For those of you interested in the attempt by Kolb, Matarrese, Notari, and Riotto to do away with dark energy, some enterprising young cosmologists (not me, I’m too old to move that quickly) have cranked through the equations and come out defending the conventional wisdom. Three papers in particular seem interesting:

• Éanna Flanagan, hep-th/0503202
  “Can superhorizon perturbations drive the acceleration of the Universe?”
• Christopher Hirata and Uros Seljak, astro-ph/0503582
  “Can superhorizon cosmological perturbations explain the acceleration of the universe?”
• Ghazal Geshnizjani, Daniel Chung, and Niayesh Afshordi, astro-ph/0503553
  “Do large-scale inhomogeneities explain away dark energy?”

I think the general lesson seems basically in line with my earlier suspicions. (Not that I’m claiming any sort of priority; the people who do the work should get the credit.) I mentioned the idea of the vacuole models, which give you exact solutions for large-scale perturbations without any spatial gradients. In that case you recover precisely the ordinary Friedmann equation governing cosmological evolution, just with a set of cosmological parameters that differ from the background values. Of course this isn’t the end of the story, because in general perturbations will have spatial gradients, even if they are expected to be small for very long-wavelength modes. If they’re not small, they should probably show up in other ways — as spatial curvature, or as large-scale anisotropies.

The new papers seem to demonstrate that this is indeed the case. (See also comments by Jacques and Lubošš.) You can use a GR trick (the Raychaudhuri equation) to define what is basically the “locally measured Hubble constant and deceleration parameter,” and relate them to the locally measured energy density and pressure, as well as the “shear” and “vorticity” of the fluid filling the universe. The important thing, of course, is that everything is defined at each tiny region of spacetime, without appealing to what is happening far away. For a perfectly homogeneous and isotropic universe, the shear and vorticity vanish, and you recover the ordinary Friedmann equation (that’s the lesson of the vacuole models). Perturbations with spatial gradients will generically induce both shear (stretching) and vorticity (twisting) of the fluid, and these can indeed lead to deviations from the Friedmann relation. But the effect of shear is always to make the universe decelerate even faster, not to make it accelerate. Vorticity can lead to acceleration, but it is usually small; indeed (as mentioned by Hirata and Seljak), in the KMNR set-up the vorticity is zero all along. So there can’t be any acceleration. In fact Hirata and Seljak claim to have found exactly where the higher-order perturbative analysis of KMNR went astray; I haven’t checked it myself, but they’re most likely right.

You will have noticed, of course, that there weren’t very many days in between the appearance of the original paper and the appearance of various refutations. I can imagine what these folks all went through, working diligently through the weekend. I did that myself once, when a misleading paper (much much worse than KMNR) was getting a lot of attention and needed to be set straight, but I’m glad it’s not my standard operating procedure.

What would be really nice, even if the ultimate consensus settles down to a judgment that KMNR weren’t right, is if people understood that this is the way science works. Individual papers may be right or wrong; but they are put out there for the community to debate about, different critiques are put forward, and eventually the truth comes out. Everyone is after the same thing, trying to figure out how the universe works. Something our creationist friends will never quite appreciate.

This Thursday I’ll be giving the physics colloquium here at UofC, on “Why is the Universe Accelerating?” Not that I know the answer, but I’ll be running through some of the possibilities. Talk at 4:15, cookies upstairs at 3:45; anyone in the area is welcome to drop by.

This announcement brought to you as part of the proud blogospherical tradition of shameless self-promotion. (In spite of which, the outside world manages to pretend that substantive liberal bloggers don’t exist. What do we have to do?)

Scientists, even more than most people, like to believe that appearance is irrelevant; it’s the substance of a person’s work that counts. Of course this is rubbish. Substance does count, but so does presentation. This maxim holds for everything from how you write papers (where a clear and honest presentation can make your paper much more influential than it would be if it were confusing) to how you dress from day to day. Whatever we might want to pretend, people will judge you by how you look. Of course, this truism is complicated by the fact that different people will judge you completely differently, but they’ll be judging you nonetheless.

As with many things about being a scientist, it’s significantly more problematic for women. Here is one woman’s take on the issue; this is an extract from an essay by Heidi Newberg, a physicist at RPI (and one of the few scientists you’ll find who’ve appeared in Glamour).

