Most of the methods for searching for extraterrestrial civilizations are built around the detection of specific electromagnetic radiation.
They are looking for characteristic changes in the luminosity of stars, either their special spectrum, or the simplest – radio waves that differ from natural sources. American physicists proposed to expand the range of instruments used at the expense of gravitational wave detectors.
The notorious Fermi paradox worries not only ufologists and futurologists, but also full-fledged scientists. There are too many indications that life in the universe cannot be a unique earthly phenomenon.
At the same time, until now, humanity has not met a single evidence of other intelligent civilizations. One of the hypotheses is that our tools are not good enough or not properly configured to find them, therefore, it is necessary to come up with new methods.
Or find new ways to use tools already in the arsenal of astrophysicists. 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 spaceship.
Perhaps both 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, there arise fluctuations in space-time. Which we call gravitational waves.
A huge plus of gravitational wave detectors as tools for searching 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 from leading American universities and scientific organizations have considered this idea in detail. Their detailed calculations can be found on the portal of preliminary publications (preprints) arXiv.
The calculations in this work show that the most sensitive of the existing gravitational wave detectors – ground-based interferometers LIGO , VIRGO and KAGRA – allow you to detect alien ships 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 105.7 thousand light years. True, alien ships should have a mass of about ten Jupiters and accelerate to 10% of the speed of light.
The minimum detection threshold with the available instruments is an object with a mass of approximately Mercury, accelerating to a comparable speed. It will be possible to detect it already within a radius of “only” 32 light years – in the vicinity of the stars closest to the Sun.
A colossal mass of rapidly accelerating ships ( RAMAcraft ) is not a fantastic assumption. Even traveling between neighboring stars within a reasonable amount of time requires huge 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, then they will most likely need ships that transport entire populations within a lifetime of a few generations.
Alternative modes of transportation like “warp technology” and the Alcubierre Bubble make things easier. The mass of ships built on their basis will also be huge – a few or tens of Jupiterian ones, but the speed of movement is higher.
In addition, the very principle of their work implies the curvature of space-time, and hence the creation of gravitational waves. Such objects should be detectable at even greater distances.
In addition, in the coming years, the creation of even more sensitive gravitational-wave observatories will begin – the space Big Bang Observer and DECIGO . With their help, the search efficiency will increase by an order of magnitude.
But there is a problem: you need to know what to look for. It is likely that human instruments have already recorded traces of alien ships flying across the Milky Way, we just did not distinguish them from natural sources. A whole section of the described scientific work is devoted to methods of data analysis.
It is possible that in the foreseeable future, researchers looking for extraterrestrial civilizations will have incredible amounts of data to study. If the scientific community, of course, agrees with the proposed theses. From the outside, they look more than reasonable.