The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other planets.Scientific investigation began shortly after the advent of radio in the early 1900s, and focused international efforts have been ongoing since the 1980s. In 2015, Stephen Hawking and Russian billionaire Yuri Milner announced a project called Breakthrough Listen.



The Ohio State University Radio Observatory was a Kraus-type (after its inventor John D. Kraus) radio telescope located on the grounds of the Perkins Observatory at Ohio Wesleyan University in Delaware, Ohio from 1963 to 1998. Known as Big Ear, the observatory was part of Ohio State University's Search for Extraterrestrial Intelligence (SETI) project. The telescope was designed by John D. Kraus. Construction of the Big Ear began in 1956 and was completed in 1961, and it was finally turned on for the first time in 1963.

The main reflector of Big Ear—The Flat Reflector—measured approximately 103 meters by 33 meters, giving it the sensitivity equivalent to a circular dish measuring nearly 53 meters in diameter.The observatory completed the Ohio Sky Survey in 1971, and from 1973–1995, Big Ear was used to search for extraterrestrial radio signals, making it the longest running SETI project in history. In 1977, the Big Ear received the Wow! signal. The observatory was disassembled in 1998 when developers purchased the site from the university and used the land to expand a nearby golf course.