SETI Project - Search for Extraterrestrial Intelligence

The SETI research is based on the assumption that extraterrestrial civilizations exist in space and related communications systems and communications technologies are used, as on Earth. So far it is not known whether extraterrestrial life exists, or whether there are other technological civilizations that are transmitting and receiving signals in the interstellar position. Besides the search for radio signals to operate the search for signals in the visible and near infrared region, (Optical SETI) or shortly called Ossetia. It is believed that extraterrestrials very powerful laser could use to communicate over interstellar distances. When visible light is the amount of mirror or lens size, you need to ensure that the radiation emitted by a given divergence angle (half angle of an imaginary radiation cone, inside which the majority of the radiation) which is smaller than at the longer wavelength radio waves. Although this reduces the probability of detecting a non-intentional on the ground directed beam, but the strength increases near the beam center for a given output power. The search for these optical signals is achieved with high-resolution spectrograph,  trying to find a very narrow spectral lines.