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Physics World Digest: August 2002 edition

August 01, 2002

Physicists see eye to eye with opthamologists
Glaucoma is one of the leading causes of blindness in adults - yet over half of us who have the disease do not realise that we are suffering from the condition. While the disease can be treated if caught soon enough, early diagnosis relies on regular screening programmes that can be expensive and labour intensive. Now, however, researchers at Heriot Watt University are developing a physics-based technique called "hyperspectral imaging" that could spot the disease well before it affects vision. Previously used for detecting minerals and oil seeps by satellite, it can provide biochemical information about the retina by measuring the intensity of light reflected form the back of the eye over hundreds of different wavelengths. (p. 24)
Contact: Joanne Lawlor, Department of Computing and Electrical Engineering, Heriot Watt University, Edinburgh, UK (tel. -44 (0)131 451 3328; fax +44 (0)131 451 3327; e-mail jlawlor@cee.hw.ac.uk)

Negative reaction to negative refraction
If you think that science is a smooth progression towards objective truth, then a dispute in the normally cordial world of optics might make you think again. The disagreement concerns the well-known phenomenon of "refraction", which explains why a stick appears to "bend" when half immersed in water. One set of researchers - led by John Pendry of Imperial College London - believes that a new class of materials can refract light rays "negatively". In other words, light entering the material at an angle would be bent away from the normal - rather than towards it as in conventional materials. These weird materials could be used to make "perfect lenses". But other researchers think that negative refraction defies fundamental physical laws. Although it is unclear which view is correct, neither side wants to give in without a fight. (p. 8)
Contact: John Pendry, Imperial College London, UK (tel. +44 (0)20 7594 7606; fax +44 (0)20 7594 7604 e-mail j.pendry@ic.ac.uk)

Paul Dirac: seeking beauty
The Nobel-prize winning physicist Paul Dirac, who was born 100 years ago this month, is best know for his prediction of "antimatter" and for shaping our understanding of the sub-atomic world. But the reclusive genius also believed - sometimes misguidedly - that mathematically "beautiful" theories were also the most powerful ones. He thought, for example, that if a mathematically beautiful theory were contradicted by experiments, then the experiments were wrong. In contrast, a mathematically "ugly" theory - like Richard Feynman`s theory of quantum electrodynamics - could not possibly be correct even though it agreed well with experiment. As Helge Kragh explains, Dirac even developed an unorthodox theory of the cosmos in which Newton`s gravitational constant decreased slowly with time - dismissing the lack of experimental evidence as of no decisive importance. (p. 27)
Contact: Helge Kragh, Aarhus University, Denmark (tel. +45 89 42 3505; fax +45 89 42 2047; e-mail ivhhk@ifa.au.dk)

Behind the fa'§ade of the Nobel Prize
When great theoretical physicists like Dirac, Heisenberg, Pauli and Schrödinger were rewriting the laws of physics in the mid-1920s, it seemed obvious to most outsiders that their achievements should be immediately rewarded with a Nobel Prize. However, the physics committee of the Swedish Academy of Sciences thought otherwise. Robert Marc Friedman, who has had access to the Nobel archives, explains that the committee`s refusal lay squarely at the feet of one member: Carl Wilhelm Oseen. Arrogant and offensive, Oseen had a very narrow view of what constituted a scientific discovery. The impasse was only broken when Dirac`s prediction of antimatter proved correct, although it led the prizes being awarded in a quirky and less than fair fashion. (p. 33)
Contact: Robert Marc Friedman, Department of History, University of Oslo, Norway (tel. +47 2285 4205; fax +47 2249 3761; e-mail robert.friedman@hi.uio.no)

Solid questions for quantum computers
Quantum computers have been touted as a revolutionary technology that could perform calculations far faster than conventional computers and enable otherwise intractable problems to be solved. But building a working quantum computer may be impossible, warns Robert Keyes of IBM`s research division. Such a computer would require thousands of identical quantum bits or "qubits": tiny devices that can be in either of two quantum states or in both at the same time. "It will be hard to make a large number of such devices that are sufficiently alike to meet the rigorous demands of quantum computing," says Keyes. "Many physicists have not fully appreciated that these problems may limit - or even prevent altogether - a collection of qubits from working as a quantum computer. (p. 15)
Contact: Robert W Keyes, IBM Almaden Research Center, New York, US (tel. +1 914 945 2141 ; fax +1 914 945 2040; e-mail rkeyes@us.ibm.com)

Also in this issue:
Neutrino factories: aiming for the big time (p. 5)
Element 118: a case of misconduct (p. 7)
India builds energy amplifier (p. 12)
Dirty bombs spark war of words (p. 17)
Tuning in to the early universe (p. 21)
Nanotubes speed up (p. 22)
Molecular simulations break the ice (p. 25)
Between a rock and a hard place (p. 56)

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