What is the Gertsenshtein effect

Nonsense idea: US agency examines danger from artificial gravitational waves

Some science fiction authors have already propelled their spaceships with artificially generated gravitational waves. Anyone who thinks that such ideas belong exactly there - namely in the realm of fantasy - is in good company: Any astrophysicist would flatly reject this idea in view of current and foreseeable technical developments.

However, the US defense intelligence service DIA sees it quite differently. The current scientific approach to the subject did not stop the Defense Intelligence Agency from commissioning a study to determine whether human-generated gravitational waves could pose a threat to the security of the United States. In addition, the JASON Defense Advisory Group, a group of scientists who advise the US government on technological matters, should find out whether the elusive waves could also be used for long-distance communication.

Gravitational waves are disruptions in space-time, caused by the movement of an extremely large mass, such as a particularly dense star. But here, too, the waves generated are not enough to cause even the most sensitive sensors to deflect. The best indications of gravitational waves are still obtained indirectly, for example when observing superdense double neutron stars.

Gertsenshtein effect

Nevertheless, the JASON team was commissioned to take a closer look at a financing application from GravWave to DIA. The paper claims that strong gravitational waves could be produced artificially here on earth using the Gertsenshtein effect.

With the effect mentioned, electromagnetic waves that are sent through a particularly strong magnetic field actually create gravitational waves. When the scientists of the JASON team calculated the method mathematically, the supporters of such a technology were probably not very enthusiastic about the results: All power plants on earth would need longer than the lifespan of the universe in order to ultimately generate a gravitational wave with an energy of just once one ten millionth of a joule.

If you wanted to drive a spaceship with this force, which can just leave the force of gravity, you would do 1025 Times the amount of electricity produced worldwide. Unsurprisingly, the study comes to the conclusion: "The proposal belongs in the realm of pseudoscience."

"Absolute Nonsense"

Scientists dedicated to studying gravitational waves are surprised that it took a 40-page report to come to this conclusion. "The idea is absolute nonsense," says Karsten Danzmann from the Max Planck Institute for Gravitational Physics in Hanover. "I'm a little baffled that the agency commissioned a study for this. It would probably have been enough to ask a scientific advisor in-house," says the physicist.

MIT researcher David Shoemaker also explains that a quick phone call to any physicist would have been enough to dismiss GravWave's suggestions as nonsense. Nevertheless, he points out that the financing of studies to check the usefulness of current projects is generally good. "The Department of Defense always has a few projects going on that violate the principles of thermodynamics. I wish they'd look into that."

In the mid-1990s, for example, the Pentagon invested millions of dollars in a multi-year project to develop a quasi-nuclear weapon called the hafnium bomb. As it eventually turned out, the research on this was based on scientific nonsense. Seen in this light, the money for the JASON group to refute the gravitational wave idea was probably money well invested. (red)