Welcome back to our Fermi Paradox series, where we take a look at possible resolutions to Enrico Fermi’s famous question, “Where Is Everybody?” Today, we examine the possibility that we haven’t heard from any aliens is because no one is transmitting!

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?”

This became the basis of the Fermi Paradox, which refers to the disparity between high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. Since Fermi’s time, there have been several proposed resolutions to his question, including the possibility that everyone is listening, but no one is broadcasting – otherwise known as the “SETI-Paradox.”

This theory comes down to the noticeable divide between what is referred to as “passive SETI” and “active SETI,” the latter of which is more commonly known today as Messaging Extraterrestrial Intelligence (METI). These differences in approach have become the focal point of attention in recent years as the two have become more differentiated, and the latter has become more common.


Passive SETI, which is generally characterized by listening to space for signs of radio communications (or other discernible technosignatures), accounts for the vast majority of SETI measures to date. This includes what is arguably the first example of an extraterrestrial radio search, which was performed by Nikola Tesla in 1899 while conducting experiments at his Colorado Springs laboratory.

On this occasion, Tesla believed he had detected an extraterrestrial radio signal because of the way it ceased as soon as Mars set in the night sky. Further analysis proved inconclusive, and explanations included radio interference from a neighboring experimental station, a misreading of the results, and background noise caused by Jupiter’s moon Io passing through its magnetic field.

The first modern SETI experiment, which took place in 1960, was also passive by definition. This was Project Ozma, a survey led by Cornell astronomer Frank Drake that relied on the 26-meter (85-foot) radio telescope at the Green Bank Observatory in West Virginia. The project examined the nearby stars Tau Ceti and Epsilon Eridani for signs of radio transmissions in a 400-kilohertz band around the 1.420 gigahertz marker frequency.

In fact, the concept of METI as being distinct from SETI is a relatively recent development. Russian scientist Alexander Zaitsev coined the term METI in a 2006 paper of the same name. As Zaitsev emphasized:

“The science known as SETI deals with searching for messages from aliens. METI science deals with the creation of messages to aliens. Thus, SETI and METI proponents have quite different perspectives. SETI scientists are in a position to address only the local question ‘does Active SETI make sense?’

“In other words, would it be reasonable, for SETI success, to transmit with the object of attracting ETI’s attention? In contrast to Active SETI, METI pursues not a local and lucrative impulse, but a more global and unselfish one – to overcome the Great Silence in the Universe, bringing to our extraterrestrial neighbors the long-expected annunciation ‘You are not alone!’”

History of METI

Meanwhile, the first attempt to send a message was directed at Venus in 1962 by scientists from the Evpatoria Planetary Radar (EPR) center in Crimea. This was known as The Morse Message, which consisted of a radio transmission sent in Morse Code – the letters M-I-R (Mir, the Russian word for “peace”) followed by “Lenin” and “SSSR.” In 1974, the most powerful (and most famous) broadcast was beamed to space from the Arecibo Observatory in Puerto Rico.

This was known as the Arecibo Message, a 1679 bit transmission arranged into 73 lines (23 characters per line) of binary code. The message consisted of simple images of the Arecibo telescope, the Solar System, DNA, a stick figure of a human, and some of the biochemicals of earthly life. The message was aimed at the globular star cluster M13, located roughly 21,000 light-years from Earth, near the edge of the Milky Way galaxy,

Between 1999 and 2003, three transmissions (Cosmic Call 1, Teen Age Message, and Cosmic Call 2) were all made from the Evpatoria Planetary Radar (EPR) center in Crimea to various nearby stars. Whereas Cosmic Calls consisted of code denoting the alphabet, numbers, periodic table, and scientific concepts, the Teen Age Message consisted of a coherent sounding signal, an analog message encoded in Theremin
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