One beautiful Fall day seventeen years ago I wandered into an office and my life profoundly changed. I was an undergraduate at Princeton, and was looking for a thesis advisor. Jadwin Hall was an intimidating place. Plenty of names familiar from my textbooks. Nobel laureates scattered about. And we were expected to just barge into their offices, and ask to work with them.

One office door was always open. As you walked by you could peek in, and see its occupant hard at work. Hunched over his notebook, scribbling away. Or standing by his bookcase, deep in thought. Most often at the blackboard, chalk in hand. This was John Archibald Wheeler, one of the legends of modern physics. He did foundational work on quantum mechanics, collaborating with Niels Bohr on some of the earliest work in nuclear fission. He invented the S-matrix. He played important roles in both the Manhattan project (atomic bomb) and the Matterhorn project (Hydrogen bomb). He made major contributions to general relativity, co-authoring with Charlie Misner and Kip Thorne the bible of the field. He was legendary for his way with words, coining such terms as wormholes, quantum foam, black holes, and the wave function of the Universe (the Wheeler-DeWitt equation). He trained generations of students; one of his first was Richard Feynman.

Fortunately, being a relatively clueless 20-year old, I was only dimly aware of these things. I was interested in gravity and cosmology, and I had heard Wheeler knew a thing or two about such topics. So I waltzed in, and asked if he had any projects I could work on. I staggered out of his office four hours later, laden with books, a clearly defined project in my hands. For the ensuing two years I spent essentially every weekday with Wheeler. Each morning I would rush over to his office, always to be greeted the same way: “What’s new?” I would have been up late the night before, desperately trying to find something interesting with which to answer that question. We would then spend hours working together, going over my results, scrutinizing my calculations, poring through the literature, brainstorming new ideas. Wheeler gave me a direct and personal introduction to the joys of research. We would break for lunch, and walk up to the faculty club. I often had trouble keeping up with him. He would always take the stairs (”No time to wait for an elevator!”). He would hook his arm into the banisters, and swing around, practically leaping from one flight to the next. This was 1990; Wheeler was 79 years old.

We would often work all afternoon (with the occasional interruption, the nuisance of having to leave for my class lectures). Every evening I would walk with him from Jadwin up across the full length of campus, to catch his bus. We would pass the corner of Ivy lane and Washington road, where he had scratched 137 into the concrete when they were pouring the sidewalk. We would pass Jones Hall, where he used to discuss relativity with Einstein. We would continue on through campus, crossing in front of Nassau Hall. Wheeler would insist we walk diagonally to the far gate, instead of exiting through the more convenient FitzRandolph Gate. An Undergraduate was not meant to exit FitzRandolph Gate until graduation, and Wheeler didn’t want to be responsible for what might occur were I to break tradition.

For two years I sat at the feet of the master, and I absorbed as much as I could. I learned about science, and about life. Wheeler had broad interests. We would often discuss biology, or history, or poetry. Over the ensuing years we kept in touch. We collaborated together on Wheeler’s last published paper.

Yesterday I spent a couple of hours at Wheeler’s bedside. I tried to say thank you. But it was impossible to convey how much he means to me, and how grateful I am to him. In that moment when I crossed the threshold to his office, I was embarking on a new path. I am still on that path, and every day I am grateful to him for showing me the way.

John Wheeler died this morning.

Gravitational waves were born from the mind of Einstein in 1918. He noticed that his brand-spanking-new field equations for the general theory of relativity had a simple wave solution in the weak field regime. These solutions represent propagating waves in the fabric of spacetime, traveling at the speed of light. In another fit of creative nomenclature these were dubbed “gravitational waves”. For a ring of particles floating in space, a passing gravitational-wave will cause them to oscillate (image at right stolen from the Wikipedia entry). For an introduction to the theory behind gravitational waves, I highly recommend chapter 7 of a certain textbook. (Sean, I get a kickback, right?)

