Is the Truth Really Out There?
At a 2015 press conference, NASA’s Ellen Stofan and John Grunsfeld predicted that astrobiologists would finally detect alien life within the next 20 years. Once, this would have been viewed as a rash statement, but today, weighty evidence suggests that warm, wet environments habitable by forms of life we would recognise exist throughout the Universe. Our understanding of life’s fingerprint and evolutionary manoeuvres grows by the day. The potential existence of sentient aliens and extraterrestrial cultures, on the other hand, remains controversial. It is the loneliest question in the cosmos – are we the only life forms in the Universe? The enormous size of our Galaxy, containing potentially 400 billion stars, makes it difficult to imagine that our planet is isolated in its status as the host of intelligent life. Somewhere out there, surely, are other life forms with whom we might be able to communicate – at least at some level. If they are out there, why have they not contacted us and are we even capable of detecting their presence? One assumption is clear – that any civilisation, by the mere fact that it has become a developed society, is intelligent. So what exactly is the fingerprint of intelligence? Who decides what intellect actually is? And do we as a species have enough of it to be able to find and recognise it elsewhere?
The Search for Answers
Our interest in whether or not life is out there stems from our ability to see the stars, and recognise that we are but one lowly planet orbiting just one of them. The notion that vast galactic empires may be conducting their own business in outer space remains conjecture that is based on apparently logical conclusions drawn from our own origins. We know that microbial life evolved on the Earth at least, and that life then took many twists and turns via natural selection and some chance events to develop complex multicellular bodies and brains, societies and finally technologies that could provide a means of transport to other planets – maybe one day to other stars. Who is to say this might not equally occur on any of the billions of other habitable planets we believe twirl out in the cosmos? The search for sentient life is not just scientific but also spiritual, based on a belief it is out there somewhere.
We want to answer one of the world’s oldest questions: ‘Are we alone in the Universe?’ There was intensive debate about this issue even in antiquity. The atomists, who, as their name suggests, perceived correctly that atoms were the basic material of which everything is made up, believed in a plurality or a number of worlds. Yet, the Aristotelians held the opinion that we live in a closed cosmos with Earth at its centre. In the medieval age, philosophy and theology were dominated by the Aristotelian world view, until finally the Copernican revolution paved the way for the belief, and later proof, that there are many solar systems similar to ours in the vastness of space. Two widely assumed principles supported the idea that life is abundant in the Universe: the principles of plenitude and mediocrity. The former holds that a Universe made by a perfect Creator should be as rich as possible – and what universe could be richer than one that gives birth to and provides a home for a plenitude of life? The latter suggests that every place in the Universe that has similar molecules and shares similar laws of physics to Earth, would be likely to develop along a more or less similar route as our planet. The resulting multiplicity of Earth-like planets is a principle held by many in modern science. Nevertheless, whether or not that principle also applies to the existence of life remains an open question.
The Oddity of ET
In an attempt to quantify the possible number of cultures present in our Galaxy, the astronomer Frank Drake formulated a completely unsolvable equation in 1961 that, despite its unknowable and currently improvable answer, has gone down in history and is taught on all planetary science courses. The equation below is not some mind-boggling mathematical calculation – just a useful, relatively simple tool to help us contemplate the variables we must incorporate when considering the question of life elsewhere, and it is actually quite intriguing. Here it is:
N = R* × fp × ne × fl × fi × fc × L
We are trying to figure out the value of N, which represents the number of civilisations in our Galaxy with whom radio communication might be possible. To arrive at this number, a variety of factors must be taken into account. Starting at the beginning, R* is the average rate of star formation in our Galaxy. Estimates for the number of stars in the Milky Way vary from a low of 100 billion to a high of 400 billion. Estimates for the age of the Milky Way also vary from an infant of 800 million years to a grandfather of 13 billion years. If we go with the lowest star count and the oldest age for the Galaxy, the average rate of star formation works out at 7.7 new stars per year. If we go with the highest star count and the youngest age for the Galaxy, the average rate of star formation becomes 500 new stars per year. The rate of star formation in the galaxy is not constant over time, however; stars were formed at a much faster rate in the Galaxy’s earliest moments, and not all stars are created equal or deemed useful for hosting life. Today, estimates for the overall rate of star formation range from 5 to 20 new stars per year and the rate of formation of Sun-sized stars, around which intelligent life may arise, is in the order of one per year.
