PhysicsJANUARY 2005 physicsweb.org WorldVOLUME 18 NO 1 Einstein 2005 CONTENTS JANUARY 2005 Physics 3 POST-DEADLINE World Drawing a line under a force microscope, the physics of sound in the Sahara, how does water boil? 5 NEWS AND ANALYSIS Local difficulty for the cosmic background, Google targets scientists, massive Antarctic neutrino detector takes shape, ups and downs for physics departments in UK universities, contract to manage Los Alamos goes up for grabs 13 EINSTEIN 2005 Ahead of his time Peter Rodgers A brief history of Albert Einstein Matin Durrani Brownian motion – atoms made real 19–22 Einstein and the International Year of Physics Five papers that shook the world Matthew Chalmers NIVERSITY U 19 Einstein’s random walk Few physicists believed that atoms were real before Einstein’s theoretical TANFORD S work on Brownian motion paved the way for experimental confirmation, as Mark Haw describes The 1919 eclipse: a celebrity is born Matthew Stanley 27 Relativity at the centenary As we enter a new era of experiments, Einstein’s general theory of relativity remains the leading theory of gravity,as Clifford M Will explains Relativity – putting Einstein to the test 27–32 Einstein and his love of music Brian Foster CERN Looking after the image of a legend Peter Gwynne 37 The search for gravitational waves The detection of ripples in the fabric of space–time is one of the outstanding challenges in experimental physics. Jim Hough and Sheila Rowan report on progress A very special centenary Robert Bluhm Strange ways of light and atoms Charles W Clark Quiz: Do you play dice? Gravitational waves – still searching 37–41 47 The power of entanglement Einstein disliked the random nature of quantum mechanics but he was still LATT B influential in the development of the theory,as Harald Weinfurter relates AINER R ND A The other side of Albert Einstein Tim Chapman ALER -K The king is dead. Long live the king! Robert P Crease CHMIDT S Einstein’s quest for unification John Ellis ERDINAND F 58 CAREERS How to be a patent attorney Simon Mounteney Once a physicist…Wolfgang Heckl, careers update, movers and shakers Quantum mechanics – entanglement 47–51 63 RECRUITMENT Physics World is published monthly as twelve issues per annual volume by Institute of Physics Publishing Ltd, Dirac House, Temple Back, Bristol BS1 6BE, UK 72 LATERAL THOUGHTS United States Postal Identification Statement Physics World (ISSN 0953-8585) is published monthly for An evening with the Einsteins Lady Neysa Perks $400 per year within the United States. Periodicals postage paid at Melville, NY, and additional mailing offices. POSTMASTER: Send address changes to Physics World, American Institute of Physics, Suite 1NO1, 2 Huntington Quadrangle, Melville, NY 11747-4502. P HYSICS W ORLD J ANUARY 2005 physicsweb.org 1 POST-DEADLINE Microscopic ‘pen’ rewrites the rules Physicist solves Scientists in the Netherlands have modified and 14 nm deep in a chromium surface. an atomic force microscope so that it can The team used the technique to draw and desert mystery write and etch sub-micron patterns on a etch straight lines, but any pattern could, surface with molecular “ink”. Atomic force in principle, be created. It might also be microscopes (AFMs) were originally de- possible to reduce the width of the lines and signed to study surfaces by monitoring the the trenches further by sharpening the tip interaction between an extremely sharp of the AFM. “tip” and the test material, but they can be Elwenspoek and co-workers say their de- used for surface modification as well. In the vice is an improvement on existing AFM- new device the ink flows from a reservoir based surface-modification techniques, like through a microfluidic channel in the canti- “dip-pen lithography”, because it can hold lever that holds the tip and then on to the more ink and the flow of the ink can be con- tip itself (S Deladi et al. 2004 Appl. Phys. Lett. trolled more precisely. Moreover, by cre- 85 5361). ating a local environment around the tip, Using 1-octodecanethiol as the ink, Miko the operation of the device is not affected Singing dunes – in order to study the sounds of Elwenspoek and colleagues at the Univer- by humidity in the atmosphere. desert sand dunes, Bruno Andreotti first had to sity of Twente drew lines just 0.5 µm wide The pen could be used in new nanofabri- trigger