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    Invisibility Cloak, true or not?

    16:56 02 October 2007

    • NewScientist.com news service
    • Colin Barras

    The world’s first true invisibility cloak – a device able to hide an object in the visible spectrum – has been created by physicists in the US. But don’t expect it to compete with stage magic tricks. So far it only works in two dimensions and on a tiny scale.

    The new cloak, which is just 10 micrometres in diameter, guides rays of light around an object inside and releases them on the other side. The light waves appear to have moved in a straight line, so the cloak – and any object inside – appear invisible.

    The cloak was built by a team led by Igor Smolyaninov at the University of Maryland, and borrows some ideas from the first theoretical design for an invisibility cloak, published by Vladimir Shalaev from Purdue University, West Lafayette, Indiana, US, earlier this year.

    Their breakthrough comes just a year after US and British physicists created an invisibility cloak that worked in the microwave region of the electromagnetic spectrum. At that time, a visible light cloak was thought to be years away because of the much shorter wavelengths produced in the visible spectrum.

    "At optical frequencies, [wavelengths] get very tiny, and the range of properties available from materials is limited," says John Pendry, a physicist at Imperial College London, and a member of the team that produced the microwave invisibility cloak.

     

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    We have broken speed of light. Maybe not.

    A pair of German physicists claim to have broken the speed of light - an achievement that would undermine our entire understanding of space and time.

    According to Einstein’s special theory of relativity, it would require an infinite amount of energy to propel an object at more than 186,000 miles per second.

    However, Dr Gunter Nimtz and Dr Alfons Stahlhofen, of the University of Koblenz, say they may have breached a key tenet of that theory.

    The pair say they have conducted an experiment in which microwave photons - energetic packets of light - travelled "instantaneously" between a pair of prisms

    that had been moved up to 3ft apart.

    Being able to travel faster than the speed of light would lead to a wide variety of bizarre consequences.

    For instance, an astronaut moving faster than it would theoretically arrive at a destination before leaving.

    The scientists were investigating a phenomenon called quantum tunnelling, which allows sub-atomic particles to break apparently unbreakable laws.

    Dr Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of."

    By Nic Fleming, Science Correspondent

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