Miscellany

It looks like we may have seen the first moments of a black hole being born. This image (from Joshua Bloom’s web page) shows the optical counterpart of a new gamma-ray burst discovered by the Swift satellite. It seems likely that this event has resulted from the coalescence of two neutron stars. As the neutron stars spiral together, the smaller one is ripped apart by tidal forces, spreading into a disk of material. Some of the material accretes on the remaining neutron star, which reaches the point of no return and explodes, creating a black hole. Part of the matter outside the black hole is violently ejected, crashing into the surrounding interstellar medium, producing the flash of gamma-rays detected by Swift.

I won’t go into too many details about the story, since Steinn Sigurðsson knows this stuff much better than I do, and has explained what is happening in a series of great posts (one, two, three), from which I’ve stolen everything I’m writing here (and apologies in advance for what I mess up). Gamma-ray bursts are ultra-high energy events at cosmological distances (i.e., well outside our galaxy) that have fascinated astrophysicists for years now. The crucial point is that there are two types of bursts, long-duration (a few seconds) and short-duration (hundredths of seconds). The long-duration bursts are thought to arise from especially violent supernova explosions, and are typically found in galaxies undergoing copious star formation. The short-duration ones are likely to come from the coalescence of compact objects like neutron stars or black holes. This leads to a couple of expectations: close binary systems of compact objects can take a very long time to coalesce, so there’s no reason to find them near star-forming regions (all the stars having formed long ago). Also, the closeness of the binary often arises through close gravitational interactions with other stars, which can serve to give the binary a serious kick, so that it zooms right out of the host galaxy.

However, until now astronomers had never been able to pinpoint an optical counterpart to a short-period burst. (It’s hard to determine the direction from which gamma rays are coming. Swift uses a multi-stage technique, in which it first detects the gammas and then zooms in with X-ray and optical telescopes.) The image above shows the optical counterpart of this particular burst, GRB 050509b. It is short-duration, and appears to be lurking on the outskirts of a giant elliptical galaxy. Such galaxies are no longer forming stars, and the fact that the object is outside the galaxy proper (by perhaps 35000 parsecs) makes it fit nicely with the coalescing-neutron-star model. So those few glowing pixels are perhaps the baby photos of a new black hole. Amazing what stories astronomers can spin from such sparse data.

Update: In the comments, Matt points out that the purported optical counterpart doesn’t seem to be varying, which a real gamma-ray burst afterglow certainly would be. But as Steinn says, the X-ray counterpart is definitely there.

Jennie Chen and I have written a short essay for the Gravity Research Foundation Essay Competition. You can find it at gr-qc/0505037; it’s basically a distillation of some of the philosophical parts of our longer paper on the arrow of time. Nobody claims to have a really clear picture of the onset of inflation, but two possibilities are invoked most frequently: either “chaotic” initial conditions (a la Linde), or creation of the universe from nothing. We critique the former (following Penrose) on the basis that an appropriate proto-inflationary region is fantastically unlikely to occur randomly, much more unlikely even than the spontaneous appearance of our universe in its current state. And we critique the latter by noting that it violates time symmetry in a completely ad hoc fashion — why impose certain boundary conditions at early times but not at late times? Our solution to the conundrum is to imagine a nearly-empty de Sitter state that forms the “backbone” of the universe, off of which new inflationary regions are occasionally generated via thermal fluctuations.

The Gravity Research Foundation is a funny institution, originally founded by Roger Babson (who also founded Babson College) in order to promote research into neutralizing the effects of gravity. That’s hard to do (impossible, if what we think we know about gravity is anything close to correct), and the Foundation was originally home to quite a few cranky ideas. But more recently it has become more respectable, and nowadays seems to not do much other than sponsor these essay competitions, which feature a lot of very interesting papers by respectable people. My one previous time entering (as a grad student), I got an honorable mention, which is not very hard. This time I’m hoping for some big bucks.

And if you’re not overly fond of my philosophizing, try out the Beatles’. “McCartney elaborates Frege’s sense/reference distinction.” (Via Brian Leiter.)

Greetings from Geneva, world center of banking, watches, and high-energy physics. (Three fields of endeavor which, not coincidentally, each place a premium on exquisite precision.) I’m at CERN for the week, giving a set of academic lectures on “Cosmology for Particle Physicists.” (Wow, I just gave the first lecture a couple of hours ago, and the video is already up! Welcome to Switzerland.) Here are the slides as html and a 1.2M pdf file. Nothing you haven’t seen before, in the likely event that you’ve been reading all of my talks as I put them on the web.