Sadly, gravitational waves have had a fairly rough childhood. First came the doubters. There was much debate within the community as to whether gravitational waves truly existed. It might sounds strange that, given an equation describing their existence, gravitational-waves could nonetheless be questioned by large numbers of physicists. However, general relativity can be tricky, and it’s not always straightforward to understand what it’s trying to tell us. In this particular case, the question was whether or not gravitational waves were a gauge artifact. It can sometimes get confusing as to whether an effect is truly physical, or is just a byproduct of the coordinate system one has chosen. For example, look at the latitute/longitude coordinate system on the Earth. This system gets weird at the poles, where suddenly the longitude is no longer well defined (there are an infinite number of valid longitudinal coordinates for the same point). The North and South poles are somehow special, and if all you had were the coordinates, you might be afraid to take a walk there. Who knows what lurks at the singularities?! Needless to say, the problem is with the coordinates, and not with the poles themselves. (Although nowadays you might be afraid to head to the North Pole because you might end up under water. But don’t worry, Bush has it under control.)

Another example of the trickiness of coordinates, drawn from general relativity, is the black hole. In the canonical Schwarschild coordinates describing a black hole, it looks like terrible things (e.g., singularities) happen at the event horizon [or Schwarschild radius, which represents the ’surface’] of the black hole. But these are a problem with the coordinates. In truth, nothing particularly weird happens as you cross the surface of a black hole (besides gravitational lensing causing the sky to appear bent and warped). This can be seen by writing the exact same spacetime in different coordinates (e.g., Kruskal coordinates), where everything becomes well behaved (except for the singularity itself). No big deal crossing the event horizon (though all hell breaks loose as you approach the singularity). A similar confusion resided in the nature of gravitational waves. There were ways to rewrite the coordinate systems such that the waves appeared to disappear. Sir Arthur Eddington supposedly quipped that gravitational waves travel at “the speed of thought” (referring to a subset of waves which indeed are coordinate artifacts). In addition, many of the early calculations were done in the linearized, weak-field regime, where simplifying assumptions are made regarding the strength of gravity. Calculating the presence of waves in the full-blown theory is not nearly as straightforward. In Einstein’s original work he presented the “quadrupole formula”, which describes the energy loss due to gravitational-wave emission from a binary system, and which is actively used to this day. But the weak-field assumptions neglect self-gravity, which could be important in a binary system. Roughly 20 years after his initial proposal of gravitational waves, Einstein submitted a paper to the Physical Review with the title “Do Gravitational Waves Exist?”, with the answer “No”. (There’s a general rule that all paper titles in the form of a question have a negative answer.) The father disavowed his own children. We all make mistakes. (In this case, the referee rejected the paper. Einstein took great offense, and never again submitted to Physical Review. The referee was right. Einstein was wrong.) It took another 40 years or so for the community to develop a full understanding of how gravitational-waves fit into general relativity. They are now considered an essential component of the theory. A very interesting discussion of this history can be found in a paper by Daniel Kennefick.

One way to think about the necessary existence of gravitational-waves is through the following thought experiment. Imagine that you are on one side of a room, and that on the other side is a very massive object (e.g., a plutonium bowling ball). The lights are off in the room, but fortunately you are carrying a very sensitive gravitometer, so that you notice the force of gravity due to the massive ball: your gravitometer points right at the bowling ball. Now let us assume that Mark sneaks in, and gives the ball a good (preferably relativistic) kick. Since the ball has moved, the gravitational field should register the change. Newton tells us that the gravitometer would instantly adjust. But from relativity we know that nothing travels faster than the speed of light (including information), and therefore we need ’something’ to go from the accelerating bowling ball to our gravitometer, to tell it that the bowling ball has indeed moved. This is a gravitational wave! It carries with it the information about the accelerating mass, rushing out at the speed of light to announce the motion of the bowling ball to the entire Universe. Also notice that, were the bowling ball to suddenly contract, but remain spherical and conserve mass, then the gravitometer wouldn’t register a change. From this, we conclude that spherically symmetric variations don’t emit gravitational waves. As with most hand-wavy arguments, there are some important details being glossed over here (e.g., near vs far-field effects; Scott and Eanna have a nice review). But it makes a compelling case that something akin to gravitational waves must exist for general relativity to be self-consistent.

In a following post I’ll discuss the next sordid chapter in the history of gravitational waves.

