real live research. This summer I've been advising Suz Tolwinski from Brown (see a tiny picture at my group web page), who gave a presentation this morning on what she's accomplished.
Undergraduate research experience is very valuable, but it's hard to do as a theorist, since there is so much background knowledge required before you can do original work. I've advised a few undergrads, both during the school year and during the summer, and usually ask them to learn enough general relativity and cosmology that they can at least begin to answer an original question. (Actually, I usually just say "no," but occasionally the stars align correctly and I agree to advise someone.) If all goes well, at least they will learn a lot of good physics. But teaching yourself GR over a summer, with time enough left over to work on a real problem, is undertaing a tremendous task. Suz did a great job, learning both GR and some bits of classical field theory from scratch, and then investigating whether Lorentz-violating vector fields would lead to an observable anisotropy (direction-dependent stretching) in the expansion of the universe. This is an extension of work I did with Eugene, except that Eugene's vector fields were pointing in a timelike direction, and Suz's were spacelike. Which is actually harder! So I was very impressed with the final project.
Actually, I was impressed with all of the REU presentations this morning, on topics from waves traveling through sand to numerical investigations of cellular automata. It was a tremendous joy to hear about the accomplishments of these students, especially when you remember that doing physics research is not how most undergraduates spend their summer vacations. Being an academic can be a stressful occupation, as discussed recently in posts at Pharyngula and Uncertain Principles (referencing several other academic blogs, including Making Contact, Steven Krause, Playing School, Irreverently, Just Tenured, Barely Tenured, and Bitch. Ph.D.). One of the things that Suz has been wondering about is how happy one actually is as a science professor, especially after talking to current graduate students and hearing stories of, shall we say, incomplete contentment. I'm not the most representative person to comment on the pros and cons of academia, since I've been passionately in love with the idea of being a professor ever since I understood what it meant. I mean, our job is to teach and do research; what could be better than that? There are certainly less-fun parts of the job (applying for grants, grading, committee meetings, etc), and it can undoubtedly be stressful and over-competitive. But it's too easy to get run down by these aspects and forget about the exhilarating ones. Listening to a collection of talented and enthusiastic students explain the research they've been doing over the summer is an excellent way of being reminded.
Wednesday, August 11, 2004
Extinction of less-improved forms
Tangled Bank #9 is now online over at Pharyngula. The idea behind Tangled Bank is to collect together a weekly greatest hits of science/nature posts in the blogosphere and stick them in one place for easy consumption. The greatness of the posts themselves is decided upon by their authors; if only more things in life worked that way.
Most of the TB posts are oriented toward the biological sciences; I sneaked myself in only on the basis of my dinosaur reports. Maybe they should do more physical sciences?
On Friday I head off again for a couple of weeks, and blogging abilities might be spotty. I'm spending a few days visiting friends at CERN, the particle accelerator in Geneva where the World Wide Web was born, so presumably it won't be too hard to find an internet connection (although things might be hectic). After that it's off to the European Forum Alpbach, where Bob Wald and I will be giving a series of lectures on cosmology. Alpbach seems pretty far away from everything (not even a train station), and I'm guessing it's rather isolated.
So I'm very happy to introduce another guest-blogger to keep things cooking while I'm away: Lindsay Beyerstein will be piloting Preposterous while I'm galivanting around the Alps. Lindsay is the proprietess of Majikthise, one of the most stimulating and well-written blogs out there, as you will soon discover if you haven't already.
I am hoping that my willingness to choose guest-bloggers who are more entertaining than I am will be seen as an indication that I am self-confident enough to not fear being upstaged, much like John Kerry choosing John Edwards as his running mate.
Tuesday, August 10, 2004
Daily dinosaur comics
Click the image for more. I had run across this some time ago, and was reminded of it in a post at Uncertain Principles. Consistently amusing, within even tighter self-imposed constraints than the original Law & Order series.
Save yourselves! Move to the midwest!
Another reason why living by a Great Lake is better than living by the ocean: little danger of tidal waves.
I like "They also fear southern England could be hit." And this is a British scientist, in a story reported by the London Telegraph.
