Shape of things to come (or perhaps not) Government examines, then dismisses, threat of gravitational waves

Published 19 December 2008

A U.S. company solicited funds from the Defense Intelligence Agency to examine the threat to the United States from gravitational waves; the agency concludes that notions that these waves might pose a security threat “belong to the realm of pseudo-science, not science” (physicists say you did not need a 40-page report to reach this conclusion)

The U.S. Defense Intelligence Agency (DIA) has commissioned a report to explore whether gravitational waves could pose a threat to U.S. security. The JASON Defense Advisory Group was also asked to determine whether high-frequency gravitational waves could offer an image the center of the Earth, or be used for telecommunications.

New Scientist’s David Robson writes that gravitational waves are ripples in space-time caused by the movement of an extremely large mass, such as a very dense star. Even waves from huge stellar events, however, have been too weak to trip the most sensitive detectors. The best evidence is indirect, coming from observations of how superdense, binary neutron stars lose energy. Still, the JASON team was asked to consider a funding proposal from U.S. company GravWave to the DIA that claimed humans could generate strong gravitational waves on Earth, using the Gertsenshtein effect (which describes how electromagnetic waves traveling through a very strong magnetic field can be converted into gravitational waves).

Physicists engaged in the effort to detect gravitational waves said they were surprised the DIA took the company’s proposal seriously — and expressed surprise that a committee took a 40-page report to come to that conclusion. “The proposal is utter nonsense,” says Karsten Danzmann from the Max Planck Institute for Gravitational Physics in Hanover, Germany, and member of the GEO600 project to detect gravitational waves. “I’m a bit surprised the agency bothered to commission an investigation — it would probably have been enough to just ask an in-house science adviser,” he says.

David Shoemaker from MIT, a member of the LIGO project to detect gravitational waves, agrees that a quick phone call to a physicist may have been sufficient (he noted that the U.S. Department of Defense “always have a few projects on the go that disobey the rules of thermodynamics”).

Back to the JASON group’s report. The report found that the gravitational waves technique is so inefficient that it would take longer than the lifetime of the universe for every power station on Earth to produce a gravitational wave with the energy of one ten-millionth of a Joule. Accelerating a spacecraft at 10 meters per second squared, a rate that just exceeds the pull of Earth’s gravity, would require 1025 times (a 1 followed by 25 zeroes) the electricity output of the world. The report concludes: “These proposals belong to the realm of pseudo-science, not science.”