Quote from Philip Morrison where he describes the origins of the paper that he co-wrote with Giuseppe Cocconi: ***"Cocconi came to me one day — I’ve often reported this — and said, "You know what, Phil? If there are people out there, won’t they communicate with gamma rays that'll cross the whole galaxy?" And I said, “Gee, I know nothing about that. They will cross the galaxy. It’s very thin in hydrogen. But not all that well. There will be some loss." "What about radio?" he said. "I don’t know much about radio, but I understand there is a lot of radio out there. Why not use radio? It’s much cheaper. You get many more photons per watt and that must be what counts." And we began working on that..."*** The hydrogen line - **1420.40575 MHz** - is the precession frequency of neutral hydrogen atoms. Hydrogen atoms are the most abundant substance in space and they're chirping away at 1420 MHz create a powerful signal, which is easily detected small radio telescopes. This frequency happens to fall in the quietest part of the radio spectrum known as the Microwave Window. Freeman Dyson describing the proposal by Cocconi-Morrison. **Freeman Dyson - Communication with aliens: The Cocconi-Morrison conjecture** [](https://www.youtube.com/watch?v=uvbuppH1RPI) Giuseppe Cocconi was an Italian physicist who was director of the Proton Synchrotron at CERN in Geneva. His research interests include atomic particle interactions, cosmic rays and radio astronomy. He is well known for his work that lead to the creation of SETI - search for extraterrestrial intelligence. You can learn more here: [Giuseppe Cocconi](https://en.wikipedia.org/wiki/Giuseppe_Cocconi)  > ***"Few will deny the profound importance, practical and philosophical, which the detection of interstellar communications would have. We therefore feel that a discriminating search for signals deserves a considerable effort. The probability of success is difficult to estimate; but if we never search the chance of success is zero."*** This is the central question of this paper. If a society becomes developed enough what communication channel would they create in order to identify other similarly intelligent societies? >***"The lifetime of such societies is not known; but it seems unwarranted to deny that among such societies some might maintain themselves for times very long compared to the time of human history, perhaps for times comparable with geological time. It follows, then, that near some star rather like the Sun there are civilizations with scientific interests and with technical possibilities much greater than those now available to us."*** Philip Morrison was a professor of physics at the Massachusetts Institute of Technology. He is known for his work on the Manhattan Project during World War II, and for his later work in quantum physics, nuclear physics high energy astrophysics, and SETI - search for extraterrestrial intelligence. You can learn more here: [Philip Morrison](https://en.wikipedia.org/wiki/Philip_Morrison)  G. Cocconi and P. Morrison set forward one of the first proposals for detecting extraterrestrial life. This is the seminal paper that initiated the age of Electromagnetic search for extraterrestrial life which became a component of the modern [SETI](https://www.seti.org) program. > ***"Cocconi came to me one day — I’ve often reported this — and said, "You know what, Phil? If there are people out there, won’t they communicate with gamma rays that'll cross the whole galaxy?" And I said, “Gee, I know nothing about that. They will cross the galaxy. It’s very thin in hydrogen. But not all that well. There will be some loss." "What about radio?" he said. "I don’t know much about radio, but I understand there is a lot of radio out there. Why not use radio? It’s much cheaper. You get many more photons per watt and that must be what counts." And we began working on that..."*** [SETI](https://www.seti.org) is America’s only organization wholly dedicated to searching for life in the Universe.