But there's good news, as well: hysteria about being hit by an asteroid has somehow managed to decrease that risk from "microscopically small" to "really so miniscule that we can relax a little." Thank goodness about that.
Monday, August 09, 2004
Hubble imaging spectrograph dies
As Jennifer mentions in the comments, one of the instruments on the Hubble Space Telescope has apparently broken down: the Imaging Spectrograph, used to (obviously) take images with simultaneous spectral information, for example of black-hole candidates. This is too bad but not a complete catastrophe (unless you had time on the instrument); it had already lived past its expected lifespan, and there are still three instruments working on HST. Sure would be nice to have a servicing mission, though.
As far as I can tell, our track record of reaping long-term benefits from our support of repressive and authoritarian regimes is pretty dismal. Yet, we keep on doing it, mostly for short-sighted reasons. Saudi Arabia is the example that has been drawing increasing scrutiny.
The latest charming anecdote: three reformers (Ali al-Demaini, Matruk al-Faleh and Abd Allah al-Hamed) have been arrested for "calling for adopting a constitutional monarchy and using western terminology," among other heinous offences. These are not exactly anarchists we're talking about here -- their role model is Jordan.
I wonder what Western terminology they were using? "Radical, dude"?
Millennium Park: Franks and Beans
This weekend I had a chance to visit Chicago's latest attraction, the somewhat-misnamed Millennium Park. This is a parcel of land just north of the Art Institute, adjacent to Grant Park, that had been languishing as a railroad yard, until the city powers decided to spruce it up as part of a celebration for the year 2000. Somewhat behind schedule and substantially over budget, the project has finally been completed, and has garnered rave reviews from visitors thus far.
Easily the most talked-about component of Millennium Park is the large reflective statue by Anish Kapoor, officially named "Cloud Gate" but universally dubbed "The Bean." (Click for full-sized version.)
Now, I had actually seen a model for the park a couple of years ago, and had no doubt that this abstract beast was going to be a complete disaster. Let me publicly state that I was completely wrong; the full-sized bean is strangely compelling and irresistible. Reflecting the skyline and the sky itself with a gentle distortion, this simple shape grabs your attention and holds it with an eerie fascination.
You can also walk underneath the bean, where Kapoor has manipulated the reflections to produce interesting multiple images. Viewers can happily alternate between looking for images of themselves in the interior of the bean, and wondering at the ease with which their fellow visitors are entertained.
Photos don't really do the bean justice, but you can't help but taking many pictures when you are in its presence; I predict with confidence that within a short time this sculpture will be recognized as the most-photographed object in the world. (Note that the sculpture is actually not complete; the visible seams are to be welded to form an unbroken smooth surface.)
To be honest, the simplicity of the bean is also its limitation; it only provides perhaps fifteen minutes of contemplation before you are ready to move on to something else. Fortunately, the Art Institute is just to the south, so a pilgrimage need not be exclusively beanocentric.
The other new attractions in the park are also worth attention. An interesting, although less obviously successful, art installation is the computerized fountain designed by Barcelona artist Jaume Plensa. It consists of two rectangular towers that gently spray water in all directions, and project moving images of faces (apparently supposed to be representative citizens of Chicago). At occasional intervals the faces appear to spit water from their mouths, in a reference to more classical fountain designs.
While the fountains don't have the immediate and universal appeal of the bean, they are a big hit with kids, who can frolic around in the water to their heart's content. An obvious worry is the upkeep associated with the fountain systems -- these would be a complete disaster if they were allowed to fall into disrepair.
Before the bean captured everyone's heart, the centerpiece of the Millennium Park project was a new band shell designed by Frank Gehry. It brings to mind giant chocolate shavings on the top of an especially elaborately decorated cake (if chocolate shavings were made of stainless steel).
This photo isn't a very good view of the band shell itself, because I wanted to note a cute science fact about the trellis extending out from the shell and covering a wide section of park in which visitors can relax and listen to concerts. You will notice the speakers hanging from the trellis itself; often attempts to amplify outdoor musical performances result in acoustic nightmares. To prevent this from happening, the designers calculated the time it would take sound to reach from the stage to different points in the audience, and have built in an appropriate delay in the signal sent to the speakers so that the sound reaches the listener from both sources simultaneously. Now that is good planning.
