Arecibo and the Great Silence – Where We Talk About a Parrot Named Alex

An aerial photograph showing the Arecibo Observatory telescope, with a picture of Alex at the forefront. The dish reflector of the telescope is built into a valley in the landscape, and the feed antenna is suspended by cables above it. Since the reflector can't be moved, the telescope is steered to point at different regions of the sky by moving the feed antenna $ ($in bell shaped dome$ )$ along on a curving track. The dome shields the feed antenna from interfering radio signals. Collage: NaturPhilosophieArecibo – What a Dish!

The Arecibo observatory is a very large radio telescope located in Puerto Rico.  In 1974, astronomers used it to broadcast a message into outer space intended to demonstrate human intelligence.  Why are we so interested in finding intelligence in the stars, and yet so deaf to the many species who manifest it here on Earth?

The Arecibo observatory‘s 305-metre (1,000-foot) radio telescope is used in three major areas of research: radio astronomy, radar astronomy and atmospheric science.  Scientists who want to use the telescope can submit research proposals that are evaluated by an independent scientific board.

From its construction in the 1960s until 2011, the observatory was managed by Cornell University.

At the time of its completion in 1963, Arecibo was the largest single-aperture telescope on Earth.  It remained so until recently, in July 2016.

The observatory gained more recognition in 1999, when it began collecting data for the SETI@home project.


An Ear to the Universe

A close up photograph of the feed antenna of the Arecibo Radio Telescope, at Arecibo in Puerto Rico. The triangular platform at the top is fixed, and the azimuth arm rotates beneath it.  To the left is the Gregorian sub-reflector, and to the right is the 29-metre $ ($96-foot$ )$ long line feed tuned to 430 MHz.  Just visible at the upper right is part of the rectangular waveguide that brings the 2.5 MW 430 MHz radar transmitter's signal up to the focal region. Source: Wikipedia
A detailed view of the beam-steering mechanism and some antennas of the Arecibo radio telescope.  Image: Alessandro Cai

Arecibo is both a radio receiver and a radio transmitter.

It is an ear for listening, and a mouth for speaking.

The dish surface is made of 38,778 perforated aluminium panels, each one about 1 by 2 m (3 by 6 feet), supported by a mesh of steel cables.  

Radio waves consists of electromagnetic waves that are sent through the atmosphere.

Radio transmitters and receivers can be tuned to broadcast or receive radio waves at precise frequencies.

The observatory has four radar transmitters, with effective isotropic radiated powers of

  • 20 TW (continuous) at 2380 MHz,

  • 2.5 TW (pulse peak) at 430 MHz,

  • 300 MW at 47 MHz, and

  • 6 MW at 8 MHz.


Arecibo’s reflector is a spherical reflector.  To aim the device, the receiver is moved to intercept signals reflected from different directions by the spherical dish surface of 270 m (870 ft) radius.

The receiver is on a 900-ton platform suspended 150 m (492 ft) above the dish by 18 cables running from three reinforced concrete towers, one 111 m (365 ft) high and the other two 81 m (265 ft) high, placing their tops at the same elevation.  The platform has a rotating, bow-shaped track 93 m (305 ft) long, called the azimuth arm, carrying the receiving antennas and secondary and tertiary reflectors.  This allows the telescope to observe any region of the sky in a forty-degree cone of visibility about the local zenith (between −1 and 38 degrees of declination).

Puerto Rico’s location near the Northern Tropic allows the Arecibo telescope to view the planets in the Solar System over the Northern half of their orbit.

You cannot see radio waves or hear them, but radio receivers can pick them up and convert them to sounds, images, or data.

In 1974, we humans sent a message – an interstellar communiqué, if you will – aimed at Messier 13, a globular cluster of stars, about 21,000 light-years away.

Its content was determined by astrophysicist and Search for Extra-Terrestrial Intelligence (SETI) founder Frank Drake, and visionary Carl Sagan.


The Drake Equation

A photograph of Frank Drake, posing in front of his equation written on a white board.
Frank Drake is an American astrophysicist, most notable as one of the pioneers in the search for alien intelligence, and the creator of the Arecibo Message – a digital encoding of an astronomical and biological description of the Earth and its lifeforms for transmission into the cosmos.  Source: SETI Institute

Frank Drake is most notable as one of the pioneers in the search for extraterrestrial intelligence, including the founding of SETI.  He mounted the first observational attempts at detecting extraterrestrial communications in 1960 in Project Ozma, and developed his famous equation.

