Revealing technology

Watching a picture of Earth at night, we will see the world seem to be shining. Based on that fact, scientists are beginning to look for signs of advanced extraterrestrial civilizations by radiating light, through the technology commonly used to collect energy from a star or even a galaxy.

In 1960, American mathematician and theoretical physicist Freeman Dyson was the first to propose the idea that advanced civilizations beyond Earth could develop technology that encompasses a star and harvests. Most of its power, a structure called "Dyson sphere" . If these celestial bodies really exist, astronomers can detect the heat they emit by using space observation telescopes with infrared light.

"The key is finding aliens who don't want to communicate (with us) . They definitely have to emit waste heat. The only way to do that is to radiate a lot of infrared radiation." , Mr. Dyson said.

Currently, astronomers at the University of Pennsylvania (USA) are beginning to narrow the study of Dyson spheres. However, according to Dyson, the new study is in its infancy and may take hundreds of years.

New method of hunting alien intelligence

Much of the search for extraterrestrial intelligence (SETI) is focused on listening to radio signals sent by some strange civilization, as described in the science fiction movie "Contact" . However, this approach assumes that aliens want to communicate with people. The Dyson spheres can overcome the disadvantages of this approach, because even an unconventional civilization dealing with the outside will emit waste heat.

Russian astrophysicist Nikolai Kardashev has classified long-standing civilizations into three categories: civilizations that control the resources of a planet (type I) and a star (type II), or of a galaxy (type III). A Dyson sphere represents Type II civilization.

Part of the movie "Star Trek: The Next Generation" portrays the non-Enterprise ship responding to an emergency signal from a crashed transport ship. outer shell of a Dyson sphere. Even so, Dyson himself has never imagined the structure as a solid solid sphere.

"It is ultimately not a ball as we know it, but just anywhere random aliens generate a lot of energy," Dyson said and described his structure as a "artificial biosphere" , possibly a cloud of objects orbiting a star close enough to absorb all starlight. According to him, a solid solid sphere would be too weak to help its weight against a star's gravity.

Dyson estimates that an extraterrestrial civilization with a surface temperature of about 27 degrees C will emit infrared radiation at a wavelength of about 10 microns (1 micron = 1 / 1,000,000m). The Earth's atmosphere emits a lot of radiation in this area, so a space-based telescope will work best. However, when Dyson proposed the idea, the necessary technology was not available.

Efforts to find Dyson spheres

Then, in 1983, a group of international scientists released the Infrared Astronomical Satellite (IRAS), the first observatory to record the entire sky with infrared light. They discovered that in the space is full of infrared sources, but most of them are from galactic dust and other natural sources.

Recently, Richard Carrigan, a scientist working at the Fermilab laboratory in the US, used IRAS to search for Dyson spheres. According to him, a Dyson sphere acts as a "black body" , absorbing all the electron radiation that falls on it and emitting energy depending on temperature. A black body looks like cosmic dust in infrared light, but there are differences in spectrum.

Carrigan measured infrared spectra with IRAS spectroscopy, but only detected a few objects within a few hundred light-years of Earth, probably Dyson spheres. (A light year is about 9.5 trillion km). The expert and colleagues also used the Allen Institute's Allen antenna network to hunt for radio signals emitted from those objects, but nothing was gained.

What if alien civilizations have developed Dyson spheres that suck the energy of an entire galaxy? Carrigan tried to search for such galaxies - Dyson spheres because it was the most easily detected object. Jason Wright, astrophysicist at the University of Pennsylvania (USA), is doing the same thing with the WISE space telescope of the US Aerospace Agency.

If astronomers find signs of Dyson spheres or any other extraterrestrial technology, it will trigger a global effort to observe them with different astronomical devices. At that time, even if the research world did not detect alien civilizations, the search could bring new, interesting physical discoveries.