The US patent office has granted a patent on a design for an antigravity device — breaking its own resolution to reject inventions that clearly defy the laws of physics.

This is not the first such patent to be granted, but it shows that patent examiners are being duped by false science, says physicist Robert Park, watchdog of junk science at the American Physical Society in Washington DC. Park tracks US patents on impossible inventions. “The patent office is in deep trouble,” he says.

“If something doesn't work, it is rejected,” insists Alan Cohan, an adviser at the patent office's Inventors Assistance Center in Alexandria, Virginia. And when something does slip through, he says, the consequences are not significant: “It doesn't cause any problems because the patent is useless.”

But Park argues that patenting devices that so blatantly go against scientific understanding could give them undeserved respectability, and undermine the patent office's reputation. “When a patent is awarded for an idea that doesn't work, the door is opened for sham.”

Patent 6,960,975 was granted on 1 November to Boris Volfson of Huntington, Indiana. It describes a space vehicle propelled by a superconducting shield, which alters the curvature of space-time outside the craft in a way that counteracts gravity. The device builds on a claim by the Russian physicist Eugene Podkletnov that superconductors can shield the effects of gravity. NASA was at one stage investigating the idea, but it has become almost as notorious as cold fusion as an example of fringe science.

Balls up: US patent office falls for antigravity device that would allow perpetual-motion machines. Credit: J.-L. CHARMET/SPL

One of the main theoretical arguments against antigravity is that it implies the availability of unlimited energy. “If you design an antigravity machine, you've got a perpetual-motion machine,” says Park. Shield half of a wheel from gravity and it will keep turning for ever.

The US patent office has long fought to prevent applications for patents on perpetual-motion machines. In 1911, after a constant stream of applications, one commissioner ruled that they would not be considered until a working model had been running for a year. More recently, inventor Joe Newman sued the office after it rejected his application for such a device. The court finally ruled against Newman in 1990, a decision that the patent office cites in its rules about which inventions are patentable.

Unfortunately, it is not always easy to tell what the implications of a patent are. One previous patent for a device using putative “hydrinos” — shrunken hydrogen atoms — to produce huge amounts of energy was granted. It is currently being reviewed after several scientists complained that hydrinos are impossible according to the laws of physics.

Park says he sympathizes with the difficulties that patent examiners face. “Their burden has gone up enormously,” he says. “It's not surprising they get in a jam.”