The Arecibo message is a binary-encoded radio message sent into space with the intent of reaching potential extraterrestrial civilizations. It was transmitted on November 16, 1974, from the Arecibo Observatory in Puerto Rico, which was one of the world’s largest and most powerful radio telescopes at the time.

The message was designed by a team led by Frank Drake, with contributions from Carl Sagan and others. Its purpose was to demonstrate human technological capabilities and to test the ability of the Arecibo radio telescope to send a message across interstellar distances. Here’s what the message contained:

1. Basic Information: It includes information about humanity and Earth, such as the atomic numbers of hydrogen, carbon, nitrogen, oxygen, and phosphorus (the building blocks of DNA), the formulas for the sugars and bases in DNA, a graphical representation of the DNA double helix, and the human figure.
2. Solar System: It shows the position of Earth in the solar system and the relative sizes of the planets.
3. Arecibo Telescope: The message includes a depiction of the Arecibo telescope and its dish.
4. Binary Code: The message was encoded in binary (ones and zeros) and consists of 1,679 bits. This number was chosen because 1,679 is a semiprime number (the product of two prime numbers, 23 and 73), which is expected to be universally recognizable as a meaningful sequence.

The Arecibo message was sent as a demonstration rather than an attempt to communicate with any specific extraterrestrial civilization. The message will reach its target star system, M13, in about 25,000 years, though it is unlikely to be intercepted or understood by any civilizations in that region due to the vast distances involved.