6/23/1974 1st extraterrestrial message sent from Earth into space
Arecibo message
This is the message with color added to highlight its separate parts. The actual binary transmission carried no color information.
The
Arecibo message is a 1974
interstellar radio message carrying basic information about humanity and Earth sent to
globular star cluster M13 in the hope that
extraterrestrial intelligence might receive and decipher it. The message was
broadcast into space a single time via
frequency modulated radio waves at a ceremony to mark the remodeling of the
Arecibo radio telescope in
Puerto Rico on 16 November 1974. The message was aimed at the current location of M13 some 25,000
light years away because M13 was a large and close collection of stars that was available in the sky at the time and place of the ceremony. The message consisted of 1,679
binary digits, approximately 210
bytes, transmitted at a frequency of 2,380
MHz and modulated by shifting the frequency by 10 Hz, with a power of 450
kW. The "ones" and "zeros" were transmitted by frequency shifting at the rate of 10 bits per second. The total broadcast was less than three minutes.
The number 1,679 was chosen because it is a
semiprime (the product of two
prime numbers), to be
arranged rectangularly as 73 rows by 23 columns.
The alternative arrangement, 23 rows by 73 columns, produces an unintelligible set of characters (as do all other X/Y formats). The message forms the image shown here when translated into graphics, characters, and spaces.
Dr.
Frank Drake, then at
Cornell University and creator of the
Drake equation, wrote the message with help from
Carl Sagan, among others. The message consists of seven parts that encode the following (from the top down):
- The numbers one (1) to ten (10) (white)
- The atomic numbers of the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus, which make up deoxyribonucleic acid (DNA) (purple)
- The formulas for the sugars and bases in the nucleotides of DNA (green)
- The number of nucleotides in DNA, and a graphic of the double helix structure of DNA (white & blue)
- A graphic figure of a human, the dimension (physical height) of an average man, and the human population of Earth (red, blue/white, & white respectively)
- A graphic of the Solar System indicating which of the planets the message is coming from (yellow)
- A graphic of the Arecibo radio telescope and the dimension (the physical diameter) of the transmitting antenna dish (purple, white, & blue)
Since it will take nearly 25,000 years for the message to reach its intended destination (and an additional 25,000 years for any reply), the Arecibo message is viewed as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials. In fact, the core of M13, to which the message was aimed, will no longer be in that location when the message arrives. However, as the
proper motion of M13 is small, the message will still arrive near the center of the cluster. According to the
Cornell News press release of November 12, 1999, the real purpose of the message was not to make contact but to demonstrate the capabilities of newly installed equipment.