Friday, August 06, 2004
Finally, a choice
Longtime Preposterous readers know that some time ago I endorsed Barack Obama for our open Senate seat here in Illinois. At the time, I thought the alternative would be Republican Jack Ryan, who was most famous for having been previously married to an actress. But, as we all know, Ryan had to drop out after some messiness involving Paris sex clubs (always more trouble than they are worth, take my word for it). And now it looks like charismatic talk-show host Alan Keyes might be our new Republican nominee. Like everyone else, I always took Keyes for a complete nutcase. But perhaps I was wrong. According to his own website, Alan Keyes:
Thursday, August 05, 2004
When it comes to quantum gravity and fundamental physics more generally, there is a lot we don't know, and many different approaches to making progress. A top-down kind of approach attempts to figure out what the ultimate laws are, and then see what they might have to say about reality; string theory is the obvious example. But you could also take a bottom-up or phenomenological approach, in which you try to figure out what kinds of physical effects might arise due to quantum gravity and then go look for them, even if you haven't derived them from a more complete theory. Tests of Lorentz invariance provide a good example, and the subject of my recent paper. This is the paper I mentioned writing with my (former) student Eugene; he now has a follow-up paper extending our work.
Lorentz invariance is simply the idea that there is no preferred direction in spacetime. Not only do the laws of physics not care about the direction in which you are looking (invariance under spatial rotations), it also doesn't care about the speed at which you are moving relative to other stuff in the universe (invariance under "boosts," as physicists would say). The idea is a cornerstone of relativity, and got a big boost (pun unintended, but accepted) when the Michelson-Morley experiment showed that the speed of light seemed to be the same in all reference frames -- there was no evidence for a background "aether" with respect to which you could measure your velocity. But its roots actually go back to Galileo, who first proposed that all velocities were relative; to people on the sidewalk, the road is stationary and the cars are moving, but to people in the cars, they are stationary and the road is moving, and each perspective is perfectly valid.
Actually, this violating-Lorentz-invariance stuff is not new to me. Using cosmology to test Lorentz-violating theories was the subject of my first published paper. It was a collaboration with George Field (my Ph.D. advisor) and Roman Jackiw, both very accomplished theorists in astrophysics and field theory, respectively. My role as the meek young graduate student was largely to type in the data and make plots, but that's how you get started in this business.
The theory we considered had a fixed timelike vector field without any independent dynamics, but it was coupled to electromagnetism in a specific way that violated parity as well as Lorentz symmetry. We showed that the coupling would cause a "twist" in the polarization of light coming from distant galaxies, and George knew that for certain radio galaxies you could determine what the polarization should be without any Lorentz-violating effect, allowing us to put a very tight limit. The data I typed in came from different sources, and consisted of the polarization information plus the distance (actually, the redshift) of the different galaxies. Years later, much to our surprise, this same data appeared on the front page of the New York Times. Two researchers had used our dataset but analyzed it in a different way, trying to constrain a vector pointing in a spacelike direction rather than a timelike one. The big difference is that they claimed to actually find a nonzero effect, which they announced in a press release before they made the paper available to other experts. Unfortunately they were just mistaken, as I recount in great detail here. But it's still worth thinking about; indeed, some candidates for dark energy in the universe could lead to a very similar effect, so it's worth improving the present data to put much tighter constraints (or to discover dark energy!).
What Eugene and I have done is a little different. We imagine there is a vector field through spacetime that violates Lorentz invariance (since you could, in principle, measure your speed with respect to it in an absolute sense), but we worry about its gravitational effects rather than its interactions with ordinary matter and radiation. Interestingly, we find that the vector field has no effect if there is no matter lying around, but it works to alter the strength of the gravitational field caused by matter. In other words, it changes the effective value of G, Newton's constant of gravity. This would be an unobservable effect if it just changed Newton's constant once and for all, since we have no experimental knowledge of what the constant was before the vector field messed with it. Fortunately, it changes it in different ways in different circumstances: making the effective value of Newton's constant larger in the Solar System, but smaller when we consider the expansion of the entire universe.
