Say “hello” with radios and lasers
modern science the search for extraterrestrial intelligence began in 1959 when astronomers Giuseppe Cocconi and Philip Morrison showed that radio transmissions from Earth could be detected by radio telescopes at interstellar distances. The same year, Frank Drakelaunched the first SETI search, Project Ozma, pointing a large radio telescope at two nearby Sun-like stars to see if it could detect radio signals coming from them. Following the invention of the laser in 1960, astronomers showed that visible light could also be detected from distant planets.
These first fundamental attempts to detect radio Where laser signals from another civilization were all looking for concentrated and powerful signals that were intentionally sent to the solar system and destined to be found.
Given the technological limitations of the 1960s, astronomers did not give serious thought to finding broadcast signals – like television and radio broadcasts on Earth – that would leak into space. But a beam of a radio signal, with all of its power focused towards Earth, could be detectable from much further away – just imagine the difference between a laser and a dim light bulb.
Searching for intentional radio and laser signals is still one of the most popular SETI strategies today. However, this approach guess extraterrestrial civilizations want to communicate with other technologically advanced life forms. Humans very rarely send targeted signals into space, and some researchers argue that intelligent species can deliberately avoid broadcasting their locations. This search for signals that nobody sends is called the SETI paradox.
Leaking radio waves
Although humans don’t transmit many intentional signals out to the cosmos, many of the technologies people use today produce lots of radio transmissions that leak out into space. Some of these signals would be detectable if they came from a nearby star.
The global network of TV towers constantly emits signals in many directions that leak into space and can accumulate in a detectable, although relatively small, radio signal. Research is underway to determine if current emissions from cell phone towers in radio frequency on Earth would be detectable using today’s telescopes, but the next The Square Kilometer Array radio telescope will be able to detect even weaker radio signals with 50 times the sensitivity of current radio telescope arrays.