SETI & CETI

SETI

SETI stands for the Search for Extraterrestrial Intelligence. It is a term to represent activities dedicated to the search for radio signals from space indicating the existence of life beyond that of Earth's. The scope has broadened since the start of optical SETI (OSETI), which looks for powerful light pulses from other star systems.

The SETI@home program

Wow signal computer output

Why it makes sense to look for signals from extraterrestial intelligence is explained by the Drake equation. However, so far nothing has been found. On Aug. 15, 1977, the so-called Wow signal was received. It is perhaps the best known "maybe".

CETI

CETI stands for Communication with Extraterrestrial Intelligence. A number of messages has been sent into space intended for intelligent for extraterrestial beings. The messages include a plaque on the Pioneer spacecraft, a record aboard the Voyager spacecraft and radio messages sent into space.

Flag of Earth

Overview of actually sent messages

Pioneer plaque (1972)

Voyager record (1977)

Arecibo radio message (1974)

Encounter radio message 2001

Encounter radio message 2003

SETI messages in literature and fiction

Sending and receiving messages from an alien civilization has been the subject of many speculations and works of fiction. In 1960, Hans Freudenthal published his "Lincos: Design of a Language for Cosmic Intercourse". It describes an artificial language, based on mathematical principles, for use in interstellar radio transmissions.

Formula in Lincos

In 1962 Frank Drake, when SETI was just getting started, suggested using numbers and pictures for communication with alien intelligence. He designed a message that he distributed to colleagues, to see if they could figure it out. He gave them a page of 551 0s and 1s. When this sequence of 0s and 1s is converted into black and white squares, and arranged in a matrix of 19 by 29 cells, you get the picture shown here to the left.

A well-known work of fiction is "Contact" by Carl Sagan (1985). The story was adapted for a movie in 1997. Harrison Brown published in 1968, together with Chloe Zerwick, "The Cassiopeia Affair". It uses a scenario very similar to "Contact". Also Fred Hoyle's "A for Andromeda " (1962) and Gunn's "The Listeners" (1972) explore the consequences of radio contact with intelligent extraterrestrials.

Jodie Foster explaining the message,
in the movie "Contact " (1997)

Message from "The Cassiopeia Affair" (1968)