Women know that the way we dress has a big effect on others’ first impression of us, and there are many pitfalls involved with dressing to give a lecture. The most serious wardrobe mistake that can be made by a young woman giving a professional talk is to wear clothing that is designed to make men think about sex. While you might get away with plunging necklines, bare midriffs, low-cut pants, shirts without sleeves, mini-skirts, spiked heels, and overly dangly jewelry in other contexts, even in the workplace, this clothing is far too distracting for a presentation in which you are already the focus of attention. Wearing suggestive clothing is guaranteed to focus your audience on various parts of your anatomy, rather than listening to the message you are trying to communicate. This is confusing to young women, since women are routinely expected to wear such things when they dress up for a “formal occasion.” When men dress up for work, they wear a suit. When men dress up for romance, they wear a suit. Women must make a distinction here between appropriate professional clothing, which can look feminine and pretty but not sexy, and appropriate dating-wear, which is supposed to look sexy if you want it to work. I have been at talks in which a young woman has worn clothing that is so distracting that even I have had some difficulty paying attention to what she was saying – and of course when she was finished there was not a single question from the audience.

I think there is a lot of truth there, although I wouldn’t be as directly prescriptive as Heidi. The clear point, applicable to persons of any gender, is that, if you are wondering whether people judge you on the basis of how you look, the answer is an unambiguous “yes.” But it’s up to you to decide what to do with that fact. Maybe you want to be sexy, or maybe you just want to blend into the woodwork; but there is no simple neutral place to stand at which no judgments are being made of you. What do you want those judgments to be? Do you care?

There is a range of complex possibilities on both sides (you and whoever is looking at you). If you put some effort into your clothes, some people may judge you to be frivolous, while others will treat you with greater respect. Academics in general, scientists in particular, often implicitly attach a kind of moral superiority to nondescript clothing. If you look like you actually put some kind of an effort into how you look, you are automatically suspect. Especially if you are female, some of your colleagues will not take you as seriously if you are perceived as stylish, not to mention sexy. (For many people, one of the attractive features about science is that it can serve as an escape from all the terribly messy and ambiguous features of human interactions, and if you remind them of these things they can become insecure and defensive. Or jealous. Or intimidated.) At the same time, others might tend to take you more seriously, for better or for worse — they might perceive you as just a little bit more with-it and competent than your slovenly colleagues. The only certain mistake is to think that it doesn’t matter at all.

In a similar discussion, profgrrrrl concludes that “the most important thing is to be yourself.” After all, just because someone is judging you on the basis of how you dress, doesn’t mean you have to care. Only by flouting the various unwritten rules that surround us can we ever hope to change them. Whether that’s important to you is for only you to decide.

Sometimes the truth just slips out. (Via atrios.)

“We’ve been attacked by the intelligent, educated segment of the culture.”

That would be Patror Ray Mummert, who wants to put Intelligent Design creationism in the schools of Dover, PA. Let’s hope that segment keeps attacking.

I will go one tiny step further than Ogged and claim that it actually is funny, and perhaps even ironic: China’s Human Rights Report on the U.S.

And of course, because this is the internet, the obvious cannot be repeated clearly enough: yes, the United States has a much better record on human rights than China does, or indeed than many parts of the world. And the Chinese report is not exactly a paragon of objective analysis. Doesn’t mean we’re perfect, and certainly no reason to be happy about our own situation. Any American who is not angry and embarrassed at the conditions of African-Americans in this country is just not paying attention.

Another great American holiday is upon us: the Final Four. In which the flower of our nation’s youth, in the form of the best men’s college basketball teams in the land, engage in fierce combat for hoops supremacy.

The NCAA men’s basketball tournament is easily one of the most entertaining sports events we have, far surpassing the overhyped Super Bowl for actual excitement. The one-and-done format with sixty-five teams leads to thrilling games, especially because on any given night some plucky underdogs can get it together to topple a heavily favored basketball power. Except, of course, when you have to play seven-on-five, because the referees are blantantly against you. Such an episode occured on Friday, when the valiant Wildcats of Villanova were completely robbed in their upset bid against haughty North Carolina, when the referee hallucinated a traveling violation against Allan Ray in the final seconds. The Tar Heels will go on to play Michigan State on Saturday.

The other game will feature Louisville against the University of Illinois. The latter is the state university of my adoptive home, so I should be rooting for them. But I won’t. The reason why is a long-standing embarassment that the university refuses to abandon: the tradition of Chief Illiniwek dancing around at halftime.

