The U.S. patent office has reportedly granted a patent for an anti-gravity device -- breaking its rule to reject inventions that defy the laws of physics.

The journal Nature said patent 6,960,975 was granted Nov. 1 to Boris Volfson of Huntington, Ind., for a space vehicle propelled by a superconducting shield that alters the curvature of space-time outside the craft in a way that counteracts gravity.

One of the main theoretical arguments against anti-gravity is that it implies the availability of unlimited energy.

"If you design an anti-gravity machine, you've got a perpetual-motion machine," Robert Park of the American Physical Society told Nature.

Park said the action shows patent examiners are being duped by false science.

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