An interstellar message is one which seeks to contact putative communicating intelligences outside the solar system. The concept is based on the notion that in a universe as large as the one we inhabit, there ought to be other communicating intelligences apart from us out there. The idea of sending out messages to our interstellar neighbours came to life with the advent of the Search for Extraterrestrial Intelligence, SETI, in the 1960s. Searching, as we were, for evidence of extraterrestrial communicating intelligence by means of deliberate or accidental messages sent out by them and intercepted by us, it made perfect sense that we, in turn, should send out messages of our own to such folk, in the hope that they would one day receive them.
The first interstellar message sent from earth was the message broadcast from the radio telescope at the Arecibo Observatory in Puerto Rico on November 16 1974. The message, a one time broadcast, was made up of 1679 binary digits, some 210 bytes in size broadcast towards the globular star cluster M13. 1679 digits were used because it is the product of two prime numbers, 73 and 23, and it was arranged in a rectangle of 73 rows by 23 columns. The contents were created by SETI pioneer, Frank Drake with assistance from the late Carl Sagan. Arranged as a rectangle of 23 rows and 73 columns, the digits produce just a jumbled mess.
The Arecibo message included seven parts. The first part set out the numbers one to ten. The second part set out the atomic numbers of the elements hydrogen, nitrogen, oxygen, carbon and phosphorus which together make up deoxyribonucleic acid, DNA. The third part sets out the formulae of the sugars and bases which make up the nucleotides of DNA. The fourth part set out the number of nucleotides in DNA and provides a pictorial representation of the double helix form of DNA. The fifth part presents another pictorial representation of the human form and the average size of a man as well as the population of the planet at the time the message was sent. The sixth part of the message presents a pictorial representation of the solar system and earth's position therein. Finally, the seventh part of the message shows a pictorial of the radio telescope at Arecibo, from which the message was transmitted, as well as its physical dimensions. The entire transmission time was about 3 minutes.
Cosmic Call 1 and 2 were transmitted in 1999 and 2003 respectively from the Evpatoria Planetary Radar of the National Space Agency of Ukraine which is located on the Crimean Peninsula. The effort was coordinated by Richard Braastad of Team Encounter, a Texas based company, and Dr. Alexander Zaitsev of the Russian Academy of Sciences. The transmissions, directed at nine stars in seven constellations, with expected delivery dates ranging from 2036 to 2069. The contents included an interstellar "Rosetta Stone", named for the famous stone found near Rosetta, Egypt, in 1799 which helped scholars decipher Egyptian hieroglyphics, composed by two Canadian scientists, Yvan Dutil and Stephane Dumas. The Rosetta Stone, a multi-page bitmap image, built up a vocabulary starting from basic maths and moving on to progressively more complex ideas such as the physical properties of elements like hydrogen. The messages also included a copy of the Arecibo broadcast, as well as text video, audio and music files which were compiled from submissions from around the world.
The Teen Age message, transmitted in 2001, was also sent from the Crimean radio facility and coordinated by Dr. Zaitsev. It included scientific information designed to assist any recipients decode the Teen Age message, as well as messages compiled from submissions from teens from all over Russia. The message was sent to six nearby stars in six constellations, with expected arrival dates at the respective destinations ranging from 2047 to 2070.
Apart from radio transmissions, physical copy has also been sent out for possible communication with extraterrestrial intelligences, albeit as part of some other project rather than as a direct attempt to communicate with putative extraterrestrials. The 2 Pioneer probes of 1972 and 1973, Pioneer 10 and Pioneer 11, which are expected to rendezvous in Taurus and Aquila constellations in two and four million years respectively, had on board plaques showing the position of earth and the solar system, pictorial representations of the human form and a representation of the transition of the hydrogen atom. Similarly, the 2 Voyager probes of 1977, each had on board a golden record carrying pictures and sounds of earth, data regarding our location in space, as well as symbolic instructions as to how to play back the record.