The Dozen Times Humans Have Tried to Communicate With Extraterrestrials

The question of whether intelligent life exists elsewhere in the universe has intrigued humanity for centuries. As our technological capabilities advance, our quest to find an answer to this profound question intensifies. While we have not yet discovered definitive evidence of extraterrestrial intelligence, several scientific, philosophical, and technological considerations suggest that the possibility is worth serious contemplation.

Since the 1960s, there has been an ongoing scientific effort to detect signals from advanced civilizations. Under the “Search for Extraterrestrial Intelligence” (SETI), researchers use radio telescopes to scan the sky for unusual signals that could indicate intelligent origin. In addition to radio signals, scientists are also considering the search for technosignatures—indicators of advanced technology such as megastructures (e.g., Dyson spheres), atmospheric pollutants, or unusual energy emissions. The discovery of such signatures would provide compelling evidence of intelligent extraterrestrial life.

Aside from monitoring the night sky for possible extraterrestrial signals, researchers have also tried to send messages to intelligent extraterrestrial life. This is known as Active SETI or METI (Messaging to Extra-Terrestrial Intelligence).

Here are some of the attempts that have been so far:

Morse Message

The Morse Message was one of the first radio signals intended specifically for interstellar intelligence. It consisted of a three words—MIR (meaning both “peace” and “world” in Russian), LENIN and USSR—encoded in Morse code and sent towards the planet Venus in 1962. The messages were transmitted from the newly built Evpatoria Planetary Radar (EPR) complex in Crimea.

The message was sent in two parts. The first message “MIR” was transmitted on November 19, 1962, and the second messages consisting of LENIN and USSR was transmitted on November 24, 1962. Both signals reflected off the surface of Venus and were received back on Earth in approximately 4 and a half minutes. Given the location of Venus in November 1962, the message is even now speeding across the cosmos towards the Libra constellation.

Pioneer plaques

Mounted outside the body of the Pioneer 10 and Pioneer 11 spacecrafts are a pair of gold-anodized aluminum plaques featuring a pictorial message. The plaques show the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft. These include a schematic representation of the hyperfine transition of hydrogen, which is the most abundant element in the universe; a pulsar map with the sun at the center, showing the relative distances of 14 pulsars and the binary code of their periods, which can help date the launch era; the silhouette of the Pioneer spacecraft is shown behind the figure of the human beings so their scale cane be deduced by measuring the spacecraft; and a sketch of our solar system with a long arrow indicating the Earth as the planet that launched the spacecraft.

Pioneer 10 was launched in 1972. It flew past Jupiter in 1973, crossed the orbit of Saturn in 1976, the orbit of Uranus in 1979 and in 1983, the craft crossed the orbit of Neptune. The last successful contact with the craft was made in 2002 when Pioneer 10 was 12 billion km (80 AU) from Earth. It is currently heading in the direction of Aldebaran (65 light years away) in the constellation of Taurus.

Pioneer 11 was launched in 1973, flew past Jupiter in 1974 and Saturn in 1979. The probe lost all power and had to shutdown in 1995 and contact was lost. At that time it approximately 111 AU away. The spacecraft is now heading toward the constellation of Aquila. It is expected to pass near one of the stars in the constellation in about 4 million years.

Arecibo message

The Arecibo message was beamed out into space from the Arecibo Telescope in Puerto Rico on 16 November 1974. The message consisted of several characters and graphics coded in binary, and was aimed at the current location of M13, about 25,000 light years from Earth. Assuming the aliens could correctly decode it, the 1,679 bits of data would reveal:

• The numbers one to ten.
• The atomic numbers of the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus, which make up DNA.
• The formulas for the chemical compounds that make up the nucleotides of DNA.
• The estimated number of DNA nucleotides in the human genome, and a graphic of the double helix structure of DNA.
• The dimension of an average man, a graphic figure of a human being, and the human population of Earth which was about 4 billion at the time.
• A graphic of the Solar System (including Pluto), indicating which of the planets the message is coming from.
• A graphic of the Arecibo radio telescope and the dimension of the transmitting antenna dish.

The Arecibo message with color added to highlight its separate parts. 

Voyager Golden Records

When Voyager 1 and 2 were launched in 1977, each carried an identical phonograph record containing a rich collection of sounds and images selected to portray the diversity of life and culture on Earth. These records were intended for any intelligent extraterrestrial life form who may find them. The Golden Record contains 116 images portraying a variety of objects from the solar system, to plants and animals, portraits of people and architecture. They also contain audio recordings of spoken greetings in 55 ancient and modern languages, and other human sounds, like footsteps and laughter. In addition, the record contains musical compositions of Bach, Mozart, Beethoven and many more. Also included is a cover that gives a quick pictorial explanation of how to play the record and read the images.

The Voyager spacecraft with the Golden Record attached to its side.

Voyager 1 passed the orbit of Pluto in 1990, and left the Solar System in 2004. In about 40,000 years, it and Voyager 2 will each come to within about 1.8 light-years of two separate stars: Voyager 1 will have approached star Gliese 445, located in the constellation Camelopardalis, and Voyager 2 will have approached star Ross 248, located in the constellation of Andromeda.

