The Cosmic Chorus
The Universe is full of noises — and Earth now also contributes to the cacophony. The first time we called out to the stars was on November 19, 1962 with The Morse Message. This message was sent in Morse code from the Evpatoria Planetary Radar to Venus. What did we say? "MIR" — the Russian word for both world and peace. This was followed a few days later on November 24 by "LENIN" and "SSSR" (Russia's leader and the abbreviation for the Soviet Union, respectively). Later, in 1999, a team headed by Alexander Zaitsev, a rogue Search for Extraterrestrial Intelligence (SETI) member, beamed Cosmic Call 1 to four nearby suns from the Yevpatoria RT-70 radio telescope in Crimea. He called his system Messaging to Extraterrestrial Intelligence (METI).
He argued that his decision was due to the SETI Paradox, which he characterized as "This paradoxical disparity of effort, a passionate desire to receive and no corresponding attempt to give." He also stated that he did "not want to live in a cocoon, in a 'one-man island.'"
Similar messages were subsequently sent out in 2001 (Teen Age Message), 2003 (Cosmic Call 2), and 2008 (A Message From Earth). These messages caused fierce debate within the scientific coommunity, prompting multiple meetings by the Royal Society in 2010 on the topic of "Towards a Scientific and Societal Agenda on Extraterrestrial Life."
SETI has sent authorized messages into the cosmos, including the Lone Signal in 2013 and A Simple Response to an Elemental Message in 2016. Other messages not related to or verified by SETI have also been sent, such as the the Hello From Earth message in 2009.
In response, we have heard very little back, causing some to dub the universe "The Great Silence" — David Brin told Phys.org that the most obvious possibilities have now been ruled out, "including gaudy tutorial beacons that advanced ETCs would supposedly erect."
A particularly exciting narrowband radio signal from space was detected by the Ohio State University's Big Ear radio telescope in 1977, which many have since dubbed the Wow! Signal, although it has now been shown to probably be caused by comets. A less notable example is Radio source SHGb02+14a, which was detected in 2003. The radio source was 1420 MHz and lasted for a minute each time it was observed, although the signal was extremely weak.
How do we Speak to Aliens?
There are two aspects of our communication with aliens: how we send it, and what we say. There has been vigorous discussion about both facets of inter-galaxy communication.
The main means we currently have of broadcasting ourselves across the universe is through radio signals. Frequency modulated radio waves were used when we projected a message from the Arecibo radio telescope in Puerto Rico in 1974: it contained, in binary, pictorial representations of humanity, formulas for the elements and compounds that make up DNA, as well as representations of the Solar System. Other systems have been more manual: for example, the Pioneer 10 and 11 probes bolting 'Pioneer Plaques' to their doors.
Future efforts will try to update this system, using either the more sophisticated radio signals we possess today, or turning to lasers to beam ourselves to other planets. METI will begin their search by beaming to Proxima Centauri, the nearest star to our sun.
Douglas Vakoch, the former director of Interstellar Message Composition at the SETI Institute and president of METI, said to Forbes, "It’s too late to conceal ourselves in the universe, so we should decide how we want to represent ourselves." But how can we know how what we choose to represent is what will be received when we have no comprehension of the technology aliens may be using, or of their specific culture?
The central debate over what we send to aliens stems from what they would think if they received a signal. Opinion is split among scientific heavyweights over whether aliens would be benevolent or malevolent. Carl Sagan believes that any contact would be benign because, as he stated in his novel Contact, written in 1985, “In the long run, the aggressive civilizations destroy themselves, almost always.” On the other hand, Stephen Hawking believes that "if aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans."
Other specialists such as Seth Shostak, an astronomer at SETI, think that if we truly believed in a threat, we would be more careful about all radio use; he told phys.org, "We cannot pretend that our present level of activity with respect to broadcasting or radar usage is 'safe.' If danger exists, we're already vulnerable."
An encounter with aliens is a real possibility, and one that would have earth-changing consequences. When we will meet them is anyone's guess — it may be in ten years, it may be never — but it is important to have discussion surrounding how to deal with an encounter to prepare for every possible outcome.