Four more lectures to come, slightly more detailed and technical than the introductory gee-whiz first lecture: 1. Dark matter and dark energy; 2. Thermodynamics in the early universe; 3. Perturbations and large-scale structure; 4. Inflation and beyond. Also unlike the first lecture, these will be on the blackboard instead of from some pretty computer presentation. Because I’m hard core, baby.

If I weren’t tired from jet lag and facing four more lectures to write, I’d regale you with witty anecdotes from the plane trip here. Like, how I couldn’t get past level 18 of the Caveman video game that Swissair provides to keep you from getting any sleep at all during the flight. Those damn red mammoths kept catching me.

We’re in the midst of the University of Chicago’s famed Scav Hunt, in which teams of energetic, creative, and sleep-deprived undergraduates scour the universe for all sorts of unusual objects. (The link is correct, trust me.) This year the hunt is being blogged by Connor Cyone, and the list of items can be found here (pdf). And yes, as Will Baude mentions, I do make an appearance in item 48: “Retrieve information from a black hole. Must be Sean Carroll certified. [4 points]” Consequently, I have been asked by three different teams to certify that they have indeed extracted information from a black hole, just like Hawking says we can. Accommodating soul that I am, I readily signed my name to various pieces of paper that can now be used to discredit me in the future. All for a good cause.

No more teams are likely to find me, as I am off to Geneva to spend the week at CERN giving lectures on cosmology. Do they have the Internets in Europe? Perhaps I will check in.

So, I think we set a record for visitors to Preposterous yesterday. Mark also noticed that even his blog got a lot more visitors than usual. From this we derive an obvious lesson: if you want to generate traffic, you should write about me. (Not “yourself,” you understand — you should write about me, Sean.)

Seriously, I am overwhelmed by the outpouring of supportive comments. They mean a lot to me. But I do want to clarify one point. When I mentioned that blogging will be a low priority, nobody should read that as “while I drink heavily and wallow in self-pity.” (Self-pity will not be involved.) Rather, it’s “since I don’t have much time while I scramble to get some other things done.” Perhaps I am simply in an early, denial-based phase, but at the moment I am in no danger at all of questioning myself. I am questioning the judgment of some people, but not of myself. Hopefully I will soon find time to write the posts I have in mind on wormholes, amateurs, string theory, and co-evolutionary learning. (Those are separate posts, not one big one — although that would be fun.)

In the meantime, I understand there are other blogs out there. All the ones on the blogroll are written by witty and charismatic thinkers, I encourage you to visit. (To pick two at not-quite-random, Shakespeare’s Sister and Ezra Klein are a couple I should be linking to much more often.) And don’t forget the “next blog” button in the top right corner, which is a source of constant delight. Today I discovered Sharon Spotbottom, which has some interesting and provocative cartoons. But it will be hard to beat my all-time favorite, the Bean Bag Blog.

The bad news is that I’ve been denied tenure at Chicago. It came as a complete surprise, I hadn’t anticipated any problems at all. But apparently there are a few of our faculty who don’t think much of my research. A stylistic clash, I imagine. And a handful of dissenters is all it takes to derail a tenure case. I don’t think there are many people in the outside world who believe that the University of Chicago is better off without me than with me, but there seems to be an anomalously high concentration of them among my own colleagues.

So now I am on the job market again. Which is sad, both because of the intrinsically demoralizing nature of the job market, and because I cannot tell you how much I love this city and the friends I have made here. It truly feels like home to me. But I’m hopeful of getting a position at some other great place and flourishing there — doing well is the best revenge.

In the meantime, though, blogging will likely be a low priority. I’m not going to stop, but my former ambition to put something up every day (no matter how lame) is going to be set aside as I concentrate on other things.

Further updates as events warrant.

You only ever need one time traveler convention. Because, of course, future time travelers can find out about it, and then come back in time to attend. The trick is publicity. So I am hereby doing my part, secure in the knowledge that Preposterous Universe will last for millennia, at least in archive form.

(Okay, I have to admit that this is somewhat bogus. A real time machine, i.e. a closed timelike path through spacetime, would only ever be able to take you back to the moment when it was originally created, not into the pre-existing past. So the convention will only work if someone has already built a time machine. But who knows?)

A while back Scott Hughes pointed me to the web page of the Alternative Cosmology Group. (Scott, what did I ever do to you?) These are folks who don’t really believe in the Big Bang model. The Big Bang is simply the idea that we live in a universe which is nearly homogeneous and isotropic, and has been expanding from a hot, dense state for the last several billion years. Evidence for this model is overwhelming, starting with the fundamental successes of the Hubble Law (distance proportional to velocity for nearby galaxies), the existence of the cosmic microwave background radiation (a relic from the early hot state), and the primordial abundance of light elements (a signature of nucleosynthesis when the universe was about a minute old). More recently, specific models within the Big Bang framework have scored fantastic empirical successes at explaining anisotropies in the microwave background, the characteristics of large-scale structures, the age of the universe, and so on. And patient experts continue to slap down various proposed alternatives. Still, there are doubters. Remind you of any other famously successful scientific theories?