The Drake equation is a probabilistic argument used to arrive at an estimate of the number of active, communicative extraterrestrial civilisations in the Milky Way galaxy.  The number of such civilisations, N, is assumed to be equal to the mathematical product of

(i) the average rate of star formation, R*, in our galaxy,

(ii) the fraction of formed stars, fp, that have planets,

(iii) the average number of planets per star, ne, that can potentially support life,

(iv) the fraction of those planets, fl, that actually develop life,

(v) the fraction of planets bearing life on which intelligent, civilised life, fi, has developed,

(vi) the fraction of these civilisations that have developed communications, fc, i.e., technologies that release detectable signs into space, and

(vii) the length of time, L, over which such civilisations release detectable signals, for a combined expression of:

N=R^{\ast} \cdot f_p \cdot n_e \cdot f_l \cdot f_i \cdot f_c \cdot L

Within the limits of our existing technology, any practical search for distant intelligent life must necessarily be a search for some manifestation of a distant technology.  After about 50 years, the Drake equation is still of seminal importance because it is a ‘road map‘ of what we need to learn in order to solve this fundamental existential question.


The Message: An Interstellar Communiqué

A graphical representation of the message sent at Arecibo, including the following information: The numbers one to 10. The atomic numbers for carbon, hydrogen, oxygen, nitrogen, and phosphorus. A very basic representation of the DNA double helix. The formulas for the sugars and bases in DNA nucleotides. A blocky image of a human. Earth’s position in the Solar system - with Pluto still shown as a planet, a matter that is still up for debate. An image of the Arecibo telescope that resembles the Gmail logo.
The Arecibo message that was sent in 1974.  Source: SETI

The most powerful broadcast ever deliberately beamed into space was made from Puerto Rico in 1974, as part of the ceremonies held to mark a major upgrade to the Arecibo radio telescope.

The radio transmission consisted of a simple, pictorial message, aimed at our putative cosmic companions in the globular star cluster Messier 13 (M13) – the Great Globular Cluster in Hercules.  This stellar cluster contains approximately a third of a million stars, and its centre of its core is located roughly 25,000 light-years from Earth, near the outer edge of our galaxy, the Milky Way.

The Arecibo message is a digital encoding of an astronomical and biological description of the Earth and its lifeforms.  The radio transmission lasted less than three minutes.

The broadcasted message used a string of 1,679 binary digits.  It contained approximately 210 bytes of data, transmitted at a frequency of 2,380 MHz, and modulated by shifting the frequency by 10 Hz, with a power of 1,000 kW.

The idea behind it was that the alien civilisation who would receive the message could recognise 1,679 as a semi-prime number and multiple of 23 and 73.  When the ones and zeroes of the binary-coded message are put into grid form, the result is a pixelated summary of humanity.

It contains several parts:

  • The numbers one to 10.

  • The atomic numbers for carbon, hydrogen, oxygen, nitrogen, and phosphorus.

  • A very basic representation of the DNA double helix.

  • The formulas for the sugars and bases in DNA nucleotides.

  • A blocky image of a human.

  • Earth’s position in the Solar system – with Pluto still shown as a planet, a matter that is still up for debate.

  • An image of the Arecibo telescope that resembles the Gmail logo.


A stellar map pinpointing the location of the M13 cluster in the constellation of Hercules.
Stellar Location of Messier 13 Globular Cluster.

Since it will take nearly 25,000 years to reach its intended destination, the Arecibo message is viewed as a demonstration of human technological achievement, as opposed to a real attempt to enter into a conversation with extraterrestrials. 

Obviously, the core of the star cluster, to which the message was aimed, will have moved through space during the transit time, and it will no longer be in the same location by the time the message arrives.  However, the proper motion of M13 is small enough that the cluster will only move 24 light years, only a small fraction of the diameter of the whole cluster.


The Fermi Paradox

The idea that we represent the only intelligence in the Universe seems preposterous.  However, despite the increasing range of our extraterrestrial search, we have found only silence.

In 1950, physicist Enrico Fermi argued that, given a number of assumptions, the Earth should already have been visited by aliens.