The annual April meeting of the American Physical Society is currently underway. This meeting brings together thousands of physicists, from all branches except condensed matter. The condensed matter types have their own meeting (in March), which dwarfs ours. For the next few days, there will be a flurry of press releases originating in Jacksonville, Florida. Although I have been missing the action down south, there is one press release which was conspicuous in its absence. A measurement of frame dragging was not announced by the Gravity Probe B satellite (affectionately known as GP-B), as originally planned. Instead, NASA issued an Interim Report summarizing the state of the data analysis thus far. The press release is here.

GP-B is probably the oldest space experiment alive. The mission was first proposed in 1959, and funding began in 1964 (Francis Everitt, the Principal Investigator, has been involved from the very beginning). The science goal is eminently worthwhile: to measure the Lense-Thirring precession (also known as frame dragging) due to the Earth’s rotation. In general relativity a rotating mass will drag space along with it, leading to effects which would be completely absent in Newtonian gravity. For example, a gyroscope in polar orbit about the Earth will show an extra precession due to the Earth’s one-revolution-per-day spin. One of the problems with general relativity is that gravity is much too weak. Every time we come up with some cool effect (gravitational waves, frame dragging, time dilation), it turns out that it’s almost impossible to see the effect. Frame dragging is no exception. If we were near a rapidly rotating black hole, frame dragging would jump out at us: a gyroscope would wobble all over the place. But the Earth’s frame dragging, for an object in orbit 650 km up, adds up to a miniscule 39 milli-arcseconds per year (mas/yr). For some sense of how small this is, consider your average visible, bright star. For generations we’ve considered the stars to be fixed on the sky. As we now know, this isn’t entirely accurate, and the stars do indeed move. The record-holder is Barnard’s star, which moves by 10,000 mas/yr. Typical stars have proper motions closer to 100 mas/yr. In comparison to the effects of frame-dragging, the “fixed” stars are moving all over the place, which emphasizes the difficulty of measurement. GP-B monitors the orientation of the spin axis relative to a particular star (IM Pegasi). This star was specifically chosen because it is bright in both optical and radio, allowing its motion (against a background, fixed frame of distant quasars) to be exquisitely well-measured using radio telescopes (through Very Long Baseline Interferometry, incorporating data from the VLA). (If you’re wondering about GP-A, it was launched in 1976. It carried an atomic clock, and directly measured the time dilation due to the gravitational redshift, confirming relativity at the 0.01% level.)

If the only precession came from frame-dragging, the experiment might be somewhat more straightforward. The problem is that there are other physical effects which cause precession, and which completely overwhelm the signal of interest. The Earth is not a perfect sphere; it is squashed, being 43 km fatter around the equator than around the poles. This provides a convenient handle upon which gravitational tidal forces of the Moon and Sun pull, leading to a precession of 50,000 mas/year. There is also geodetic precession, which is a general-relativistic effect due to the curvature of spacetime about the Earth (and which would be present even if the Earth were not rotating). Geodetic precession is also comparatively large (6,600 mas/year), and is by now well established. It will need to be understood to an unprecedented degree before a measurement of frame-dragging is possible. The two main science goals of GP-B are the precision determination of both geodetic precession and frame dragging. Yesterday they announced a measurement of the former to 1%. A pretty picture from the GP-B website summarizes:

One major development in the intervening 40 years since GP-B was initially funded has been the use of the LAGEOS satellite system to independently measure frame dragging. These satellites were designed to be orbiting “test particles”, to enable geodynamic measurements of the Earth. They are nicely round and reasonably uniform, completely passive, and each is covered with 426 cube-corner retroreflectors. A retroreflector is just a box with mirrors on the inside walls, and one wall missing: a light ray coming in through the missing wall is bounced back in the direction it came from. (Commonly found in reflectors along highways, or reflecting tape in clothing/bags/shoes.) Apollo astronauts left some large retro-reflectors on the moon. One can shoot laser pulses at these, detect the returning photons, and precisely measure the position of the Moon (to better than a cm!). These lunar-ranging experiments turn out to be an important constraint on alternative theories of gravity. Similarly, the positions of the LAGEOS satellites can be precisely monitored, and the orbital evolution of two of the satellites can be used to accurately measure the precession. In this case, rather than using the spin of the satellite (or a gyroscope within it) as a reference, one uses the orbital plane of the satellite motion. [In the interest of full disclosure, it should be mentioned that my first refereed paper was an analysis of the effect of the Earth’s gravitational and magnetic field on the spin of the LAGEOS satellites. There are a number of important systematics which depend crucially on understanding this spin.] To use the LAGEOS satellites to measure frame dragging, the full gravitational field of the Earth needs to be accounted for (in particular, the mass multipoles due to the non-sphericitiy of the Earth). As it happens, the GRACE and CHAMP experiments have recently provided unprecedented maps of the Earth’s field. Incorporating these results into an analysis of the orbits of LAGEOS, a measurement of the Earth’s frame dragging was accomplished by Ciufolini and collaborators, at the level of ~10%. (Due to subtleties in the analysis there is some debate as to the ultimate precision of the measurement; but a confirmation of frame dragging is generally agreed upon.)

