NEWS OF THE WEEK PHYSICS High-Tech Materials Could Render Objects Invisible No, this isn’t the 1 April issue of The invisibility isn’t perfect: It works only in a Science, and yes, you read the head- narrow range of wavelengths. line correctly. Materials already The authors map out the necessary speed being developed could funnel light variations and leave it to others to design the and electromagnetic radiation materials that will produce them. But around any object and render it researchers already know how to design meta- invisible, theoretical physicists pre- materials to achieve such bizarre properties, at dict online in Science this week least for radio waves, says Nader Engheta, an (www.sciencemag.org/cgi/ electrical engineer at the University of Penn- content/abstract/1125907 and … sylvania. “It’s not necessarily easy, but the 1126493). In the near future, such recipes are there,” says Engheta, who last year cloaking devices might shield sen- proposed using a metamaterial coating to sitive equipment from disruptive counteract an object’s ability to redirect light, radio waves or electric and mag- making combination nearly transparent. netic fields. Cloaks that hide objects Cloaking devices for radio waves could from prying eyes might not be much appear within 5 years, Gbur says, and cloaks further off, researchers say. for visible light are conceivable. Pendry notes The papers are “visionary,” that even a cloak for static fields would, for says George Eleftheriades, an No see? Forget the Invisible Man’s transparency potion; new example, let technicians insert sensitive elec- electrical engineer at the Univer- materials might ferry light around an object, making it invisible. tronic equipment into a magnetic resonance sity of Toronto in Canada. “It’s imaging machine without disturbing the pioneering work that sets the stage for future toward the inner surface of the shell. In fact, machine’s precisely tuned magnetic field. on June 30, 2009 research.” Greg Gbur, a theoretical physicist along the inner surface, light must travel infi- Alas, even if invisibility proves possible, it at the University of North Carolina, Charlotte, nitely fast. That doesn’t violate Einstein’s the- may not work the way it does in the movies. notes that others have studied invisibility but ory of relativity because within a material, For example, a cloaking device would be use- says the new papers describe more precisely light has two speeds: the one at which the rip- less for spying, Pendry says. “Nobody can see how to achieve it. “Each gives specific exam- ples in a wave of a given frequency zip along, you in there, but of course you can’t see them, ples of how you might design an invisibility and the one at which energy and information either.” Keeping track of your always-invisible device,” he says. flow. Only the second must remain slower than device might be a pain, too. From spaceships that vanish in Star Trek light in a vacuum, as it does in a metamaterial. –ADRIAN CHO movies to Harry Potter hiding beneath his www.sciencemag.org imperceptible cloak, invisibility has been a U.S. COURTS mainstay of science fiction and fantasy. But it might become a reality thanks to emerging ‘Disappointed’ Butler Exhausts Appeals “metamaterials,” assemblages of tiny rods, c-shaped metallic rings, etc., that respond to Thomas Butler’s legal journey has come to an fraud involving fees for clinical trials he had electromagnetic fields in new and highly end. On 15 May, the U.S. Supreme Court conducted at Texas Tech. Last fall, a three- controllable ways. John Pendry of Imperial declined to take up the case of the physician judge panel on the U.S. Court of Appeals for College London and colleagues, and Ulf and microbiologist who received a 2-year the Fifth Circuit upheld his conviction (Science, Downloaded from Leonhardt of the University of St. Andrews, prison sentence for shipping plague samples 4 November 2005, p. 758); the full appeals U.K., independently calculated how the to Tanzania without the required permits and court declined to review the case. properties of a shell metamaterial must be for defrauding his employer, Texas Tech Uni- “I have never in my career seen someone tailored to usher light around an object versity in Lubbock (Science, 19 December who was handed such a gross injustice,” says inside it. An observer would see whatever is 2003, p. 2054). his attorney, George Washington University behind the object as if the thing weren’t Butler declined to be interviewed, but his law professor Jonathan Turley. Turley says that there, Leonhardt says. wife Elizabeth says