The humans use Arecibo to look for extraterrestrial intelligence. Their desire to make a connection is so strong that they’ve created an ear capable of hearing across the universe. But I and my fellow parrots are right here. Why aren’t they interested in listening to our voices?

You’re on the Spaceship Earth […] You’d better pay your fare now You’ll be left behind You’ll be left hangin’ In the empty air You won’t be here and you won’t be there.

When imagining civilizations on other worlds, we tend to stick to the familiar. Aliens in the popular imagination are not all that different from us — they often have eyes and ears, walk on two feet, and understand the universe in roughly the same way we do.

It astonishes me how much we seem to know about aliens. They build technology-driven civilisations and pilot spaceships across the galaxy. They create energy-harvesting structures around their stars. They beam interstellar greetings to us.

Caged An out-of-this-world Cage homage, appropriated from all over the cosmos

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In 1977, NASA sent 115 images – the so-called ‘Golden Record’ – into space on board the Voyager space probe. They also included greetings in 55 different languages and a number of audio clips, including (amongst others) Beethoven’s 5th Symphony and Blind Willie Johnson’s Dark Was the Night. Projected onto a double-sided, cinema-sized screen, these images – but not the audio clips – are the basis of Steve McQueen’s solo show ‘Once Upon a Time’. The images range from photographs of children being born to family portraits, the monumental (Jupiter) to the miniature (a leaf), and the poetic (a sunset with birds) to the mechanical (a calibration circle). There are ordnance photographs of the Sinai Peninsula and an intimate portrait of a nursing mother. Ethnographic portraits, perhaps inevitably, feature too and, despite the generally auspicious and upbeat tone of the Golden Record, there are also premonitions of more immediate concerns:

In the work Once upon a Time (2004) McQueen presents a slide show of 116 of these images installed to make them seem to float in space: about two-thirds of the way to the back of a very dark room a large screen is suspended from the ceiling, but without touching the floor. The projector is behind the screen and is set to show each slide for around half a minute before dissolving it into the next. The cycle of images lasts 70 minutes and the installation includes sound.

We take it for granted that the search for extraterrestrial intelligence (SETI) is a safe endeavor. Seriously, what could possibly go wrong with passively searching for interstellar radio signals? Unfortunately, the answer is quite a lot –- especially if the incoming signal contains something malicious, like a computer virus or Trojan horse.

And according to the experts, this isn't just idle speculation – the threat is very real. So, just how concerned do we need to be? To get a better sense of this possibility, we spoke to two experts on the matter: Andrew Siemion, a PhD candidate in astronomy at SETI-Berkeley, and Milan Cirkovic, Senior Research Associate at the Astronomical Observatory of Belgrade and a leading expert on SETI.

We'll get to their answers in just a second, but it's worth doing a quick review to understand where this idea came from –- and not surprisingly, it's science fiction inspired by science.

Zona, Geoff Dyer’s recent book about Andrei Tarkovsky’s masterpiece Stalker, has been much discussed for its almost comically thorough dissection of the stately 1979 film. In an account that combines summary, memoir, meditation, tribute, and citation into a kind of deluxe version of the TV recap, Dyer sets out to convey the hypnotic effect Stalker has had on decades of viewers, and on himself. And yet, after reading the book, I was left feeling that something was missing. In both the book and the deluge of Stalker coverage its release has occasioned, perhaps the most crucial, and most popular, part of the film’s afterlife has gone entirely unremarked: the video game version.

If an alien located on a planet 100 light years from here was to switch on a big, multi-frequency radio receiver, and record all the noises coming from outer space for the next hundred years, on all frequencies, how many soap operas, advertisements and new broadcasts would they pick up from Earth? Would a mass-market radio, similar to our Earthly equivalents, pick up anything? Over time, as the number of Earth transmissions increases exponentially, would the alien pick up a cacophony or a damp fizzle? We've all heard the cliché that since the first radio broadcast, the Earth has been spewing all our bad soap operas, CB-radio call outs, airplane distress calls and re-runs of Boy Meets World into outer space. This front of radio waviness is now as many light-years from Earth, in all directions, as the number of years since it was first transmitted (or so the cliché goes).

Now, it's also a function of radio wave propogation, that the Earth's ionosphere is used to bounce some of those waves around the world. Thus people in Zimbabwe can pick up BBC World Service. So, presumably, not everything ever transmitted will have left this planet, bound for space?

