The hunt for extra-terrestrial existence has been taking place around the world since the 1960s.The main technology involved for the search is by using radio telescopes. The primary objective is to search for signals coming from other civilizations who are residing in other planets. Radio telescopes can detect waves. The wavelengths are of low energy radio spectrum. It uses the principle of the electromagnetic spectrum. These low energy waves are emitted by stars and planets which are surrounding the planetary motion. The radio part of the spectrum is known as the water hole. In radio spectrum process, the emission of wavelength from Galaxy and Earth atmosphere is the minimum.
As a result, there is the emission of wavelength from hydrogen (H) and Hydroxyl (OH). This hydrogen (H) and hydroxyl ions (OH) react together to produce water (H+OH) which is referred to as water hole. Few telescopes are used from earth to locate the extra-terrestrial life. The Arecibo telescope is developed in Puerto Rico and the Parkes Telescope is developed in South Wales. Australia was invented for the search of extra-terrestrial species. Arecibo telescopes used 305-meter width large disks. The Recent invention involves the use of Allen Telescope (Mills, Grant and Verdet, 2007). This telescope was proposed as a joint venture between SETI (Search For Extra-Terrestrial Institute) and the University of California which is located in Berkeley. This Telescope involves the radio emission of stars involved in planetary motion. The benefit of Allen telescope is that it is used to see many stars one at a time where previous telescopes were limited in observing a single star at a time. The advantage of using Allen Telescope is that it uses small bowl-shaped disks which are quite portable. These disks are linked with one another. These disks can be enlarged by adding more disks conveniently in the telescope. The Allen disks contain antennas which can detect wavelength. These antennas can detect radio waves frequencies under the range of 1000 to 10000 megahertz.