Cosmic Call

In 1999 and again in 2003, two sets of interstellar radio messages were sent from Yevpatoria, Ukraine, towards nine star systems. The message consist of special symbols created to represent various basic data, such as the alphabets, various mathematical operators and signs, different units of measurement, the names of the planets, chemical elements, physical concepts, biological concepts and so on. The messages were transmitted multiple times. The nearest star targeted is the Gliese 49 in the northern constellation of Cassiopeia. It is 32 light years away from earth. The furthest star where this message is intended is 16 Cygni, a triple star system located approximately 69 light-years away from Earth in the constellation of Cygnus. 16 Cygni is known to contain an extrasolar planet.

Teen Age Message

Between Cosmic Call 1 and Cosmic Call 2, the Yevpatoria Planetary Radar sent another series of interstellar radio transmissions to six solar-type stars during August–September 2001. The transmission is called Teen Age Message because the message's content and target stars were selected by a group of teens from four Russian cities, who collaborated in person and via the Internet. Each transmission comprised three sections: a sounding, a live theremin concert, and digital data including images and text. The digital data included the logotype of TAM, written greetings in Russian and English, and artistic drawings. This section and the concert program were composed by teens from different parts of Russia.

A Message from Earth

A Message from Earth (AMFE) was transmitted on 9 October 2008 towards Gliese 581c, an exoplanet orbiting within the Gliese 581 system at a distance of 20.5 lightyears. The signal is a digital time capsule containing 501 messages that were selected through a competition on the social networking site Bebo. More than half a million people including celebrities and politicians participated in the AMFE project. The message was sent using the RT-70 radar telescope of Ukraine's State Space Agency. The signal will reach the planet Gliese 581c in early 2029.

Across the Universe

On 4 February 2008, NASA Deep Space Network's (DSN) Madrid Deep Space Communication Complex, located in Robledo, near Madrid, Spain, transmitted the song "Across the Universe" by the Beatles towards the star Polaris. The transmission was rather a publicity stunt than a serious attempt to communicate with extra-terrestrial life.

A. L. Zaitsev, part of the Teen Age Message project, argues that the compressed digital format used by NASA makes the data more fragile to errors compared to TAM's analogue approach, not to mention aliens would not have knowledge on human audio compression algorithms. The transmission data rate is also too high to allow for a remote radio station to faithfully receive. Finally, the choice of Polaris also makes the message unlikely to reach any alien lifeform should they exist.

Hello From Earth

In 2009, the COSMOS magazine collected goodwill messages from the public through an online form and transmitted them towards the Gliese 581d exoplanet on Friday 28 August 2009 using the NASA/CSIRO Canberra Deep Space Communication Complex at Tidbinbilla, Australia. The signal is expected to reach the intended target around December 2029.

Wow! Signal Reply

On August 15, 1977, the Ohio State University's Big Ear radio telescope in the United States received a strong signal from the direction of the constellation Sagittarius. The transmission was received at frequency 1420 megahertz, which is naturally emitted by hydrogen, the most common element in the universe. It had been speculated decades before that any technologically advanced civilizations will likely use this frequency for communication. Because the radio signal was 30 times more powerful than the average radiation from deep space, a volunteer astronomer named Jerry Ehman who was watching the telescope data scrawled "Wow!" on a computer printout, leading to the signal's moniker.

The Wow! signal.

On August 15, 2012, exactly 35 years after the event, a project directed by the National Geographic Channel and Arecibo Observatory beamed a package of digital information out to the heavens containing Twitter messages from the public, as well as videos from celebrities such as Stephen Colbert, Jorge Garcia, and Leila Lopes, the 2011 Miss Universe.

Lone Signal

The Lone Signal project was founded by businessman Pierre Fabre with the intention of sending interstellar messages from Earth to a possible extraterrestrial civilization. On June 17, 2013, it transmitted short, 144-character messages by citizens of Earth to the red dwarf star Gliese 526, located 17.6 light-years away from Earth in the constellation Boötes. The Lone Signal team hoped to construct a network of satellite dishes across the Earth's surface, which could beam messages to many regions of the Milky Way galaxy. However, lack of funding caused the project to cease transmission.

A Simple Response to an Elemental Message

A Simple Response to an Elemental Message was another casual attempt at interstellar communication that was made on 10 October 2016 by the European Space Agency Cebreros (DSA2) deep-space tracking station. The message consisted of 3775 worldwide responses to this initiative's posed question; "How will our present, environmental interactions shape the future?". The transmission was made towards Polaris.

Projects like "Across the Universe," "Hello From Earth," and "A Simple Response to an Elemental Message" are not always taken seriously. The first two were transmitted to Polaris, a supergiant star 431 light-years away. Even if Polaris has a planetary system, it may not support life due to the star's young age of 70 million years. Additionally, the high transmission rates of around 128 kbit/s, combined with moderate transmitter power (about 18 kW), made these messages prone to interference.

The debate over whether to contact extraterrestrials is a significant topic in space ethics and policy. Physicist Stephen Hawking, in his book "A Brief History of Time," argued that alerting extraterrestrial intelligences to our presence is risky, pointing to humanity's own history of harsh encounters between civilizations with technological disparities. In contrast, astronomers like Seth Shostak and Jill Tarter believe that any advanced extraterrestrials capable of interstellar communication and travel would likely have developed a cooperative and peaceful intelligence. However, Tarter feels that it is premature for humans to engage in active SETI and suggests that we should focus on advancing our technology while continuing to listen for signals.