The next term, fp, is the fraction of those stars that have planets. At the time Drake wrote his equation, this was a complete unknown. Since then, nearly 2,000 exoplanets have been found orbiting a variety of stars. Estimating the total number of planets in the Universe is difficult, but it is possible that, in the Milky Way, each star has an average of 1.6 planets – yielding 160 billion alien planets in our home Galaxy alone. This number is making the chances for finding communicable life look a little better. The third term, ne, is the average number of planets that can potentially support life per star that has planets. In his original equation, Drake optimistically assigned a value of 2 to this parameter, meaning that he proposed on average two Earth-like planets per star for those stars with planets. The answer to this remains unknown, but out of the thousands of exoplanets discovered, small, rocky worlds similar to our own are popping up everywhere, and some of them may be capable of hosting life as we know it. The last four parameters, fl, fi, fc and L, are, as you may have guessed, also not known – perhaps forever unknowable – and are very hard to estimate. They are in order: the fraction of planets that actually go on to develop life at some point, the fraction of those that actually go on to develop intelligent life, and the fraction of those intelligent civilisations that develop technology that releases detectable signs of their existence into space; finally, L is the length of time for which civilisations exist.
The most contentious is fi, unsurprisingly. We have only one example, Earth, where life is abundant and humanity has reached a level of technology that allows it to scour the Universe for other life, and can broadcast its own existence into space. Is human-like, technological intelligence likely to be common across the Universe? Are we merely an evolutionary blip? Or is intelligence something that the entropy-driven, complexity-producing Universe will inevitably converge on? It may even be that Earth (and all intelligent life on it) is an early bloomer and that we are not hearing from advanced alien civilisations because the Universe has not had the time to spawn other habitable worlds on which they could flourish.
In case you are wondering, the estimated solutions to the Drake Equation range from 0 intelligent, communicating civilisations in the Galaxy, to 10,000 – not especially illuminating. We may be one of a myriad of intelligent species or we may be alone. Even if one day we were to receive signals from another intelligent species, the problem would remain of how to reply and stay in contact over such measureless distances, even ignoring the obvious barriers of communication media and language. It could well be that extraterrestrial life exists in parts of the vastness of the Universe that are beyond the possibility of contact or even of mere observation. Yet finding life outside the Earth – even non-intelligent microbial life – would be an important step towards a better understanding of the Drake Equation, and take us further along the yellow brick road to communication.
Conversations with my Cat
As far as we know, no cat can compose an email, no whale can sing to us in our own language and no bird can solve mathematical equations. Only humans can perform such intellectual feats, presumably, some may say, because we are smarter than all other animal species – at least by our own definition of intelligence. Just as with life itself, there is no globally accepted definition of intelligence. It has been described in many ways, from a capacity for logic, to abstract thought, understanding, self-awareness, communication, learning, emotional knowledge, memory, planning, creativity and problem-solving. At its most simple, however, intelligence is the ability to identify and receive information and retain it as knowledge for later use: now the scope for recognising other intelligent species on Earth widens.
Life based on one basic blueprint has existed on Earth for 3.7 billion years – more than a quarter of the age of the Universe – and it took 1.8 billion of those years for the first multicellular versions to appear. Life on Earth is divided into bacteria and fungi, plants, and animals, but nervous systems and brains only developed in animals. Of these animals, some 60–80 lines developed, but only in the chordate vertebrates did intelligence appear. Within the vertebrates, such as fish, amphibians, reptiles, birds and mammals, higher intelligence only developed in mammals. The hominids first appeared some 3–6 million years ago, but Homo sapiens evolved only in the last 200,000 years, producing a number of different civilisations, with only the most recent developing technology capable of seeking out other intelligent life. This last development of space-voyaging folk took place only in the last 100 years of the immense 4.55-billion-year lifespan of the Earth. The evolution of hominid intelligence is attributed to specific environmental challenges and it is a misinterpretation of evolutionary theory to see this rise of intelligence in us as a necessary process. Should we accept that it was pure chance and a lucky mutation or two? It could have appeared in fish or dinosaurs, or may not have arisen at all, but intelligence is the only adaptation to have allowed a single species to establish complete domination over the rest of the natural world. Will humanity with all its knowledge survive 100,000 years from now? We as a species are good at reproducing to ensure the longevity of our race, but are yet to prove we can use our gift of intelligence to survive across the ages.