As you might expect, there are those who take offense at some white college student in face paint and fake feathers pretending to be a Native American chieftain (who never really existed) in order to fire up the fans at a basketball game. There are others who smirk at this excess of political correctness, and will argue with a straight face that the Chief is actually honoring the strength and determination of the native tribes of Illinois.

Except, here’s the funny thing. It’s kind of hard to argue that the Chief’s dance is in honor of Native Americans, if you look at the history of the thing. You see, the Chief’s halftime show dates back to 1927, a time when the Civilization Act of 1819 was still law. You remember the Civilization Act, don’t you? Among other things, it made it illegal for any actual Native Americans to perform their own tribal dances, since that amounted to a practice of their religion, which was banned. (Thanks to Philip Phillips for telling me about some of the history.) So, it’s hard to construe the dancing white guy in face paint as anything other than an offensive caricature.

Everyone knows this; the faculty and the student goverment of the university have voted resoundingly to drop the Chief as their mascot. Not to mention Native American groups, of course. These bodies, unfortunately, are not the ones of primary importance to the university trustees; and the alumni (who donate money) love the Chief. And Native Americans don’t have nearly the visibility or clout that other groups have; it’s easy enough to imagine the uproar if various other racial stereotypes were used as sporting mascots.

Who knows, maybe the heightened publicity from the Final Four will finally force Illinois to do something about the Chief. That was Larry Summers’ secret plan to get people talking about women in science, wasn’t it?

John Holbo shares a quote from Thomas Mann’s Felix Krull, Confidence Man, about Felix’s days as a pimp. My favorite part of the book was the account of Felix getting an impromptu lesson about cosmology.

. . . Meanwhile, Being celebrated its tumultuous festival in the measureless spaces that were its handiwork and in which it created distances congealed in icy emptiness. And he spoke of the gigantic setting of this festival, the universe, this mortal child of eternal Nothingness, filled with countless material bodies, meteors, moons, comets, nebulas, unnumbered millions of stars that swayed one another, were ordered by the effect of their gravitational fields into groups, clouds, galaxies, and super-systems of galaxies, each with enormous numbers of flaming suns, wheeling planets, masses of attenuated gas, and cold rubbish heaps of ice, stone, and cosmic dust . . .

While the Earth wheeled around its sun, so I was privileged to hear, that earth and its moon wheeled around each other, and at the same time our whole local star system moved, and at no mean pace, within the framework of a vaster but still very local star group. This gravitating system in turn wheeled with almost vulgar velocity within the Milky Way; the latter, moreover, our Milky Way, was traveling with unimaginable rapidity in respect to its far-away sisters, and they, the most distant existing complexes, were, in addition to all their other velocities, flying away from one another, at a rate that would make an exploding shell seem motionless — flying away in all directions into Nothingness, thereby in their headlong career projecting into it space and time.

This interdependent whirling and circling, this convolution of gases into heavenly bodies, this burning, flaming, freezing, exploding, pulverizing, this plunging and speeding, bred out of Nothingness and awaking Nothingness — which would perhaps have preferred to remain asleep and was waiting to fall asleep again — all this was Being, known also as Nature, and everywhere in everything it was one.

Published in 1955, the year Mann died. He didn’t know about dark matter and dark energy, but that’s okay.

Today’s Astronomy Picture of the Day is one of my favorite images — a composite view of the Crab Nebula, created by combining images from the Hubble Space Telescope and the Chandra X-Ray Observatory.

The real nebula wouldn’t look precisely like this, unless you have X-ray vision. (When I was growing up, pictures of the Crab Nebula looked like this. And we thought it was cool when they started to look like this. Kids today are so spoiled.) The blue part of the image comes from the X-rays observed by Chandra, while the red part is the optical light measured by HST; you can easily make out a disk, several light-years across, as well as a jet being emitted perpendicular to the disk. The energy driving the emission comes from a pulsar at the center of the disk. The pulsar is a rapidly rotating neutron star, the remnant of a supernova explosion observed here on Earth in 1054. Interestingly, the event was recorded by astronomers in China and also by Native Americans, but not by any European or Arab astronomers.

Don’t miss the movies of ripples propagating through the jet and disk.

