Canonical Prophet

BOOKS & ARTS COMMENT

for a means of doing so became his lifelong quest. A trio of papers that DeWitt published in 1967 is at the heart of the field. The Tril- ogy, as it is known, is lucid, visionary and packed with results. The Pursuit of Quantum Gravity: The papers cover two Memoirs of Bryce approaches to quan- DeWitt from 1946 tum gravity. The first to 2004 publication describes CÉCILE DEWITT- the ‘canonical MORETTE approach’ that served Springer: 2011. 147 pp. $49.95 up the Wheeler– DeWitt equation (also named after relativist John Wheeler) for the quantum evolution M. GIBERNAU (STUDIO PYRÉNÉES CERET)/REPRODUCED COURTESY C. DEWITT-MORETTE COURTESY CERET)/REPRODUCED PYRÉNÉES (STUDIO M. GIBERNAU of the geometry of space. The second and third papers develop a ‘covariant approach’ to quantizing gravity, which considers the sum of all the possible configurations a sys- tem can have in space and time, and is an extension of a method that Richard Feyn- man applied to quantum mechanics and quantum field theory. DeWitt, the book reveals, much preferred the covariant approach, openly ruing the day he came up with the Wheeler–DeWitt equation, which treated space and time separately rather than as a combination. His work on the covariant approach went on to play a key part in quantizing the electro- magnetic, weak and strong forces during the 1960s and 1970s. The canonical approach also influenced Stephen Hawking and The DeWitts worked together on the unresolved problem of quantum gravity for more than 50 years. others in their proposal of a “wave function of the Universe”. BIOGRAPHY The Trilogy was the sacred creed of quantum gravity for decades, and DeWitt was the prophet. He was a biblical char- acter in many ways. Raised in California Canonical prophet in a devoutly religious family (although he kept his distance from religion in later life), DeWitt had the towering, stern pres- Pedro Ferreira is inspired by a treasury of recollections ence of a church elder. When he walked of physicist Bryce DeWitt by his widow Cécile. into a room, backs straightened. He would leave a seminar if he thought it was not worth his while. He had no time for slop- he search for a theory of quantum Although the digressions into obscure piness; things had to be done properly. gravity — the marriage of quantum aspects of quantum gravity will challenge Once ideas were published, they were set mechanics and general relativity — some readers, the erratic narrative gradu- in stone. Tis the ultimate frontier of physics. It remains ally builds up an impressionistic tableau DeWitt loved to travel, considering unfinished business, and its creative fer- of DeWitt’s remarkable journey through himself a “space traveller”. He enlisted as a ment has attracted many vibrant people, postwar physics. US Navy pilot in January 1944 but did not not least Bryce DeWitt, one of the found- DeWitt’s interest in quantum gravity see any combat. Following his graduate ers of the field. In The Pursuit of Quantum began in the late 1940s when he was studying studies in Harvard during the late 1940s, Gravity, his widow and long-time research quantum field theory with Julian Schwinger he hopped around the globe, working at collaborator Cécile DeWitt-Morette offers at Harvard University in Cambridge, Mas- Princeton University, a personal view of the great man. sachusetts. Struck by gravity’s “splendid iso- NATURE.COM at the Swiss Federal This is not a typical memoir, but a lation” in the canon of fundamental forces, For a biography Institute of Technol- fascinating collage of essays, letters and DeWitt asked: “What if one simply dragged of physicist Hugh ogy in Zurich and, in commentary that is like a treasure chest: it forcibly into the mainstream of theoreti- Everett III, see: what Steven Weinberg a stack of priceless, dusty heirlooms. cal physics and quantized it?” His search go.nature.com/4zk9oz judged a “sojourn