When GP-B was first proposed, measuring frame dragging seemed like a great idea. However, as the decades went by and GP-B was still far from launch, and as the price for the mission broke the $0.5 x 10⁹ barrier, enthusiasm for the experiment started to wane. In addition, general relativity has been tested in many independent ways at this point, and LAGEOS has confirmed that frame dragging is consistent with general relativity at the ~10% level. This is not to say that it’s not worth precisely measuring frame dragging; it’s just perhaps not the first thing on our list of worries. A number of review panels have been convened over the decades to evaluate the mission’s fate, and each time the mission has squeaked by. A study of the politics behind this mission would be quite interesting. My principal worry about GP-B is that there are essentially two possible results: either GP-B confirms general relativity (in which case everyone says great, and continues to do what they were doing), or GP-B claims a result inconsistent with relativity (in which case everybody questions the result). This is an extremely difficult experiment, and there are many ways for things to go wrong. And, for better or worse, nothing like GP-B will be done again in the near future, and so it will be highly non-trivial to independently test its results.

After many difficult years, the GP-B satellite was finally launched on April 20, 2004. The satellite is an amazing feat of engineering. This is truly a precision science experiment, but one that is being flown in the harsh environment of space rather than being lovingly tended to in a lab in the basement. The gyroscopes are superconducting spheres; the most perfectly engineered spheres ever produced (equivalent to a spherical Earth with no mountain (or valley) higher (or deeper) than 2.4 meters). The spins of the four independent gyroscopes, cooled to 1.8 Kelvin, were monitored for over a year. Although the satellite is still in orbit, at this point the liquid helium which cooled the gyroscopes has boiled away (by design), and the satellite is no longer taking precision data. At this point it remains to analyze the data sent from the satellite, and announce whether or not general relativity is correct.

Originally, yesterday was going to be the big press release circus where NASA announced the results of the mission. But the analysis has run into a number of snags. Even though the gyroscopes are very close to perfect spheres, tiny imperfections cause electrostatic patches on the surface of the spheres (and housing). This breaks the spherical symmetry, and causes a polhode motion. Although this effect was anticipated, it was thought that it would remain constant through the life of the mission. This has not turned out to be the case, and the time variation needs to be understood and accounted for in the analysis. In addition, the surface electrostatic patches interact with the rest of the spacecraft, causing miniscule torques (which vary with the relative alignment of the entire spacecraft about the axis of rotation). Until these effects are well under control, a definitive measurement of frame dragging is impossible. Yesterday’s announcement was that the geodetic precession has been measured to better than 1%, and agrees with the predictions. Although this is indeed an important measurement, it is not what everyone has been waiting for.

After over four decades, it is not unreasonable for the GP-B team to ask for a little extra time to check and double-check their results. It is to their credit that they are being deliberate and meticulous in their analysis. The final results are to be announced this coming December, hopefully leading to yet another important observational test of general relativity. And a conclusion to one of the most technically ambitious experiments ever launched into space.

Yesterday I took a pilgrimage to two holy sites:

Trinity
This was where the first atomic bomb was detonated, on July 16, 1945. The site is located on the White Sands Missile Range, and is open to the public twice a year. Needless to say, it’s in the middle of nowhere. You drive for miles across desert scrubland, to arrive at a fenced in area the size of a soccer field.

