The technology for searching for alien spacecraft already exists – LIGO (2 photos)

Albert Einstein predicted the existence of gravitational waves back in 1916, but they were first detected almost a century later. In 2015, the LIGO detector detected a signal from a black hole merger, ushering in a new era in astronomy—the era of gravitational wave observations. Physicists now propose using such instruments not only to study catastrophic events in the Universe but also to search for possible traces of extraterrestrial technology.





The principle is based on a fundamental consequence of the general theory of relativity: any object with mass, when accelerated, generates gravitational waves—disturbances in spacetime that propagate at the speed of light. Typically, these waves are so weak that they can only be detected from extreme astrophysical events, such as the mergers of black holes or neutron stars.

But if a hypothetical alien civilization builds planetary-scale devices (for example, generation ships) and accelerates them to relativistic speeds, then such objects could also become sources of detectable gravitational waves.

LIGO is a Laser Interferometer Observatory. Two laser beams travel through four-kilometer-long tubes in perpendicular directions and reflect off high-precision mirrors. When a gravitational wave passes through the detector, space is slightly stretched in one direction and compressed in the other. This causes microscopic displacements of the mirrors, which are detected by the interferometer.

An international team of physicists attempted to estimate the size of an alien craft for its acceleration to be detectable using our technology. To do this, they calculated key parameters: the object's mass, acceleration rate, distance to it, and the signal strength that modern detectors would be able to detect.

The scientists dubbed these hypothetical objects RAMAcraft—a reference to Arthur C. Clarke's novel "Rendezvous with Rama," in which humanity encounters a gigantic alien object. In scientific work, this term was used to describe rapidly accelerating massive spacecraft, which could theoretically leave a trace in gravitational wave observatory data.

Calculations showed that a Jupiter-mass spacecraft accelerating to 30% the speed of light could be detected at a distance of up to 326,000 light-years—that is, anywhere in the Milky Way. An object the mass of the Moon, accelerating at the same speed, would be detected at a distance of up to 32,600 light-years.



The LIGO gravitational-wave observatory was not designed to search for alien objects, but according to research, its sensitivity is already sufficient to detect planet-scale spacecraft—if they possess a large mass and accelerate to relativistic speeds. However, extreme caution is required: a potential technosignature can easily be confused with a routine astrophysical event, and instrumental error can be mistaken for a "curious signal."

Future observatories—LISA, DECIGO, and the Big Bang Observer—as well as existing pulsar timing arrays, will be able to provide a more accurate picture. Some of these instruments could be operational as early as the 2030s. They will allow for better source characterization, verification of signals in other frequency ranges, and more reliably distinguishing potential technosignatures from natural phenomena or detector noise.

It's important to note that LIGO is not currently being used to specifically search for alien spacecraft. However, the study shows that gravitational-wave astronomy could become a new tool in the search for intelligent life in the Universe—especially for civilizations capable of building gigantic spacecraft and performing interstellar travel.