1st intentional signal to space sent by Arecibo

Signal to space: Many small figures made up of little squares.
On November 16, 1974, the Arecibo Observatory beamed the 1st intentional signal to space. Image via Wikimedia Commons. Click here for an explanation of each part of the message.

1st intentional signal to space in 1974

On November 16, 1974, astronomers used the Arecibo telescope in Puerto Rico to beam out the most powerful broadcast ever deliberately sent to space. They said the goal was to contact alien life. And some applauded it, but others didn’t. On the plus side, it reminded people that Earth likely isn’t the only planet in the Milky Way where intelligent life has evolved. But others felt – if alien civilizations do exist out there – we shouldn’t call attention to ourselves.

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The message in our signal to space

Designed by Cornell astronomy professor Frank Drake with input from other scientists including Carl Sagan. So, the final result was a simple and elegant broadcast. Basically, it consisted of a pattern of binary numbers. This message contained information about the basic chemicals of life and the structure of DNA. Plus, it included Earth’s place in our solar system and even a stick figure of a human.

Large dish in the ground with 3 towers and cables leading to receiver above middle of dish.
Arecibo radio telescope in Puerto Rico, used in 1974 to broadcast the 1st intentional radio signal into space. Image via Wikimedia Commons.

Sending the Arecibo message

By the way, it took three minutes to send 1,679 bits of information, a snail’s pace compared to modern computer modems. And according to the SETI Institute:

The broadcast was particularly powerful because it used Arecibo’s megawatt transmitter attached to its 1,000 feet (305 meter) antenna. The latter concentrates the transmitter energy by beaming it into a very small patch of sky. The emission was equivalent to a 20 trillion-watt omnidirectional broadcast, and would be detectable by a SETI experiment just about anywhere in the galaxy, assuming a receiving antenna similar in size to Arecibo’s.

In fact, the 1974 signal went out in the direction of M13, a globular star cluster orbiting the center of our Milky Way galaxy. Basically, it was chosen because it’s a large collection of stars and was available in the sky at the time and place of the ceremony.

Also, globular star clusters are very far away. For instance, M13 is about 25,000 light-years from Earth.

As a matter of fact, the 1974 signal is now 48 light-years away from us.

Bottom line: The first intentional radio signal to space was to contact alien life. In fact, the Arecibo radio telescope in Puerto Rico beamed the signal outward on November 16, 1974. What do you think? Should we be advertising our presence in space?

November 16, 2022

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Deborah Byrd

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