Thus, we have an observational constraint: measure the value of G in the Solar System, use that to predict something about cosmology, and compare with the data. The most straightforward example is actually the primordial abundance of light elements such as Helium and Lithium. These were created at an early time after the Big Bang (between one second and a couple of minutes) as the universe expanded and cooled, and the precise amount of different elements you get depends sensitively on the expansion rate of the universe, and thus on Newton's constant. We find that our vector field must be less than ten percent of the Planck scale, the fundamental unit in physics where gravity and quantum mechanics come together. The Planck scale is pretty big, so it's not a great limit, but still an interesting one.
Wednesday, August 04, 2004
Is that an expanding universe in your pocket, or are you just happy to see me?
Everyone was (justifiably) jealous sometime back when I revealed that I had received a WMAP beach ball in the mail. WMAP, the Wilkinson Microwave Anisotropy Probe, is a NASA satellite that has taken the most precise images yet of the leftover thermal radiation from the early universe. Who wouldn't want to have a beach ball with a snapshot of the whole universe on it?
Well, I can't help you with the beach ball, but here's something almost as good: a CafePress store selling all sorts of WMAP merchandise, including the boxer shorts shown at right. (Found linked from Licia Verde's home page.) There's something for everyone -- T-shirts, teddy bears, thongs, more than you would ever want, really.
Someday I will follow through on the idea of setting up a store for Preposterous Universe merchandise. (In the meantime, just go buy my book!) Maybe I'll stick with coffee cups, though.
Tuesday, August 03, 2004
Dinosaur report II
Continuing the story from yesterday, let's say you're an enthusiastic amateur about to go out in the field (led by one of the world's experts) and dig up some dinosaur fossils. Your first question would of course be: what do I wear? You'll want good hiking boots, sturdy but not too heavy. It's beastly hot, so you'll be tempted to wear shorts, but don't; you'll be tromping through cactus and sagebrush, and then spending hours kneeling on rocks and dirt, so jeans are definitely called for. Hat and sunglasses are mandatory. Some of us wore lightweight long-sleeved shirts, although I did fine with T-shirts and heavy doses of sunscreen; despite the relentless Wyoming sun, I managed to keep my healthy pale complexion largely intact.
Besides clothes, the only necessary items we were personally responsible for were our water canteens. Bug spray is a good idea, and cameras or binoculars are useful, but not required. The serious equipment was provided for us by the Project Exploration folks: GPS units, walkie-talkies, brushes, awls, hammers, gloves, shovels, pickaxe, hardener, glue, tinfoil, burlap, plaster, measuring tape. Nothing very high-tech, other than the GPS. The physicist in me was sure that there must be some X-ray-like technique to probe into the soil to distinguish fossils from the surrounding rock; but nobody knows of any good way to do it, and I didn't have any useful ideas. (I'm a cosmologist, okay?)
Suitably equipped, we head out to the site. Let me just mention that none of the skills one develops by spending one's days doing theoretical physics and one's evenings at jazz clubs really come in handy out in the field. The work involves serious physical labor and tremendous patience; the good news is that, although it requires years of training and practice to be really good at it, essentially anyone can be productive after a short tutorial. It helps that Paul seems to have an endless (or at least substantial) supply of patience and confidence in his motley crew of city folks; in his shoes, I would be scared to death of what these klutzes were likely to do to my fossils, and would simply ask them to watch from a respectful distance while I did the work myself.
Our group was about fifteen people, of whom two (Paul and Bob Masek, a fossil preparator at the University of Chicago) really knew what they were doing. Of the rest of us, about half had been along the year before, and the newcomers would occasionally (in their naivete) look to us for guidance. We took two vans from the ranch where we were staying out to the site, or at least as close to the site as we could get in the vans. From there we have to lug the aforementioned equipment to the actual fossils, at which point the excitement starts.