Fermi’s Paradox is the apparent contradiction between the lack of evidence and the seemingly high probability estimates for the existence of extraterrestrial civilisations.

Fermi noted the probability of Earth-like planets existing somewhere in the Universe, and the probability of life having arisen on them, the likelihood for intelligent societies to have developed sophisticated technology and  the capability for interstellar travel, and their duration span.

Eventually, he concluded from these possibilities that we ought to have been visited long ago, and many times over, by extraterrestrial species.  However, as he noted no convincing evidence for this, Fermi was lead to ask: “Where is everybody?”

This is the great silence.


The Om symbol.The Sound of Creation


In Hinduism, Om is one of the most important spiritual symbols.  It refers to the soul, the self within, and to the ultimate reality, the entirety of the Universe, the truth, the divine, the supreme spirit, the cosmic principles, the knowledge.

According to Hindu myths, the Universe was created with a sound: “Om” – a syllable that contains within it everything that ever was, and everything that ever will be.

When Arecibo points at interstellar space, it does hear a faint hum.  This is the oldest light in the Cosmos, the residual radiation from the Big Bang – the original explosion that created the Universe fourteen billion years ago.  Astronomers call it the Cosmic Microwave Background or CMB.

You could think of the CMB as a barely audible reverberation – the original “Om”, a syllable so resonant that the night sky will keep on vibrating with it for as long as the Universe exists.

But mostly, there is silence.  A great silence.


A photograph of physicist Enrico Fermi posing in front of a blackboard.
Enrico Fermi (1901-1954) at the University of Chicago. Source: Atomic Heritage Foundation

Many attempts have been made to explain the Fermi paradox.  Primarily, these suggested either that intelligent extraterrestrial life is extremely rare, or proposed reasons why such civilisations have not contacted or visited Earth:

  • Extra-terrestrial life is rare or non-existent

  • No other intelligent species have arisen elsewhere in the Universe

  • Intelligent alien species lack advanced technology

  • It is the nature of intelligent life to destroy itself

  • It is the nature of intelligent life to destroy others

  • Periodic extinction by natural events

  • Resource depletion and climate change

  • Inflation hypothesis and the youngness argument

  • Intelligent civilisations are too far apart in space or time

  • It is too expensive to spread physically throughout the Galaxy

  • Human beings have not existed long enough

  • Civilisations broadcast detectable radio signals only for a brief period of time

  • They tend to isolate themselves

  • They are too alien

  • Everyone is listening, no one is transmitting

  • Earth is deliberately not contacted

  • Earth is purposely isolated – the Planetarium Hypothesis

  • It is dangerous to communicate

  • They are already here undetected

  • They are here unacknowledged

  • Human beings are NOT listening properly


So what if instead of searching for intelligent life forms in far away galaxies, we simply began to listen to the World around us…?


Taxonomy of Life: Us and Them

This picture shows the frontispiece of Borges's Book of Imaginary Beings and his fictitious taxonomy, taken from an ancient Chinese encyclopædia entitled Celestial Emporium of Benevolent Knowledge: those that belong to the Emperor, embalmed ones, those that are trained, suckling pigs, mermaids, fabulous ones, stray dogs, those included in the present classification, those that tremble as if they were mad, innumerable ones, those drawn with a very fine camelhair brush, others, those that have just broken a flower vase, those that from a long way off look like flies.
Jorge Luis Borges’s fictitious taxonomy, taken from an ancient Chinese encyclopaedia entitled Celestial Emporium of Benevolent Knowledge.

The way we think about animals is fundamental to how we understand ourselves and our place in the World.  The idea of a “natural order” in the living world has become embedded in our society.

The differences and similarities we perceive between human and non-human animals have been the subject of enquiry since the ancient Greek philosophers.  The notion of a hierarchical structure was later reinforced by religious scriptures with a divine explanation.

But it was not until the 18th century that we began to seek scientific explanation.

Taxonomy – the naming, describing and classifying of organisms – proposed a system for objectively ordering and ranking the animal kingdom.  Today, its legacy underpins almost every aspect of our daily lives.

One of the first scientific attempts to record, describe and rank the animal kingdom was made by Swedish physician and botanist Carl Linnaeus, in his 1735 publication Systema Naturae.  For the first time, humans were classed as animals.

