In search of weighty matters

books and arts In search of weighty matters AIP EMILIO SEGRE VISUAL ARCHIVES A hard look at the 45-year quest to detect gravitational radiation. Gravity’s Shadow: The Search for Gravitational Waves by Harry Collins University of Chicago Press: 2004. 864 pp. $100, £70 (hbk); $39, £27.50 (pbk) Virginia Trimble A distinguished colleague advised me not to review Harry Collins’ book to “avoid the controversy”. I think, however, that no dis- cernible controversy remains. The physics and astronomy community has recognized for 30 years that gravitational radiation exists but that Joe Weber didn’t discover it (roughly the first half of the book). And in the past decade, a particular sort of detec- tor, called a free-mass interferometer, has pretty much wiped the competition off the face of the Earth (the second half of the book). The best-known and most expensive (well, it’s American) version of the winner is called LIGO, the Laser Interferometer Gravi- tational Wave Observatory. Collins describes carefully how it won out over bar and sphere detectors and how it has (so far) been designed, managed, built and debugged. The single most salutory lesson he draws is that “the more money you want to spend on science, the less expert will the decision makers be”. What is gravitational radiation? Well, to produce light (electromagnetic radiation) you wiggle electric charges around; to pro- duce gravitational radiation you wiggle masses around. There are technical differ- ences in the polarization, for example, but the main difference is that gravitational radi- ation is the weaker by a factor of 10 40 . This means the masses that wiggle have to be of astronomical size to stand any chance of detection, so billion-dollar projects are currently under way to try and achieve this. Collins is director of the Centre for the Study of Knowledge, Expertise and Science at Cardiff University, UK. The search for gravitational radiation (waves in current parlance; he explains why) has been his most abiding interest, with the interviews reported in the present volume dating from 1972 to 2003. The book is not very easy going for a physical scientist. I caught at least 50 techni- cal terms and concepts whose meanings I could not have guessed or would have guessed wrong, because (like energy and momentum in physics) they are everyday words used in non-everyday senses, such as moral integration and colonial cringe. Is it worthwhile for a natural scientist to master some of these? Probably. Ornithol- ogy, pace Richard Feynman, is useful to birds through the designation and protection of Looking for clues: Joe Weber used bar detectors in the 1960s to search for gravitational radiation. endangered species, although the birds don’t know it. Collins coins the term ‘Pascalian funding’, for instance, to describe why government agencies in 1984 began supporting Weber’s work on coherent neutrino scattering (with principles later applied to bar detectors for gravitational waves). The idea is that some things would be so important if they worked that investment makes sense even if there is only a very small probability of success. Pascal had in mind belief in a deity. The coherent neutrino process would have made submarines clearly visible under the oceans via emission from their nuclear reactors, though the explanation given of the physics is unclear because the author fails to mention the closest working analogy,Mossbauer scat- tering of gamma rays. The Star Wars missile defence system and cold fusion, whose fund- ing has puzzled many physicists, probably also come under the Pascalian rubric. Collins’ discussion of evidential collec- tivism and individualism should ring bells with astronomers who have noticed the very different data release patterns of the Sloan Digital Sky Survey (let it all hang out) and the Wilkinson Microwave Anisotropy Project (release nothing until the team agrees, and then only a final product) and supposed that one must surely be wrong. Both can be right. The Sloan team are evidential collectivists who wish to involve the wider community in the process of assessment from an early stage, while the Wilkinson team are evidential indi- vidualists who believe they should take full NATURE | VOL 433 | 17 FEBRUARY 2005 | www.nature.com/nature responsibility for the validity and meaning of a result before it leaves their laboratory. New in this book is a metaphor of a dam of generally accepted ideas and experimental results holding back a lake of active work, within which a small island holds a few unconventional workers, Weber of course among them. Add the now common phrase “voted off the island”, and you will have a fair picture of what happened. Between about 1972 and 1976, most of the physics commu- nity decided that the early reports of evidence for gravitational radiation could not have been right, and thereafter reacted to publica- tions and conference talks by Weber and his colleagues as if they simply did not exist. The author misses some points. A foot- note mentions that the two messiest offices he ever saw were those of Weber and of Ron Drever, architect and major builder of the 40-metre prototype for LIGO, who was summarily removed from the team in 1992. Collins seems not to have realized that each had been suddenly evicted from a large labo- ratory and was required on almost no notice to squeeze many years of notes, records and spare parts into an average-size faculty office. Contributory expertise is what is needed to do science. Interactional expertise is sufficient for communicating about it: “You listen a good low-temperature physics,” as Lev Landau once said to the wife of a col- league. Collins describes himself as having interactional expertise in gravitational-wave detection, but might have benefited from additional advice by contributory experts. © 2005 Nature Publishing Group