What is the most effective way to attract attention in a crowd of people? Simple: do something out of the ordinary the moment they look at you. This concept is at the heart of a new idea for the search for extraterrestrial civilizations, proposed by astronomer David Kipping of Columbia University in the United States.
The scientist suggests that aliens can use lasers in order to "draw" geometric shapes that will be detected by the Earth's telescope. It could work as follows. Astronomers can detect extraterrestrial civilizations using the method of transit photometry, based on observations of the passage of a planet against the background of a star. When a planet passes in front of a star, blocking out some of the light visible from Earth, the star dims slightly. To date, astronomers have discovered more than 2,300 planets using this method.
A typical transit signal is similar to a “flat bottom depression” - as the light dims, the signal descends down a gentle slope, reaches the bottom during transit, and rises upward. This means that intelligent alien scientists could announce their presence by changing the shape of the transit signal. How? For example, by directing a laser beam towards the Earth at a certain period of time, with the help of which the transit signal could be given a variety of shapes - up to the outlines of New York against the sky.
On the other hand, the same technique would allow aliens to skillfully disguise themselves from detection by humans. If at the time of the passage of a darker planet against the background of the star's disk, the aliens shine in the direction of the Earth with a laser, then they will hide their planet from the telescope. In fact, the beam of laser light will compensate for the decrease in stellar brightness, as a result of which the blinded Kepler will not notice the change and will miss the planet. According to calculations, such maneuvers do not require very large resources: lasers need about 30 megawatts of energy to keep the planet invisible in the optical range, and about 760 megawatts to "hide" in all radiation ranges.
Less powerful lasers - from 600 to 1000 kilowatts - are suitable for "removing" traces of the presence of life on the planet, such as organics or microbes. This will not interfere with its detection, but the interest in such an object among uninvited guests from space will drop significantly.