So, my question is about the percentage of those waves actually are travelling out in space? As time goes on, would the increase in transmissions from Earth's past begin to overwhelm all alien radio equipment? In 100 light years of space, how much of the transmission would be dampened by gas, gravity, etc? As the 21st century portion of the wave arrived at the receiver, how long would it be before all the transmissions sounded like 0s and 1s (announcing Earth's digital era)? Would the alien need special equipment? Or would any old radio pick up something, whatever frequency it was tuned to?

If two planets coincidentally started broadcasting around the same time, would the alien pick up a mixture of the two planets' frequencies? Or would the waves somehow cancel each other out as they meet on their individual journeys through space-time?

What aliens could learn from the stuff we’ve left in space

Even in space, where none of us live, some of what we’ve left is space junk: stuff orbiting the earth that nobody particularly intended to leave anywhere. But much of what we’ve left in space is intentional. Some of it is symbolic artifacts intended for an audience of people here on Earth - the fallen astronaut, the American flag on the moon, a CD containing a list of over half a million people who wanted to send their names to a comet, courtesy of a NASA probe. In some cases, however, we are also sending a deliberate signal out beyond Earth, to be received by forces unknown. Rather than just listening for radio signals, which has been a staple of the Search for Extraterrestrial Intelligence, some earthlings have become interested in actively reaching out - broadcasting radio messages to anyone, or anything, out there that might be able to hear them. For reasons that are perhaps obvious, these are controversial projects.

Alien space bats (ASBs) is a neologism for plot devices used in alternate history to create a point of divergence that would otherwise be implausible. [edit]Definition

"Alien space bats" originally was used as a sarcastic attack on poorly written alternate histories due to lack of plausibility. These attacks are usually phrased as the need for alien space bats or by saying the alternate history has gone into "ASB territory". This original definition was used by one critic to criticize Harry Harrison's Stars and Stripes trilogy.[1] The term eventually evolved into a deus ex machina to create an impossible point of divergences.[2] Examples include changes to the physical laws of nature, introducing magic into the world, time travel, and advanced aliens interfering in human affairs. An example of aliens interfering in human affairs to change the direction of history is Harry Turtledove's Worldwar series.[3]

We've dedicated this Power Grid to the most disgusting alien civilizations to ever grace the page, screen, or hard drive.

Why is biology used as technology the easiest way to make aliens seem alien? Why are the bad guys’ ships always covered in strange fluids and dubious orifices?

And for another thing! Why are the ships in Star Trek and Galaxy Quest so damp?

In 1972 NASA sent into deep space an interstellar probe called Pioneer 10. It bore a golden plaque.

The art historian Ernst Gombrich offers an insightful commentary on this:

  The National Aeronautics and Space Administration has equipped a deep-space probe with a pictorial message 'on the off-chance that somewhere on the way it is intercepted by intelligent scientifically educated beings.' It is unlikely that their effort was meant to be taken quite seriously, but what if we try? These beings would first of all have to be equipped with 'receivers' among their sense organs that respond to the same band of electromagnetic waves as our eyes do. Even in that unlikely case they could not possibly get the message. Reading an image, like the reception of any other message, is dependent on prior knowledge of possibilities; we can only recognize what we know. Even the sight of the awkward naked figures in the illustration cannot be separated in our mind from our knowledge. We know that f

In the summer of 1899, whilst alone in his Colorado Springs laboratory working with his magnifying transmitter, the inimitable Nikola Tesla observed a series of unusual rhythmic signals which he described as 'counting codes'. Having just detected cosmic radio signals for the first time, Tesla immediately believed them to be attempted communications from an intelligent life-form on either Venus or Mars, and later said of the experience, 'The feeling is constantly growing on me that I had been the first to hear the greeting of one planet to another'.

The next year, Tesla was asked by the Red Cross to predict man's greatest possible achievement over the next century. The letter below was his reply.

A much-needed transcript follows.

The planned October 9, 2009 bombing of the moon by a NASA orbiter that will bomb the moon with a 2-ton kinetic weapon to create a 5 mile wide deep crater as an alleged water-seeking and lunar colonization experiment, is contrary to space law prohibiting environmental modification of celestial bodies. The NASA moon bombing, a component of the LCROSS mission, may also trigger conflict with known extraterrestrial civilizations on the moon as reported on the moon in witnessed statements by U.S. astronauts Buzz Aldrin and Neil Armstrong, and in witnessed statements to NSA (National Security Agency) photos and documents regarding an extraterrestrial base on the dark side of the moon.

If the true intent of the LCROSS mission moon bombing is a hostile act by NASA against known extraterrestrial civilizations and settlements on the moon, then NASA and by extension the U.S. government are guilty of aggressive war which is the most serious of war crimes under the U.N. Charter and the Geneva Co