[that] did not make good professional GEOGRAPHY sense, but … suited his roving spirit”, at the Tata Institute of Fundamental Research in Mumbai, India. In 1973 he led an expedition to Mauritania to Islamic views of Earth repeat Arthur Eddington’s 1919 measurement of the gravitational bending of A magisterial series revolutionizes our understanding starlight around the Sun’s limb during a of Arabic geography, finds Celâl Şengör. solar eclipse. Cécile and Bryce were also known for taking long walks in the stun- ning landscape of the American West cientific geography was invented by Geschichte des Arabischen Schrifttums, and in the Alps, where Cécile set up the the Greeks in the sixth century bc and Band XIV. Anthropogeographie Teil I: Les Houches scientific lecture series. reached its apogee in the mid-nine- Gesamt- und Ländergeographie; Stadt- und Regionalgeographie DeWitt’s academic career was colourful Steenth century in Europe. In this five-volume FUAT SEZGIN and varied. After his postdoctoral fellow- work, Geschichte des Arabischen Schrifttums J. W. Goethe Univ.: 2010. 553 pp. €124. (In German.) ships, he worked (History of Arabic Literature) — the last two in California of which were published in 2010 — science Geschichte des Arabischen Schrifttums, “The book made Band XV. Anthropogeographie Teil II: me want to take from 1952 to historian Fuat Sezgin shows that Muslim Topographie, Geographische Lexika, up the challenge 1955 at the Law- scholars played an integral part in developing Kosmographie, Kosmologie, Reiseberichte of quantum rence Livermore Greek ideas about the planet, and explains FUAT SEZGIN gravity, to Laboratory with how influential their work was in the West. J. W. Goethe Univ.: 2010. 470 pp. €117. (In German.) follow the Edward Teller By reviewing and analysing a vast corpus extraordinary on modelling of Arabic geographical writings from the work Measurement of Distances Between trail to that nuclear artillery eighth to the seventeenth centuries, Sezgin Known Places on Earth. shells. He briefly revolutionizes our view of the history of The many maps produced as a result of untamed led the Institute geography. The first three volumes, plus an these activities by Muslim scholars even- frontier of of Field Physics atlas, cover the development of mathemati- tually reached Europe. Beginning with physics.” at Chapel Hill, cal geography and cartography. The latter portolan maps in the fourteenth century North Caro- two volumes span a range of topics, from — predecessors of accurate navigational lina, a centre funded by the industrialist the history of general and regional geogra- charts showing coastlines and harbours — Agnew Bahnson, who hoped to unlock phy, through topography and cosmology to they influenced the European cartography technology from basic research in grav- the history of Arabic–Islamic travel reports. of Asia, Africa and the Indian Ocean until ity. In 1973 DeWitt ended up, along with He brackets these as well into the nine- Cécile, at the Center for Relativity at the ‘anthropogeography’ teenth century. University of Texas at Austin, which was to underline their Sezgin’s two most at the heart of the revival of research inter- relevance to human recent volumes go est in general relativity in the 1960s. existence. beyond cartography. SEZGIN F. Sadly lacking from the book is a In the first three Arabic geographi- personal description of the DeWitts’ books, Sezgin estab- cal activity started epic love story. Bryce and Cécile were lishes that Muslim before the seventh together for more than 50 years and had scholars — starting century ad, he four children. According to the publi- with geographers explains. Much geo- cation list, the couple wrote their first during the reign of graphical informa- paper together in 1952 and their last in al-Ma’mun (786– tion was included 2004. Yet we learn little about their joint 833 ad), a caliph of in poetry — the lives. There are scraps of information: Abbasid — inher- names of places, Bryce mentions that he “cast glances” ited and developed oases and other at Cécile in 1949, when he met her at the geographical watering sites. So the Institute for Advanced Studies in and cartographical the first geographi- Princeton. A picture of Bryce and Cécile tradition of the Per- A world map by ninth-century Muslim geographers. cal publications in is captioned with a quote from one of sian Sassanids and Islamic culture were DeWitt’s obituaries: “They became life- Greeks, from Eratosthenes to Ptolemy. The penned by philologists in the second century long sparring partners.” I would have Muslims improved on Ptolemy’s database of of Islam, following the expansion of the Ara- liked to have known more. longitudes and latitudes of features such as bic empire under the Umayyads and then the Nevertheless, the book is enthralling. cities, mountain ranges, rivers and continen- Abbasids. The first map by a Muslim author It made me want to take up the chal- tal coastlines. — a remarkable map of the world in the form lenge of quantum gravity, to follow the They initiated geodetic work in the ninth of a bird — was made in the seventh century extraordinary trail set down by Bryce century ad by re-measuring the length of a by a young friend of the prophet Moham- and Cécile to that untamed frontier of degree of meridian in the plains of Mosul mad, ‘Abdallah b.’Amr b. al-Āș. physics. ■ and Damascus and at Mount Casius, or The demand for broader Muslim geogra- Jebel Aqra, near Hatay (ancient Antioch) in phies grew as European interests expanded Pedro Ferreira is a professor of present-day Turkey, and by fixing the posi- beyond its borders astrophysics at the University of Oxford, tions of geographical features on the basis of NATURE.COM from the fourteenth Keble Road, Oxford OX1 3RH,UK, and astronomical observations. In the eleventh For more on Islamic to the sixteenth cen- author of The State of the Universe. century, this culminated in Turkish scholar history of science: turies. Travellers e-mail: [email protected] Abu Rayhan al-Biruni’s (973–1048) great go.nature.com/gbibpz hunted for works on