On Sunday I gave the Literary Lecture for the performance of Charlotte Jones’ play Humble Boy at Remy Bumppo Theatre Company. The acting and presentation are great, it’s well worth seeing if you’re in the area. One of the many relatively small-scale companies that make Chicago such a fantastic theater town.

My job was to chat a little about the science background of the play. The protagonist, Felix, is a theoretical physicist at Cambridge, trying to use string theory to unify gravity and quantum mechanics. (The author was inspired by hearing an interview with Brian Greene.) Felix is presented as rumpled, stuttering, socially awkward, tending to appeal to Heisenberg’s Uncertainty Principle in difficult situations — pretty much your typical physicist. I talked a little about the use of scientific concepts as fertile source material for metaphors; in this case, the irreconcilable differences between gravitation and quantum mechanics are presented as analogous to the irreconcilable differences between Felix’s mother and father.

Felix: It’s like my mother was the big force — gently warping everything around her. And my father was the little force, fizzing away quietly on a microscopic level. But I can’t bring them together. I mean, I know the geography of it. It was outside the exam halls of the school of B-biology, London University. My father had just finished his Finals and he walked out and my mother was just p-passing. She’d p-paused to light a cigarette. She was on her way to sign up to a modeling agency. He went up to her and asked her if she’d dropped from the sky. She never got to the agency.

Rosie: That doesn’t sound so extreme.

Felix: But that’s not the physics! The physics of what attracted them and what kept them together.

I don’t think it’s a coincidence that the two forces came together outside the biology building. When I gave my talk at the Santa Barbara conference, I noticed that this was a consistent theme: writers seem to enjoy hinting that physicists would have an easier time unifying the forces of nature if only they would get out and have more sex. From the audience, Steve Girvin chimed in with “Wouldn’t hurt to try.”

Look, I’m as big a fan of the rule of law as the next guy. So I sympathize when people get upset because the religious right wants to toss the law out the window when it appeals to them; for a not-notoriously-liberal example see Andrew Sullivan (via uggabugga).

But, let’s be honest. Imagine that something I thought was terribly immoral was happening, in full accordance with the rule of law. Laws banning gay marriage, for example. Then I would work as hard as I could to get the laws changed. As Will Baude points out, that’s basically what DeLay and his cronies are trying to do in the Terri Schiavo case; they’re working fully within our constitutional machinery, trying to alter the laws to get the outcome they desire. (Of course, they’re doing it for ghoulish political reasons, not moral ones. And they’re not doing a very good job, passing legislation that is blatantly unconstitutional, ignoring separation of powers, and so forth. But because these are such shoddy and desperate measures, they will ultimately fail; that’s the way the system works. Nobody is manning the ramparts and ruling by force.)

Put another way: let’s imagine that an actually qualified doctor (and no, random Nobel Prize “nominations” don’t count) invented a miracle cure that could truly restore Schiavo to her pre-heart-attack state, with full mental faculties. Then I would be all in favor of keeping her alive until the cure could be tried, no matter what Michael Schiavo wanted to do, or was allowed to do by the law. And toward that end, if I were a legislator, I’d be trying everything I could think up to keep her alive.

So the crux of the matter is really that there is no such miracle cure. Terri Schiavo, the person, is gone. Her cerebral cortex has been destroyed. There is no possible way for her to be restored. It’s really an appreciation of this fact about how reality works, rather than an abstract respect for the rule of law, that separates the different sides of this issue. Those who think that Terri Schiavo’s feeding tube should be removed, in accordance with her own wishes and those of her legal guardian, understand the blunt fact about her state, namely that she is for all important purposes dead. Those who think there is a moral imperative to keep the tube in are under the misimpression that there is still a functioning person there, and that letting her die would be murder.

Those people are wrong. Over at Shakespeare’s Sister there is an interesting discussion of how secular and religious liberals can relate to each other. I think that to many of us secular types, we can easily get along with religious liberals on almost any issue; but there will always be an underlying difference, because (to us) they are getting wrong some basic features about how the universe works. Most religious liberals are not in favor of dramatic intervention in the Schiavo case, but it wouldn’t be intellectually inconsistent for them to be — perhaps God will somehow work a miraculous cure. An acceptance of the fact that the laws of nature really are laws, and that the universe isn’t going to put them aside for occasional interventions in our personal interests, sometimes does affect how we live our everyday lives.

Update: For discussion of what it means to be lacking higher-brain functions, read Chris at Mixing Memory.