A Grand and Bold Thing: An Extraordinary New Map of the Universe Ushering in a New Era of Discovery

  • Ann Finkbeiner
Free Press: 2010. 240 pp. $27 9781416552161 | ISBN: 978-1-4165-5216-1

A hundred years ago, only a few astronomers had regular access to telescopes that allowed them to make the discoveries that built their formidable reputations. In the mid-twentieth century, social change gave rise to national observatories that served a far greater constituency. The past decade has seen another major shift in astronomy: the Sloan Digital Sky Survey has opened up the northern sky to anyone with a computer.

A Grand and Bold Thing tells the story of the Sloan survey, which has mapped and digitized hundreds of millions of galaxies using a dedicated telescope in the New Mexico desert since 2000. With unfettered access to e-mail archives, science writer Ann Finkbeiner offers a fly-on-the-wall account of this ambitious programme, from the politics of its formation to its eventual success as one of the most highly cited projects in astronomy.

The survey was conceived by astronomer James Gunn of Princeton University, New Jersey, after the launch of the Hubble Space Telescope, in which he was also involved. Frustrated that management clashes between universities and NASA had allowed the orbiting observatory to be flown with flawed optics (since corrected), he turned his attention to a scheme to map the brightness and spectra of millions of nearby galaxies.

Finkbeiner reveals the complex negotiations that were required to get the survey off the ground. A set of elite US institutions — Fermilab, Princeton and the Institute for Advanced Study — initially got together to secure funding for the project from the US National Science Foundation and the Alfred P. Sloan Foundation. Several more university departments joined later. The different styles of the bodies involved led to near-fatal tensions within the project. “The trenches are dug, the war has started,” remarked Gillian Knapp, a senior project scientist on the Sloan survey. Finkbeiner summarizes the factions succinctly: “Fermilab is intransigent, Chicago is disengaged, Princeton is arrogant.” Fortunately, as the technology proved itself and the inevitable success of the project became clear, the organizations learned to work together.

The Sloan Digital Sky Survey uses this innovative 2.5-metre telescope to scan the northern skies. Credit: SLOAN DIGITAL SKY SURVEY; http://WWW.SDSS.ORG

The Sloan survey's power lies in the design of its telescope. After the eighteenth-century discovery by English astronomer James Bradley of stellar aberration — the shift in stars' positions due to the motion of Earth — improvements in differential measurement have heralded astronomical breakthroughs. The Sloan project is no exception. The telescope's precision in recording brightness in five bands of optical wavelength allows the accurate selection of objects from a catalogue of astronomical sources on the basis of their brightness and colour, from which physical trends and unusual objects can be derived. The telescope can scan much of the northern sky over several years with a camera that, a decade ago, was the largest of its kind.

There is huge pressure on individual astronomers to get involved with big projects or lose out.

Finkbeiner's explanation of the hardware is solid. She veers from the mundane to the unexpected, telling us, for instance, how the telescope once lost its tracking because of moths getting crushed on the instrument's drive. After experimenting with jangling keys and lasers, technicians found that two puffs of air per second kept the moths at bay. She describes many scientific results derived from the survey, such as measurements of galaxy clustering and the identification of distant quasars. But she emphasizes the contributions of US astronomers over those of others, writing Australian and UK scientists out of the discovery of quasars and 'acoustic' features in the distribution of local galaxies, for example. And a lack of quotes from outsiders means that we do not get a broad perspective of the survey.

The book highlights how the culture of astronomy is changing to one of 'big science'. Gunn has stated that “lone-astronomer days are over”, with the subject becoming so vast that it can be tackled only by large groups armed with computer code. The origins of this 'industrialization' lie in part with one of Gunn's Princeton astronomy colleagues, the late Bohdan Paczynski. In the 1980s, he proposed that “dark compact objects” might act as gravitational lenses, temporarily brightening background stars by distorting their light as the compact masses moved in front of them. These one-in-a-million events should be detectable, he suggested, by monitoring millions of stars with an automated telescope, a battery of computers and an automated software pipeline. A US–Australian team succeeded in detecting the objects by such a technique in 1993.

The emergence of a new generation of graduate students and postdocs who are “born wired to write code” is credited as essential to interpreting the vast data sets of modern astronomy. Astrocoders entertain us with their impressive films of stars falling into black holes, galaxies in collision and the birth and evolution of the Universe. Yet Finkbeiner does not explore the deeper question of how we should move from this information overload to physical understanding. With so many free parameters, it is debatable how robust these computer models are, what exactly we learn from them and to what extent they are falsifiable.

The availability of vast databases also affects the nature of the research. I fear for the loss of individuality in approaches and for niche projects that would otherwise open up new areas of exploration. Every new survey sparks a rush of comparisons with existing surveys at other wavelengths; this might exponentially boost the literature but it does not benefit our understanding to the same degree. Confirmatory results abound, and networked citations between groups foster a sense of success, irrespective of scientific outcome. As a result, there is huge pressure on individual astronomers to get involved with big projects or lose out.

Although A Grand and Bold Thing is more a celebration of Gunn's extraordinary career than a definitive account of the Sloan survey, it succeeds in capturing the arcane world of the professional astronomer. To Gunn's colleague at Princeton, Jerry Ostriker, it is almost a religious undertaking: “People will devote their lives, their time, their wits for things which have no practical importance. And there's something rather beautiful about that.”