Google Doodle highlights the first attempt to phone ET

Mankind sent its first radio message to the stars 44 years ago -- and we're still waiting to hear back.

The Arecibo message, consisting of basic information about the human race and Earth, was sent on Nov. 16, 1974, from the Arecibo radio telescope in Puerto Rico. The message was sent to demonstrate the capabilities of the recently upgraded telescope's 1,000-foot-diameter dish antenna.

Transmitted at a frequency of 2380MHz, the message consisted of 1,679 binary bits representing ones and zeros arranged in a grid 73 rows by 23 columns. To mark the anniversary of the message's dispatch, Google designed a Doodle that mimics the message's composition. (The Doodle is destined to appear in many parts of the world, including Puerto Rico, but not the mainland US, Google says.)

Written with the help of astronomer Carl Sagan, the resulting pictograph (at right) contained representations of fundamental chemicals of life, human DNA, a crude diagram of our solar system indicating Earth's position in it, simple pictures of a human-like figure and images of the Arecibo telescope itself.

The message was devised by a team of researchers led by Frank Drake, then a professor of astronomy at Cornell University. Drake, heavily involved in the search for extraterrestrial intelligence, developed the Drake equation in 1961 to estimate the number of planets in the Milky Way galaxy capable of hosting extraterrestrial life.

"It was strictly a symbolic event, to show that we could do it," Donald Campbell, a professor of astronomy at Cornell University, said in a statement in 1999. Campbell was a research associate at the Arecibo Observatory when the message was sent.

Some criticized the transmission as dangerous, worrying it might attract the attention of hostile aliens. They probably needn't have worried, as it's a long shot that the message might ever be read by extraterrestrial intelligence.

The message was sent only once over a narrow beam directed toward a group of 300,000 stars in the constellation Hercules known as M13. And don't hold your breath waiting for a response. Traveling at the speed of light, the message will take 25,000 years to reach its intended destination -- and another 25,000 years for us to hear back.

Also, the star cluster targeted by the message will have moved out of the way as part of the galaxy's normal rotation by the time the message arrives. But the message will continue on its path through space, reaching distant galaxies in millions of years.

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Doodling our world: Check out Google's previous celebrations of people, events and holidays that impact our lives.