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How the Sky Became Digital

W. Patrick McCray

A GRAND AND BOLD THING: An Extraordinary New Map of the Universe Ushering in a New Era of Discovery. Ann Finkbeiner. xii + 223 pp. Free Press, 2010. $27.

When asked in 1991 what he would do with the next generation of telescopes, Caltech astronomer Wallace Sargent said, “Pardon the expression, but I point the [expletive deleted] telescope at the sky and see what’s out there.” This expressive quote leads off A Grand and Bold Thing, a new book by award-winning science writer Ann Finkbeiner. What Sargent doesn’t say is also important: How you point the telescope to see what’s out there matters too. And, as Finkbeiner’s narrative illustrates, the ways in which astronomers do science have changed in remarkable and, at times, disquieting ways over the past two decades.

Finkbeiner focuses her story on the Sloan Digital Sky Survey (SDSS). Located at the Apache Point Observatory near Sunspot, New Mexico, the Sloan telescope uses its 2.5-meter mirror to take wide-angle images and spectra over wide swaths of the night sky. Compared with behemoths like the Keck telescopes in Hawaii, the Sloan is almost puny. But, as Finkbeiner explains, its considerable power stems not from the size of its mirror but from the enormous amounts of data it produces nightly. Those data contribute to an evolving “virtual observatory,” a vast digital archive that researchers from around the world can access without ever having to leave their offices.

Finkbeiner begins her account in 1987 with Princeton astronomer James Gunn’s proposal that a “digital telescope” be constructed that would use the larger detectors that were becoming available, which were based on charge-coupled devices (CCDs). Administrators from Princeton University, the Institute for Advanced Study and the University of Chicago soon put together plans for a “science factory” that would churn out gigabytes of data for their scientists to study. However, as the project’s price tag climbed from $12 million to more than $85 million, a growing consortium of patrons (including the Alfred P. Sloan Foundation, which gave millions of dollars and a name to the telescope) was needed to fund and staff the project. Once federal funding agencies got on board, it became clear that the data the survey produced would be available to the entire science community and would foster a greater democratization of science.

The main part of the story unfolds during the 1990s, when the astronomy community was revising its established practices of instrument building. A key challenge, and an expensive one, for the “Sloanies” was that before the surveying could commence they first had to create an instrument that, with its data pipelines, special software and databases, would be far more than just a telescope sitting on an isolated mountain peak.

After years of planning, the construction of hardware began in 1992, and the telescope and camera were supposed to be ready to begin a year of testing in 1994. But nothing went as planned. Everything fell far behind schedule, and the software was latest of all. Designing software to process and archive data collected by the telescope began to consume the careers of many postdocs and other “invisible technicians,” some of whom were frustrated to find themselves working primarily as programmers rather than astronomers, and for much longer than they had expected.

By 1996 complaints were being made that SSDS was “a completely unscheduled project, just like Italian trains.” At least trains in Italy did eventually arrive, though, however late they might be, whereas Sloan’s schedule often seemed to be slipping a month for every month that passed. Eventually the astronomers involved, who were more accustomed to the “lone investigator” model of doing astronomy, were obliged to accept, if not like, professional managers, with their scheduling charts, work-flow graphs and other tools. They were also forced to come up with verifiable science requirements for the survey—to decide, for example, that stars’ positions must be measured to within so many milli-arcseconds. Nevertheless, problems continued to dog the project, and at times it appeared as if the entire SDSS effort might fall apart—sometimes literally, as when engineers discovered in 1999 that the secondary mirror on the telescope had cracked.

As the instrument culture of astronomers changed, new ideas about intellectual property emerged as well, as they moved from what Jerry Ostriker called “the mine, mine, mine syndrome,” in which the data collected are a scientist’s personal property, to the mining of data archives. Finkbeiner describes clearly how scientists have used data collected by SDSS (and its successors, SDSS-II and SDSS-III) to redraw maps of the universe and gain a better understanding of how phenomena like dark energy and dark matter contributed to its morphology.

From the story of SDSS, we also glimpse a set of dyads that speak to broad sociological questions that astronomers and other scientists are still grappling with. One of these is the status of the instrument maker relative to that of the observer or the theoretician. Building new pieces of equipment is a career-consuming process, and the concerns voiced by postdocs who devoted years to SDSS in the hope of one day doing science with it ring true. Finkbeiner deserves credit for revealing the edifice of students and anonymous engineers that supports the careers of senior tenured scientists at research universities.

By the end of the book, Jim Gunn has become a Moses-like figure—he helped conceive SDSS and devoted more than a decade to building it, but he never realized the promised land of major scientific results. The rapidly changing computer technologies essential to Sloan, Finkbeiner writes, outpaced Gunn’s willingness to find the time to keep up with them.

However, I don’t think that SDSS itself has “changed the way astronomy is done,” as Finkbeiner maintains. Many factors contributed to this transformation, including the growth in size of the astronomical community, the routinization of multiwavelength research, and the fact that research ambitions superseded the traditional single-principal-investigator mode. Just as critical was the increased power of technology as computer performance and data storage became exponentially cheaper during the 1990s. At one point, the Sloanies imagined releasing their initial data on 19,000 CD-ROMS, an idea that today stirs a chuckle, given the data-holding capacities of even an iPod. In the end, SDSS appears to have been less a catalyst for the changing practice of astronomy than a symptom of it.

As astronomers are making plans to build the next generation of telescopes, with cost estimates closing in on the magical billion-dollar mark, one can question whether this transformation in how science is done has been an unalloyed boon for astronomers. I recall meeting a Stanford graduate student a few years ago who said he did observational astronomy. So I asked him which telescopes he liked to work with. As it turned out, none yet. For him, being an observer meant sifting through data collected by other people. SDSS provided an important bridge between older efforts, such as the famous 1950s-era National Geographic Society–Palomar Observatory Sky Survey and more ambitious efforts that lie in the future, such as the Large Synoptic Survey Telescope, which will generate terabytes of data every night. But with so much information available to them, have professional astronomers become alienated, as Marx might have said, from the means of production?

Finkbeiner’s book also raises questions about how ordinary citizens view the discovery process. Toward the end of the book, she writes enthusiastically about the hundreds of thousands of people who have joined the Galaxy Zoo project. Launched in 2007, it enables science buffs to “collaborate” with professional astronomers and classify galaxies using the Web. It has produced notable discoveries. For example, a Dutch schoolteacher scanning Galaxy Zoo images on her home computer found an extraordinary object—blue in Sloan’s initial images, but revealed in later analyses to be an eerie green gaseous cloud, illuminated perhaps by a jet of energetic particles from a nearby black hole. The project is a great way to get people interested in science, to be sure. But how does it compare with the grand and bold experience of being outside with a telescope, peering up at the sky?

W. Patrick McCray is a professor in the Department of History at the University of California, Santa Barbara. He is the author of several books, including Giant Telescopes: Astronomical Ambition and the Promise of Technology (Harvard University Press, 2004) and Keep Watching the Skies! The Story of Operation Moonwatch and the Dawn of the Space Age (Princeton University Press, 2008).



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