avalanches by sliding down the dune face. on a gold substrate. The ink reacted with the cation techniques to create 3D nanostruc- gold to produce a stable monolayer struc- tures, and the Twente team now plans to do From Marco Polo onwards explorers have ture on the substrate. In separate experi- further work on the device itself and also on told stories about strange sounds they have ments with a commercial etchant, the tip the ink, including improvements to its vis- heard in the desert. It is known that sounds was able to etch trenches just 0.3 µm wide cosity and wetting properties. are produced by sand dunes when they aval- anche, but the exact mechanism behind the phenomenon has remained a mystery.Now Boiling water inside a computer Bruno Andreotti of the University of Paris 7 has proposed that the sounds come from vibrations in the sand bed that have been excited by collisions between sand grains (B Andreotti 2004 Phys. Rev. Lett. 93 238001). “Singing dunes are one of the most puz- zling and impressive natural phenomena I have ever encountered,” says Andreotti. “The sounds can be heard up to 10 km away and resemble the beating of a drum or the noise of a low-flying jet.” The dunes pro- duce sounds that are as loud as 105 dB – 0 ps 1 ps 10 ps roughly equivalent to a car horn – and have frequencies between about 95–105 Hz. The French physicist took his equipment – including a microphone, digital audio tape and accelerometer – from Paris to the Atlantic Sahara in Morocco, which contains more than 10 000 crescent-shaped dunes known as barchans. The wind in the desert can erode the back of these dunes, causing sand to build up at the top. When too much sand has accumulated, an avalanche occurs and the dunes start to “sing”. Andreotti simultaneously measured vi- brations in the sand bed and acoustic emis- 20 ps 50 ps 75 ps sions in the air, and was then able to extract information about the frequency,amplitude Although the boiling of water is one of the best-known examples of a phase transition, what happens at the level of molecules during this apparently simple phenomenon is not so well understood. In particular, and the phase of these signals. He found little is known about the start of the process when regions of gas vapour begin to form in the liquid. Now that the vibrations in the sand behaved like Dirk Zahn of the Max Planck Institute for Chemical Physics of Solids in Dresden has taken a major step slow-moving elastic sound waves that were forward in the study of evaporation by simulating the behaviour of 256 water molecules at a temperature localized at the surface of the dune and had of 100 °C (D Zahn 2004 Phys. Rev. Lett. 93 227801). Even though this represents a volume of water of × × an amplitude that was about a quarter of just 2.1 2.1 2.1 nm, the computational demands of the simulation meant that the trajectories of the the diameter of an individual grain of sand. molecules could only be followed for a fraction of a microsecond. However, this was long enough to reveal the beginning of the phase transition, when vacuum cavities (yellow regions in the image above) “The sounds are produced when grains spontaneously form in the liquid phase of water as a result of the breaking of hydrogen bonds. Nearby drum against one another, exciting elastic cavities then begin to merge into larger vacuum domains, while others quickly disappear, and the water waves on the dune surface, with the vibra- molecules at the liquid–vapour interfaces tend to leave the liquid surface. Eventually these evaporation tion of the sand bed tending to synchronize events outnumber the competing process whereby the molecules return to the liquid phase. Zahn is now the collisions,” says Andreotti. “In many applying the technique, developed by David Chandler and co-workers of the University of California at ways the surface of the sand bed acts like the Berkeley, to other phase transitions such as the evaporation of alcohol during the distillation process. membrane in a loudspeaker.” P HYSICS W ORLD J ANUARY 2005 physicsweb.org 3 30 years of innovation Delivering expert solutions for vacuum, surface & nanoscience High Accuracy SPM – the Dream Machine for the Next Generation from PSIA Faster! Easier! Accurate! At last, a truly new generation Scanning Probe Microscope has arrived. 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