Directed energy weapons such as lasers and particle beams, (either ground-based or space-based, having sufficient power to damage satellites or their sensors).

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It is quite possible that technologies being developed for other purposes (such as lasers, which are useful for all sorts of advanced materials processing) will make the process cheaper and easier still.

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Observatories such as GEO 600 bounce lasers down long tunnels, hoping to pick up the fantastically small disturbances the waves should generate as they pass through the Earth.

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After all, it was the Pentagon that gave an early boost to computers during World War Two, and then helped spawn innovations such as jet engines, lasers and digital networking in the postwar period.

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Ultra powerful lasers, such as Hiper, have been proposed as one method for reaching these extreme conditions, although many remain sceptical about the technique.

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During the Cold War, it poured billions of dollars into the development of new technologies such as jet engines, nuclear power and lasers.

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Some firms that sell lasers for resurfacing, such as Israel's Lumenis and America's Candela, have now entered the photorejuvenation business using newer laser technologies to remove wrinkles by stimulating the skin to produce collagen.

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