One morning over 60 years ago, the desert floor glowed brighter and hotter than the surface of the Sun. The bomb was detonated at the top of a 100ft steel tower. A small piece of twisted steel, one of the footings of the tower, is all that remains. As you walk the site, you notice little pieces of mottled greenish glass (think tiny shards of a beer bottle). This is trinitite: sand from the desert floor melted into glass by the explosion. After the explosion the entire crater floor was covered with trinitite, forming a green glassy bowl. Since then the trinitite has been bulldozed, though scattered pieces remain. We brought a Geiger counter, which provided the main indication that this patch of Earth is unlike your average backyard. At the epicenter the radiation level is roughly an order of magnitude higher than background levels. It is unnerving to be exploring a nondescript patch of desert while your Geiger counter clicks up a storm.

One becomes contemplative at the site. Holding a piece of trinite, you realize that it was forged at the instant of the birth of the atomic age. That this tiny piece of glass is a physical remnant of humanity’s loss of innocence.

Very Large Array
A couple of hours away from Trinity sits the Very Large Array (VLA), part of the National Radio Astronomy Observatory. The VLA is perhaps the single most publicly recognizable scientific installation. It is extraordinarily photogenic; the film Contact moved the observatory into the “A” list of movie stars. It is hard not to be impressed by its sheer scale: 27 radio dishes, each of them 25 meters (82 feet) in diameter and weighing 230 tons. The dishes move along 21 kilometer (13 mile) long train tracks, allowing for various configurations trading off resolution and field-of-view. These tracks are arranged into three arms radiating from a central point, forming a scientific trinity. This trinity has led to great enlightenment.

The receivers are in the 70 Mhz–50 Ghz frequency range, corresponding to wavelengths of 400–0.7 cm. Because these radio wavelengths are long, a much larger dish is needed to produce a resolution on the sky equivalent to optical telescopes. The angular resolution of a telescope can be approximated by: θ = λ/d, where θ is the angular resolution (in radians), λ is the wavelength of the observed radiation, and d is the diameter of the telescope. For reference, the full moon is ~0.5 degrees = 30 arcminutes = 1800 arcsec across, and 1 arcsec ~ 5e-6 radians. The center of the visible (optical) band of light, corresponding to the color green, has λ ~ 500 nm = 5e-5 cm. To image something green on the sky to 1 arcsecond (which optical telescopes routinely do) thus requires a telescope of size at least 10 cm. To make an equivalent image in radio frequencies (which have wavelengths roughly 100,000 times longer) requires a dish 100,000 times bigger: instead of 10cm, we need a dish 10 km across. There are two ways to address this: (1) Make a humongous dish. The Arecibo dish in Puerto Rico is 300 meters across. (2) Make use of interferometry. The VLA combines the data streams from 27 dishes to produce a single image, corresponding to a much larger single observatory. Each individual pair of dishes can be thought of as sampling an interference pattern of a point source, or measuring a Fourier component of the full brightness distribution of an extended source. With sufficient numbers of pairs, a detailed image can be reconstructed. The VLA has 27 dishes, and thus 26+25+24+..+1 = 351 separate pairs. In the A configuration, the dishes are placed at their furthest positions, leading to a maximum pair separation of 36km. This corresponds to the resolution of a single dish 36km across, with a collecting area (and thus sensitivity) of a single dish 130 meters in diameter. In its highest frequency band, and in its widest observing mode, the VLA has an effective resolution of 0.05 arcsec. At present the VLA is in D configuration, which is its most tightly-packed: all the dishes are within 1km of each other. In addition to having great resolving power, the VLA is extraordinarily sensitive. If you were sitting on the Moon trying to make a cellphone call, and the VLA pointed at you, you would completely overwhelm its detectors. Needless to say, all cellphones must be turned off on the VLA grounds. In addition, computers need to be shielded in metallic rooms (Faraday cages). Most importantly, the observatory has to be far from all possible interference. It is in a remote part of New Mexico, surrounded by mountains which act as natural shields. The VLA has been responsible for many spectacular discoveries, on everything from magnetars in our Milky Way to quasars at the far reaches of the observable Universe.

