OPINION | Cosmos Online | 14 January 2010
Some scientists are convinced life is common in the universe, but intelligence rare, says Wilson da Silva. As for how long civilisations last – and stay detectable – few are willing to hazard a guess.
TWO YOUNG PHYSICISTS at Cornell University in upstate New York, Philip Morrison and Giuseppe Cocconi, had long been interested in gamma rays. One spring day in 1959, Cocconi posed an intriguing question: wouldn’t gamma rays be perfect for communication between the stars?
The discussion that followed led to a two-page article in the British journal Nature entitled “Searching for interstellar communications”. Sandwiched between a paper on the electronic prediction of swarming in bees and one on metabolic changes induced in red blood cells by X-rays, the duo argued that if advanced extraterrestrial civilisations existed, and wanted to communicate, they would likely use radio.
They proposed a search of nearby Sun-like stars for signals at or near the 21-centimetre wavelength of neutral hydrogen, a band of frequencies between 1,420 MHz and 1,640 MHz. It’s a quiet region between two notable frequencies – the hydrogen line and the strongest hydroxyl spectral line, which combined yield water, considered essential for life. Hydrogen is also the most common element in the universe. Thus, was born, 50 years ago, the search for extraterrestrial intelligence, or SETI.
As Teng Mu wrote 3,000 years ago: “How unreasonable it would be to suppose that, besides the earth and the sky we can see, there are no other skies and no other earths?”
Throughout history, people have speculated about other worlds and life elsewhere. Italian astronomer Giordano Bruno was burnt at the stake in 1600 not only for suggesting Earth orbited the Sun, but that there were other inhabited worlds in the universe. German philosopher Immanuel Kant was convinced of this, as was the French nobleman and mathematician the Marquis de Laplace.
As Teng Mu, a Chinese scholar wrote 3,000 years ago: “How unreasonable it would be to suppose that, besides the earth and the sky we can see, there are no other skies and no other earths?”
SETI is like a search for a needle in a colossal haystack. As Jill Tarter of the SETI Institute has said, it’s not only unimaginably large, but nine-dimensional: three of space, one of time, two of polarisation (or perhaps photon rotation/twist), plus frequency, modulation, and sensitivity (a combination of transmitter power and distance).
“And that’s only the haystack we can describe with what we know about physics and technology in the 21st century, and from our terrestrial and inescapably anthropocentric vantage point,” she says. So we shouldn’t be surprised that a signal has yet to be detected, despite years of sporadic searches.
Will one ever be? It’s hard to know, when there are so many unknowns and so many variables. Some scientists are convinced life is common in the universe, but intelligence rare; as for how long civilisations last (and stay detectable) no-one hazards a guess.
Most SETI efforts have centred on detection. In fact, 2010 is the 50th anniversary of Project Ozma, the first serious attempt to listen for evidence of extraterrestrial transmissions. Led by astronomer Frank Drake at the U.S. National Radio Astronomy Observatory at Green Bank, West Virginia, it trained a 26-metre radio telescope at the stars Tau Ceti and Epsilon Eridani near the 1.420 gigahertz frequency.
Both are nearby Sun-like stars that (at the time) seemed reasonably likely to have inhabited planets. About 150 hours of intermittent observation during a four-month period detected no sign of extraterrestrial communications.
During Australia’s National Science Week in August 2009, we at COSMOS did something different – we transmitted a signal instead. With the support of Australian Science Minister Kim Carr and thanks to the staff and facilities of NASA and the CSIRO, a signal was sent to the nearest Earth-like planet outside our Solar System, known as Gliese 581d.
In August 2009, we did something different: we transmitted a signal to the nearest Earth-like planet outside our Solar System, known as Gliese 581d.
It consisted of messages left by the public on a website we created, HELLO FROM EARTH, and it was a howling success, with almost 26,000 collected. Gliese 581d is 20.5 light-years away, so the cosmic greeting won’t arrive until January 2030.
You can go online to check the progress of the message: in late October 2009 it crossed where we would expect the heliopause to be – the point where the interstellar medium and the wind from our Sun balance out. The next milestone is the Oort Cloud, a spherical cloud of comets nearly a light-year from the Sun which we estimate will be crossed sometime in 2010.