The main fossil Paul and his students had found was a vertebra from the tail of what is likely to be a Camarasaurus, a large sauropod common in the Jurassic. (Yes I know the link says that Camarasaurus was "much smaller" than other sauropods, but when you're 60 feet long and weigh 20 tons, you're large in my book.) Sauropods are the hulking big four-legged herbivorous dinosaurs with long necks, like Brachiosaurus and Diplodocus; other major categories are the mostly-carnivorous theropods such as raptors and T. Rex, and ornithischians or bird-hipped dinosaurs, including most of the funky armor-plated species like Triceratops and Ankylosaurus. Just to add an element of confusion, actual birds evolved from the lizard-hipped theropods, not from the bird-hipped ornithischians.
What you typically find, of course, is a single bone sticking out of the rock. In this case, Paul had found a vertebra from the tail. The question then is, if you follow the trail into the rock, do you just find the tip of the tail, or most of the dinosaur? In other words, in which direction is the tail pointing? You just have to dig and find out.
This is where the patience and determination come in. You basically poke gingerly at the area around the fossil with an awl, then remove the dirt and stones with a brush. (Try not to use your fingers, or let the stones fall onto the fossil; a brush is gentlest.) The awl and brush are your most common tools. From the variations in texture and color, you should be able to tell the bone from the surrounding rock if you are careful, although sometimes it's tricky even for the experts. (The experts, by the way, refer to the rock in which the fossil is embedded as "matrix," thus adding to the science-fictiony feel of the whole enterprise.) At first you have to move extremely carefully and tentatively, as you don't know where the rest of the bones are. Every time you uncover a little bit of bone, you pour hardener over it to help protect it from being scratched or shattered. As often as not, the bones are not "articulated" -- arrayed in a nice dinosaur shape -- but rather are jumbled together. But after you make a little bit of progress, you can begin to get a feeling for the way in which the skeleton is arrayed in the rock. At that point, you might decide that the three feet of rock above your fossil can be removed more rapidly than awls and brushes allow; that's where the pickaxe and shovels come in, or even jackhammers or heavy machinery in extreme cases.
Here's a picture of Paul hugging the part of the tail we have uncovered. He's feeling protective because we had very good news: the fossil seems to be pretty much articulated, and even better the vertebrae are growing as we move into the rock! Which means there is an excellent chance of finding a substantial portion of Camarasaurus skeleton lying in there, undisturbed for the last 150 million years.
Our rate of progress wasn't nearly enough to imagine actually excavating the thing; the picture here basically shows the end result of a day and a half of work. Further trips will be required before the entire fossil can be shipped to Chicago. To protect what we have uncovered, we first cover the bones with tinfoil, then with strips of burlap dipped in plaster. The plaster will not only protect the bones once we cover them with dirt again, it also will make it much easier to eventually bring the fossil home. In fact you don't nearly dig away all the rock from the bone; you intentionally leave an inch or two of matrix surrounding the bottom half of bones, dig out from the bottom, and then plaster around the entire collection, which gets shipped back to the lab. (A ton or two of shipped materials is common.) There a real expert, working in decent conditions (presumably involving air-conditioning), can remove the rest of the matrix. Then you take appropriate pictures and measurements, and possibly think about mounting the specimen for display. If (as Paul often does) you went to Niger or Mongolia or Argentina to collect the fossils in the first place, the original country will typically want it back; you get the science out of it, and it ultimately returns home. For our Wyoming fossils, we hope to build up a collection at the University; the previous collection was short-sightedly given away.
This is the second year I've gone on one of these trips with PE. The first year was great fun but I was exhausted by the end; this year I wanted to stay out there and keep digging. It's an exhilarating experience, and utterly different from being a theoretical physicist. On the other hand, dinosaurs and cosmology are two topics that readily engage the public imagination, and the folks at PE hope to extend their reach into other areas of science, so I hope I can be some help. At the end of a long day in the field I gave an informal lecture on black holes -- amazingly, despite myriad other distractions and every reason to be tired (the lecture began at 9:30 p.m.), everyone on the expedition attended and asked great questions about the curvature of spacetime. Just one more reminder, as if any were needed, that most people are intrinsically fascinated by science, and it's our duty to do a better job of sharing the excitement that professional scientists get to feel all the time.