Both the Trinity Test site and the VLA are located in the New Mexican desert. Both are deliberately remote. And both are testaments to human ingenuity. They remind us of the tremendous and the terrible power of science.

In a follow-up to Julianne’s previous post on scientific communication, I thought I’d describe a lecture I attended last week. I’ll try not to say anything overly controversial (though CV readers can be a tough crowd). The talk was by Felice Frankel, as part of the Santa Fe Institute public lecture series. The title was “More than Pretty Pictures: The Power of Images in Science”. Frankel is known for her scientific photographs. She creates beautiful images of a large range of physical systems (from water droplets to nanocrystals). She’s been responsible for quite a number of cover images for journals such as Science and Nature.

Frankel spent much of her lecture discussing her philosophy in taking scientific images. This consisted mostly of comments about the power of visualization, and ideas for how to make scientific visualization more effective. She emphasized that it’s highly nontrivial to produce an image which grabs you, while simultaneously informing you about the science it’s meant to represent. Many scientific images are uninspired. Or confusing. Often both. The lecture was sprinkled liberally with her work, much of which is quite arresting. For example:

This is an image of a ferrofluid. Frankel took seven small magnets, and placed them below a glass plate with the fluid above. She then added a bright yellow Post-It note below, yielding the vivid colors. It is this last step which completely transforms the photograph, and which your average scientist would have neglected. We have much to learn in how to present our results, both within the community, and to the world at large.

Images are indeed an essential component of science. They are visceral and physical, in a way that a table of numbers cannot hope to reproduce. They allow for what Frankel terms “visual thinking”: a direct and unmediated engagement with the world. This is particularly evident in astronomy. I would argue that the Hubble Space Telescope has generated many of the most beautiful images ever produced. And an appreciation of the science underlying the images only strengthens one’s admiration. Astronomy is peculiar in that a large portion of the field is fundamentally based on pretty pictures. (Okay, some of these pictures are run through variants of prisms to produce spectra, which aren’t quite as beautiful (at least to my, untrained, eye).) Julianne is our resident expert on taking and interpreting astronomical images; I’m told it’s a little more involved than pointing a digital camera and pushing the button.

What I found most surprising about Frankel’s lecture was her repeated insistence that she is not an artist, and that her photos are not to be considered art. As she put it: “This is why I am not an artist: I am deeply committed to maintaining the integrity of the science.” In her view, because she is constrained to reproduce the world as it is, she is not allowed the free rein of an artist. Her focus is on communicating science as effectively as possible: education rather than aesthetics, meaning rather than art. I find this argument somewhat disappointing. Her most effective images are certainly art; in fact, a number of museums have added her photographs to their collections. And her ability to produce these images, without the liberty of composing unphysical scenarios, or the liberal application of photoshop, does not detract from her talents. If anything, the restricted domain in which she works emphasizes her abilities. Although the sonnet is a severely constrained form of expression, I don’t see anyone arguing that Shakespeare’s contributions don’t qualify as art.

One side-note which Frankel briefly touched upon was the issue of “true” or “accurate” representation in science. While Frankel makes an effort to maintain the essential integrity of her images, most Hubble images are somewhat enhanced (false-color). This means that, were you to manage to stick your head into the focal plane of the Hubble telescope (the fact that it’s hundreds of miles above the surface of the Earth notwithstanding), the image you would see with your eyes would look completely different from the postcards we’re all familiar with. Scientists have taken liberties with the color palette and contrast in producing the images. Often the frequencies of the light in astronomical images are well outside human experience. The human eye is a particular sensor, and there’s no reason that it “sees” the universe in a way that’s in any sense profound. For example, we don’t see infrared. If we did, a hot pan on the stove would glow as a warning, and all those times I have dropped spaghetti sauce all over the floor would have been avoided. We don’t see x-rays either (superman presumably does; but in his case his eyes must not only be sensitive to x-rays, but also emit them in the first place, since the Sun isn’t bright enough in x-rays to give him good images on Earth). There are interesting astronomical sources of light at essentially all frequencies we’ve cared to observe, and so we generate images in a tremendous range of wavelength bands. Furthermore, by playing with the contrast and color scale, we can highlight various features and structures in the images; perhaps we’d like to “see” star forming regions, or shocked gas, or interstellar dust. As a happy byproduct, we also make the images visually stunning. It’s probably not entirely happenstance that images which emphasize interesting science also happen to be more beautiful. Although you would never see the identical scene with your naked eye at a telescope, the images are no less physical or instructive. They represent good science and good aesthetics. What’s not to love?