her husband is “very dis- the fraud charges, which the government The theorists exploit the fact that light is appointed.” Butler is working in Lubbock at a added after Butler refused to accept a plea bar- always in a hurry, taking the quickest route job unrelated to his professional training, she gain, concerned a dispute between the between two points. That’s not always a says, and weighing offers to rebuild his career. researcher and his employer that would not straight line, because light travels at different “This has been a tremendous blow,” she adds, otherwise have been prosecuted criminally. speeds in different materials, and it opts for “but we are healing little by little.” Butler, 64, was transferred to a halfway the path that minimizes the total time of In January 2003, Butler reported vials con- house in November after having served transit. So when light passes from, say, air taining the plague bacterium Yersinia pestis 19 months of his sentence and came home in into glass, its path may bend, which is why missing from his lab; after questioning by the late December. His supporters, including ordinary lenses focus light. FBI, he signed a statement, which he later chemistry Nobelist Peter Agre of Duke Uni- Pendry and colleagues and Leonhardt cal- withdrew, saying he had accidentally versity in Durham, North Carolina, are hop- culated how the speed of light would have to destroyed the samples. In his trial, the jury dis- ing against hope for a presidential pardon, if vary from point to point within a spherical or missed all but one of the government’s charges not from George W. Bush then possibly from cylindrical shell to make the light flow around relating to illegal shipping and handling of his successor. the hole in the middle. Light must travel faster plague samples but found Butler guilty of –MARTIN ENSERINK BROS./CANAL PLUS/REGENCY/ALCOR/THE KOBAL COLLECTION WARNER CREDIT: 1120 26 MAY 2006 VOL 312 SCIENCE www.sciencemag.org Published by AAAS REPORTS than in the rest of the disk. The correlation values as a measure of the goodness of fit for structure of the Perseus and Carina arms past remains notable even if we do not apply a each curve. In this scheme, arms with values R , 20 kpc is suggestive of this behavior. thickness filter to the data or if we use another of y and f0 that trace overdense regions will definition of the thickness (3, 11). The two maps naturally have a large median and thus a large References and Notes are not independent, however; changing the goodness of fit. The best fit values of y and 1. H. C. van de Hulst, C. A. Muller, J. H. Oort, Bull. Astron. Inst. Neth. 12, 117 (1954). density distribution in the arms will necessarily f0 for each of the four arms are given (Table produce changes in the measured thickness unless 1). Other fits that connect a different set of 2. F. Kerr, G. Westerhout, in Galactic Structure, vol. 5 of Stars and Stellar Systems, A. Blaauw, M. Schmidt, Eds. the perturbations are distributed in the same way features in the map could be drawn, because (Univ. Chicago Press, Chicago, IL, 1965), pp. 167–202. as the initial distribution. The alignment of assigning a unique arm pattern to a map is not 3. A. P. Henderson, P. D. Jackson, F. J. Kerr, Astrophys. J. overdensities with regions of reduced thickness possible. We find pitch angles for the outer 263, 116 (1982). was suggested previously (3). This alignment has arms in the range from 20- to 25-; this is larger 4. D. Malin, Am. Astron. Soc. Photo Bull. 16, 10 (1977). , - 5. P. M. W. Kalberla et al., Astron. Astrophys. 440, 775 (2005). not been observed in other galaxies because than the value of y 13 averaged over a 6. D. Hartmann, W. B. Burton, Atlas of Galactic Neutral surface density maps are most easily made for variety of tracers (20). This does not neces- Hydrogen (Cambridge Univ. Press, Cambridge, 1997). face-on galaxies where there is no information sarily imply a disagreement, however, be- 7. E. Bajaja et al., Astron. Astrophys. 440, 767 (2005). about the thickness of the gas layer. cause the arms could be unwinding in their 8. E. M. Arnal, E. Bajaja, J. J. Larrarte, R. Morras, W. G. L. The radial profile of the HI disk has been a outer regions. Po¨ppel, Astron. Astrophys. Suppl. Ser. 142, 35 (2000). 9. M. J. Reid, Annu. Rev. Astron. Astrophys. 31,345 matter of controversy for many years. A sharp Various models of the locations of the (1993). falloff in HI emission as a function of velocity arms have been proposed. We compared our 10. R. P. Olling, M. R. Merrifield, Mon. Not. R. 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