Truth is, we don’t expect a reply: chances are slim that there’s a radio telescope there, and that it just happens to be pointed our way at exactly the right time. However, as an exercise in science communication, it was a hit: it generated phenomenal media coverage and caused many to stop and think about the big unknowns.
But should we have done it? Some argue that we shouldn’t reveal our whereabouts – who’s to say extraterrestrials are uniformly benign? Others say it’s too late and that Earth has been leaking radio transmissions since the 1930s. The jury is out on this.
However, HELLO FROM EARTH was not the first such transmission nor – I suspect – will it be the last. It seems that humanity is driven to cast what the late astronomer Carl Sagan once called “bottles into the cosmic ocean”: the first messages sent into space were the simple plaques on NASA’s Pioneer probes (10 and 11, launched in 1972 and 1973), and golden records on the Voyager probes (1 and 2, launched in 1977).
Other cosmic message bottles include the beaming of the Beatles song “Across the Universe”, sent by NASA in 2008 from Madrid towards the star Polaris, and the Cosmic Call project, which in 1999 beamed a three-hour long message to four Sun-like stars within 70 light-years.
The very first serious phone call to the stars was actually made by Drake himself, to commemorate the opening of the massive Arecibo observatory in Puerto Rico in November 1974. A three-minute binary message, including the atomic number of DNA bases and a sketch of our Solar System, and was sent toward the globular cluster Messier 13.
While some may object, it’s worth noting that there’s no official decree against t doing so. The International Academy of Astronautics has considered the issue of transmissions on a number of occasions, and not ruled against them. Another body, the International Astronomical Union – the recognised authority on global astronomical matters – has no policy on METI (or Messaging to Extraterrestrial Intelligences), or active SETI as some have dubbed it.
It gets people thinking: are we alone? How does life arise, is it common in the universe or rare? What is intelligence, and how did it arise? Would we even recognise a new form of life if we stumbled across it?
I have no objection to selective broadcasts to the stars. I think it would be awesome if once a year, during Australia’s National Science Week, we picked a new extrasolar planet (out of the 100 or more new ones discovered every year) and ran an event like HELLO FROM EARTH that engages the public in sending messages to potentially habitable worlds.
It gets people thinking about the big concepts in science: are we alone? How does life arise, is it common in the universe or rare? What is intelligence, and how did it arise? We would even recognise a new form of life elsewhere if we stumbled across it? In order to think through these concepts, you need to cogitate on questions across a range of disciplines, from physics, geology, chemistry to biology, evolution, technology and intelligence.
It’s inspiring stuff, and likely to fire the imagination of young and old alike. Because it stirs the eternal questions within us: who are we, why are we here, and are we all there is? To be the only conscious, sentient beings in a universe so vast and limitless seems to me incredibly unlikely.
But even if life is common in the cosmos, I suspect intelligence may be a more challenging step that is only occasionally taken ... and does not always last. Not because I think intelligent civilisations wipe themselves out in war or some other calamity, but through no fault of its own – the asteroid that ended the reign of the dinosaurs would likely have made humanity extinct: nothing weighing more than 25 kg survived.
So it’s extremely unlikely our directed transmissions will be detected: the odds are against a technologically advanced civilisation being at the other end of a star targeted for a broadcast, and has just the right equipment pointing in the direction of our humdrum star on the edge of the galaxy at exactly the time we send out an electronic postcard. I think the messages we transmit into space give us a more interesting insight into ourselves: our hopes, dreams and expectations.
It stirs the eternal questions within us: who are we, why are we here, and are we all there is? To be the only conscious, sentient beings in a universe so vast and limitless seems to me incredibly unlikely.
The focus of SETI research is, appropriately, to search for signs of technologically advanced civilisations beyond Earth. And a worthy endeavour it is, for it would change our mindset, and our history, if and when it occurs.
In this, the global astronomical community does have protocols. If, one day, an extraterrestrial message is received, a special group of leading scientists – known as the SETI Post-Detection Taskgroup, led by Paul Davies of Arizona State University in Phoenix – are the people who are officially tasked with considering it and – if they think it appropriate – replying.
What an awesome responsibility: not only will they be the first to know that we are not alone: they will need to decide if to reply. And what to say. Now that is food for thought.
Wilson da Silva is the editor-in-chief of COSMOS Magazine, and the creator HELLO FROM EARTH, which sent interstellar messages from Earth. This was originally published in Cosmos Online on 14 January 2010.