OPINION sPriNG BOOKs NATURE|Vol 458|30 April 2009

An eye on the Einstein’s Telescope: The Hunt for and in the Universe by Evalyn Gates W. W. Norton: 2009. 320 pp. £18.99, $25.95

Gravitational lenses — heavenly bodies that bend light rays by their — have emerged as powerful tools in the astronomer’s repertoire. Yet their usefulness was difficult to foresee. In the 1930s, wrote it can be applied to many problems, from read, but one feels that the sceptically that “there is no great chance of the detection of invisible dark matter and author knows what she is observing this phenomenon”. Astronomer the magnification of very distant to writing about. Guiding the reader through Henry Norris Russell titled them ‘Perfect Tests the search for Earth-like planets around other multiverses, accelerated cosmic expansion or of that are Un available’. stars. Given the method’s power, one wonders the physics of exploding stars, Gates clearly Only the optimistic Fritz Zwicky predicted why it has taken so long for a book to be writ- explains the problems and challenges that that “the probability that … gravitational lenses ten about it. physicists face today. She uses apt analogies and will be found becomes practically a certainty”, Author Evalyn Gates is an active scientist original comparisons, many of which I had not although he did not live to see it. with a background in particle physics, cos- heard before. They are so appropriately chosen Einstein’s Telescope opens up this new view mology and public outreach. This combi- that I found myself eagerly awaiting the next of the Universe. Originally proposed as a semi- nation gives her the ideal tools to describe good metaphor. crazy thought experiment by Johann Soldner gravitational lensing. She addresses the book Gates discusses the major challenges in cos- in 1801, gravitational lensing was ignored for to the scientifically curious layperson — and mology. Not all of these questions will be solved more than a century until Einstein addressed delivers. Gates does an excellent job of direct- with gravitational lensing, but in many cases it it in a paper in 1911. Gravitational light deflec- ing readers through diverse astrophysical will contribute to the answer. Some of the top- tion made headlines when astronomers Arthur scenarios, including the ‘strong’ and ‘weak’ ics appear to be slightly out of focus; but then, Eddington and Frank Dyson measured offsets variants of lensing. She comprehensibly we learn, a does not have a in the positions of stars viewed near the Sun’s describes observations such as the distortion single focal point. edge during the solar eclipse of 29 May 1919, of background galaxies seen through a giant Einstein’s Telescope is comprehensive, includ- confirming a prediction of Einstein’s general cluster and the surge in the brightness ing a glossary and a good index, referencing . But it was another 60 years of stars caused by compact lenses moving in original literature and websites as well as offer- before the first double image of a lensed quasar front of them. ing detailed explanations of physical mecha- was discovered in 1979, and the technique’s use Gates uses the search for dark matter and nisms. It provides food for thought for both in cosmology began. dark energy — the two greatest mysteries in expert and general readers. Through Gates’s Conceptually simple, gravitational lensing modern physics and — as her main ambitious book, everyone will appreciate the occurs when a light ray is attracted by a cos- driver. With this in mind, she explores fields puzzles of the dark Universe — and the power mic body, its path becoming bent as if being from galaxy clusters to the searches for weakly and beauty of gravitational lensing. ■ focused by a lens. The amount by which the ray interacting particles and from distant super- Joachim Wambsganss is professor of astronomy is deflected is proportional to the mass of the novae to the cosmic microwave background. at Zentrum für Astronomie, Universität ‘lens’, and inversely proportional to the closest But she also touches on many other issues, such Heidelberg, Mönchhofstrasse 12–14, 69120 distance by which the ray passes the lens. Lens- as star and planet formation and galaxy evolu- Heidelberg, Germany. He is currently on ing is seen in astrophysical systems over a huge tion. She wants the reader to understand the sabbatical as Bohdan Paczyński Visitor at range of scales: from nearby stars and planets underlying physics questions. Some of these Princeton University, New Jersey 08544, USA. to distant and massive clusters of galaxies. And are complex, so the book is not always an easy e-mail: [email protected]

Quantum: Einstein, Bohr, and the Great Debate Physics of the Impossible: A Scientific about the Nature of Reality Exploration of the World of Phasers, Force by Manjit Kumar (Icon Books, £9.99) Fields, Teleportation and Time Travel in this popular history of quantum mechanics, Manjit by Michio Kaku (Penguin, £9.99) Kumar focuses “on the long-running debate between Theoretical physicist Michio Kaku looks at Niels Bohr and Albert Einstein, which took place various ‘impossibilities’ drawn from science from the mid-1920s through to the mid-1950s, over fiction. He asks how new technology might help the adequacy of the quantum theory as a framework us achieve currently impossible phenomena, for fundamental physics”, explained reviewer Don such as invisibility, and explains why others, such Howard (Nature 456, 706–707; 2008). as precognition, would break the laws of physics.

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