It’s fun to go through the introductory paragraph of the Alternative Cosmology Group web site, searching for true statements. Fun, but not especially rewarding.

The Alternative Cosmology Group (ACG) was initiated with the Open Letter on Cosmology written to the scientific community and published in New Scientist, May 22, 2004.

Hey, that one’s true! The ACG was initiated with that letter. As far as I know, anyway. (It’s all downhill from here.)

The letter points to the fundamental problems of the Big Bang theory, and to the unjustified limiting of cosmological funding to work within the Big Bang framework.

No, it doesn’t, since the problems are not fundamental, and the limiting is perfectly justified. We’re short of funding as it is; why spend money on theories that have been disproven?

The epicyclic character of the theory, piling ad-hoc hypothesis upon hypothesis, its incompleteness and the appearance of a singularity in the big bang universe beginning require consideration of alternatives.

No, they don’t. Various hypotheses may or may not be ad-hoc, but they are simply required to fit the data. We should certainly be looking for ways to go beyond the currently favored version of the Big Bang model by reducing the number of hypotheses, and tying up some of the loose ends, but any such theory will simply be an improved version of the model. You won’t replace the fact that the universe is expanding from an initial hot, dense state.

This has become particularly necessary with the increasing number of observations that contradict the theory’s predictions.

No, it hasn’t, since there are no such observations.

Big Bang cosmology has been in a crisis since the early 90’s when the Cold Dark Matter model began to fail.

No, it hasn’t. The most restrictive possible version of the “Cold Dark Matter Model,” in which there was a critical density of matter particles, was indeed in trouble by the early 90’s. Those troubles were resolved in 1998 when it was discovered that the universe is accelerating, implying the existence of dark energy. The “Standard CDM” model was swiftly replaced by the “Lambda-CDM” model (Lambda standing for the cosmological constant), and problems with structure formation and the age of the universe were resolved in one fell swoop. The Big Bang model itself, of course, was never in trouble at all. (A persistent error on the part of critics is to confuse particular scenarios within the Big Bang framework with the framework itself.)

Fifteen years later, this crisis has worsened, despite the addition of dark energy.

No, it hasn’t. To the extent that it ever existed, it has gone away. Dark energy, like it or not, keeps being verified by new and independent measurements.

Observations fail to show the dramatic differences between the high-redshift and local universe required by the Big Bang theory.

No, they don’t. This is obviously false. What are they thinking?

We still find normal galaxies, heavy elements, strings and clusters of galaxies at the further and further shifting outskirts of the observable universe.

No, we don’t. Of course, it is hard to make precise measurements of ultra-distant objects, but to the extent that we can, they look different than nearby objects. Galaxies look different, elemental abundances look different, the density of various objects looks different, everything you would expect in an evolving universe.

The anisotropy of the cosmic background radiation, the existence of very large-scale structures, the cosmic anisotropy to electromagnetic wave propagation are among many observations that contradict Big Bang expectations.

No, they aren’t. The first of these two phenomena are manifestly consistent with the Big Bang, and the third one doesn’t exist.

At the same time, non-Big Bang alternatives have increasingly shown promise to coherently explain the observations and to predict new phenomena.

No, they haven’t. It would be more accurate to say “non-Big-Bang alternatives have continued to make no new correct predictions, while remaining inconsistent with well-established laws of physics.”

We believe, therefore, that a shift in effort in cosmology to these alternatives is essential if the field is to advance.

Yes, you do believe that! But it’s not true. So only half credit there.

The good news is, the crackpots are planning to get together at a conference. I am sure it will be an entertaining event. The thing about crackpots is, they are usually not mutually self-reinforcing; there are a potentially infinite number of directions in which one can be idiosyncratically mistaken, and crackpottery tends to diffuse through the space. So they aren’t likely to be happy with one another’s ideas. But at least they will be able to take refuge in a common feeling of persecution by the all-powerful Big Bang Establishment.

My latest nominee would be from Scott Lemieux at Lawyers, Guns and Money (which by itself is in the running for best blog title ever): “Life: It’s the Period Before You’re Born and After You’re Vegetative“. There’s some good content there, too.

See also Bitch, Ph.D. for more on the young girl who is already more articulate and sensible (not to mention courageous) than any of our nation’s important politicians.

Atrios is right: this is an excellent article by Fareed Zakaria on the wet martini.