Most of the search methods for extraterrestrial civilizations are based on the detection of specific electromagnetic radiation. They are looking for characteristic changes in the luminosity of stars, either in their special spectrum or in simpler ones – radio waves that differ from natural sources. American physicists proposed expanding the range of instruments used to the detriment of gravitational wave detectors. The notorious Fermi paradox worries not only ufologists and futurologists, but also full-fledged scientists. There are many indications that life in the universe may not be a unique terrestrial phenomenon.

At the same time, until now, humanity has not found a single evidence of other intelligent civilizations. One of the hypotheses is that our tools are not good enough or configured properly to find them, so we need to create new methods. Or find new ways to use tools already in an astrophysicist’s arsenal. For example, gravitational wave observatories. The logic is as follows: if a highly developed civilization wants to travel on the scale of the galaxy, sooner or later it will build a giant or fast ship.

Maybe huge and fast at the same time. And where there is a large mass, or accelerations up to speeds of units or even tens of percent of the speed of light, fluctuations in space-time arise. What we call gravitational waves. A big advantage of gravitational wave detectors as tools to search for extraterrestrial civilizations is their field of view. Unlike optical or radio telescopes, which have an extremely narrow “field of view,” gravitational wave detectors “look” at the entire sky at once. Several physicists at leading American universities and scientific organizations have considered this idea in detail. Their detailed calculations can be found on the arXiv preprints portal.

The calculations of this work show that the most sensitive of the existing gravitational wave detectors -the LIGO, VIRGO and KAGRA terrestrial interferometers- make it possible to detect extraterrestrial spacecraft within a radius of up to one hundred kiloparsecs from Earth (326,156 light years). That is, far beyond the Milky Way, whose diameter is only 105,700 light years. It is true that alien ships should have a mass of about ten Jupiters and accelerate at 10% of the speed of light. The lower limit of detection with the available instruments is an object with a mass of about Mercury, accelerating at a comparable rate. It will already be possible to detect it in a radius of “only” 32 light years, in the vicinity of the closest stars to the Sun.

A colossal mass of fast-accelerating ships (RAMAcraft) is not a fantastic assumption. Even traveling between neighboring stars in a reasonable time requires large amounts of working fluid. Nobody canceled Newton’s laws. And if we are talking about civilizations that can colonize a significant part of the galaxy, they will probably need ships that can transport entire populations in a few generations. Alternative modes of transportation such as “warp technology” and the Alcubierre Bubble make things easier. The mass of ships built on its base will also be huge – a few or dozens of Jupiters, but the speed of movement is higher. Furthermore, the very principle of his work involves the curvature of space-time and therefore the creation of gravitational waves. Such objects must be detectable at even greater distances.