Linnaeus described our species with the words Nosce te ipsum, reasoning that our very ability to recognise ourselves as human was essentially what set us apart from non-human animals.  He devised the first standardised two-part naming system for all lifeforms, which has been in use ever since.

“If you do not know the names of things, the knowledge of them is lost too.”  (Philosophia Botanica)


Wildlife documentaries, natural history museums and zoos create representations of Nature that frame our ideas about animals.  Whether through carefully edited film footage, realistic displays of preserved specimens or the dramatic staging of living animals, they arrange the natural world.

What we see, and how we encounter it, has a significant effect on our behaviour towards animals.  With the rapid loss of habitats and species threatening the health of our planet, the historical roots of our beliefs about animals are now coming under closer scrutiny.

Is the separation of humans from other animals, both in our minds and our environments, compatible with creating a sustainable World?

An artistic photograph of a man an a chimp, sitting back to back. From "Anima" collection, published 1984.
“The Old Man and The Ape”  Photograph: James Balog.

Darwin’s writings On The Origin of Species persuaded the World that the difference between different species of animals and plants is not in fact the fixed immutable difference that it appears to be.

The doctrine of natural kinds, which had rendered classification easy and definite, which was enshrined in the Aristotelian tradition and protected by its supposed necessity for orthodox dogma, was suddenly swept away forever out of the biological world.

The difference between man and the lower animals, which to our conceited human minds appears enormous, was shown to be a gradual achievement involving intermediate being who could not with any certainty be placed either within or without the human species – the mere process of genetic evolution.

From that moment on, old familiar landmarks became wavering and indistinct.  Sharp outlines felt increasingly blurred.  Things and species lost their boundaries.  No one could say for certain where they began or ended.

And more importantly, why do we demand that, as proof of intelligence, non-human animals communicate to us in human language, only to dismiss the creatures that actually do so?


Humans and Parrots

A photograph of Professor Irene Pepperberg and Alex.
Professor Irene Pepperberg, with Alex: Even though Pepperberg eventually began teaching other parrots in her lab, none of them seemed to match Alex in terms of intellect or language acquisition. Source: Daily Mail

Humans have lived alongside parrots for thousands of years, and only recently have they considered the possibility that parrots might be intelligent.

For 30 years, Dr Irene Pepperberg studied Alex, an African grey parrot.  Before Pepperberg worked with Alex, it was widely believed by scientists that a large primate brain was needed to handle complex and abstract problems related to language and understanding.

Birds were not considered intelligent, as their only perceived use of communication involved mimicking and repeating sounds in their interactions.

However, this idea was overturned.  Alex’s accomplishments were such that they supported the idea that birds may be able to reason on a basic level and use words creatively.  Alex’s intelligence was put on a par to that of dolphins and great apes.

Prof. Pepperberg reported that Alex appeared to show the intelligence of a five-year-old human child, and that he was yet to reach his full potential by the time he died.  She also believed that the bird possessed the emotional level of a human two-year-old.


Smart Alex

Listing Alex’s accomplishments in 1999, Irene Pepperberg said he could identify 50 objects and recognise quantities up to six.  Alex the parrot could distinguish seven colours and five shapes, and understand a variety of concepts such as:

  • “bigger”,

  • “smaller”,

  • “same” and

  • “different”.


Alex had a vocabulary of over 100 words, and he appeared to have an understanding of what he said.

When he was tired of being tested, Alex would say “Wanna go back“, meaning that he wanted to go back to his cage.  Although he was not trained to say where he wanted to go, he seemingly picked it up from being asked where he would like to be taken.

Alex had even worked out for himself that saying “I’m sorry…” is associated with defusing a tense, angry and potentially dangerous moment.

In July 2005, Pepperberg reported that Alex understood the concept of nothing or zero.

A year later, she discovered that Alex’s perception of optical illusions was similar to that of human perception.


Alex died in 2007, aged 31.  His last words were:

“You be good.  I love you.”

Parrots are vocal learners.  Human beings are too.

I speak, therefore I am.


Sometimes it is hard to make sense of a behaviour that is so different from our own.  As human beings, we think parrots are mindlessly mimicking our words.  Perhaps parrots think human beings are not very bright at all…

While we go to great technological lengths to seek intelligent life throughout the Universe, perhaps we should not forget to look much closer to home.  Why aren’t we more interested in listening to the voices of our fellow creatures?

We must observe.  We must also listen.