Jim Gray, a major contributor to the Sloan Digital Sky Survey, has gone missing. From Rich Kron:

As many of you know, our colleague Jim Gray has been missing at sea since Sunday evening. He was sailing near San Francisco in good weather. He is a
highly experienced sailor, and the boat is well-instrumented. So far no
trace has been found, despite continuing, highly intensive searches.
He has had an enormous impact on our Collaboration. He has generously spent a large fraction of his time over the last 5 years to work with us to create the SDSS. Our thoughts are with him and his family, and we hope for his safe return.

There is an effort to help with the search. Details from Alex Szalay:

We are processing hi-rez satellite images with a 0.8m resolution into 512×512 JPG tiles. They are placed on a website for visual inspection. If you have a bit of free time over the weekend, please help in inspecting a few images.
It is a long shot, but everyone is getting pretty desperate. There is additional info, and in particular other images.

A news article on the search.

Being a cosmologist is a dream job. We spend our days (and nights) wondering about this vast and surprising and beautiful Universe we find ourselves in. Every now and then we make our own contributions, uncovering a clue, seeing just a little bit further. But we don’t often reflect on the miracles that are required for the field of cosmology to exist at all.

Human beings are natural-born cosmologists. Essentially all human societies have wondered about the origins of the cosmos. It is easy to imagine a world in which nobody cared about the age of the Universe; such questions have nothing to do with everyday experience, and are completely irrelevant for evolutionary success (in the strict ‘eating-sleeping-procreating’ sense). Nonetheless, part of being human seems to entail asking these “big” questions.

Perhaps even more surprising, contemporary society backs up its cosmological interest with cold, hard cash. Through gifts and taxes individuals make financial sacrifices, allowing science to exist and prosper. And this is not a trifling contribution. The total US investment in the basic physical sciences in 2006 was roughly $20 billion. US taxpayers spend about $70 per person per year, or $150 per household. Europe and Japan contribute similar amounts, and almost all nations contribute at some level. This is what pays for the beautiful images from Hubble. This is what allows us to figure out that there was a Big Bang, that the Universe is expanding, and that this expansion is accelerating. This is what allows us to continue to do what we do. Although funding is a struggle (especially this year, which is turning into a disastrous one for the sciences), the fact that it exists at all is wondrous.

But the greatest miracle is that cosmology works. The Universe appears to be comprehensible. It is possible to ask a question such as “How old is the Universe?”, and actually find an answer. Why are there so many clues? Why is it that, given enough careful observation and quiet thinking, we can actually figure this stuff out? We now have a description of the Universe which works remarkably well from a fraction of a second after the Big Bang to today, 14 billion years later. It’s truly astonishing.

Maybe the string of successes is about to end? It is conceivable that dark matter and dark energy, those mysterious elements which make up 95% of the energy density of the Universe, will remain “dark” to us forever. That we’ll never understand how the first stars formed, nor why galaxies look the way they do. Although this is possible, most of us are optimistic that there’s a long way yet to go. And we have history on our side. Thus far, nature, although coy, does seem to yield her secrets eventually. Science marches forward. Questions which once resided in the realm of metaphysics now have definitive physical answers. Why is the Universe comprehensible? As far as we know, it didn’t have to be this way.

However, without the generous contributions of society much of the Universe would remain incomprehensible. It thus seems appropriate to express thanks to our fellow citizens. It is through your munificence that this whole glorious enterprise is funded. This science belongs to you. From the preface to Gravitation, by Charlie Misner, Kip Thorne, & John Wheeler (affectionately known as MTW, or the telephone book):

We dedicate this book
To our fellow citizens
Who, for love of truth,
Take from their own wants
By taxes and gifts,
And now and then send forth
One of themselves
As dedicated servant,
To forward the search
Into the mysteries and marvelous simplicities
Of this strange and beautiful Universe,
Our home.