Cosmic Conundrums and Fermi’s Paradox
This hope of the existence of long-lived alien civilisations capable of first contact is what drove the Italian physicist Enrico Fermi to utter his famous phrase, ‘Where is everybody?’ In 1950, amid a spate of rumours of flying saucers crashing into New Mexico, Fermi reasoned that if only one in a million stars in the Milky Way had planets with intelligent beings and they began space travel, then within a few tens of million years they should have spread throughout all regions of our Galaxy, including our Solar System. So why, he wondered aloud, have we not seen them? Why have they not made their presence known? This became known as the Fermi Paradox. If Earth is not unique in having intelligent life, then civilisations should already have evolved many times over in the Galaxy, since there are billions of stars older than the Sun. If any of these civilisations wished to colonise the Galaxy, they could have done so by now. There are two answers to his question: (1) we are alone, or (2) we are not alone, and the first solves the paradox. Fermi was obviously posing the question because of his belief that we are not the only intelligent life forms floating in the sea of space. A number of solutions has been proposed, none of them provable yet, of course, but an answer I particularly like is that we are akin to animals in a zoo. Humans are bound by our current level of technological intelligence to travel only within our own Solar System. Any civilisation able to overcome these limitations would need to be vastly more advanced – so advanced, in fact, that they may see striking up a conversation with us with our current science, technology and social abilities, as futile, as we would view trying to chat to an ant colony scurrying around an anthill. Hence, we have heard no news. Perhaps more advanced civilisations are waiting until we are worthy. Or, if they don’t exterminate us for being so inferior, they may assign us (or already have assigned us) to conservation and study in a galactic zoo with the aliens as our keepers. Perhaps they are reading this and laughing at us for not already realising.
Barriers to Life
The Great Filter is a probability barrier, a concept that some mechanism we cannot yet understand may have prevented life, or will prevent life in the future, from expanding into the Universe. We think there may be one or more highly unlikely evolutionary stages whose occurrence is paramount for an Earth-like planet to form and to produce an intelligent civilisation of a type that would be visible to us with our current observation technology. If you begin with trillions of potential germination points for life, and end with a total of zero extraterrestrial civilisations that are observable – something is happening somewhere along the line to affect (arrest or slow down) evolutionary development. The critical evolutionary step(s) towards intelligent life must be essential enough, yet unlikely enough, that even with many billion rolls of the dice one ends up with nothing: no aliens, no spacecraft, no signals. This very powerful Great Filter can change the course of history. So what could this Great Filter be? And importantly when did it happen? There are three possibilities: it already transpired in the distant geological past; it has not yet taken place; or … it is happening right now.
If the filter were in the past, this would explain why we have not yet come across aliens, because if the rise of intelligent life on any one planet is sufficiently improbable, then it follows that we are most likely to be the only such civilisation in our Galaxy or even in the entire known Universe. A potentially unique and extremely improbable step occurred at some point in our history that allowed for intelligent technological life to arise on the Earth. If the Earth movie were stopped and played again from the start, the rise of sophisticated intelligence might not happen in its re-run. Evolutionary biology, at least for the moment, does not enable us to calculate the probability of the evolution of intelligent life on Earth, but we know that some events were critical to its success and may therefore be good candidates for a Great Filter that led down the path to intelligence. One criterion is that the Great Filter must only have happened once (as there is only one example of intelligent life), since features that have evolved multiple times on Earth are demonstrably likely to occur on other worlds. The evolution of flight, sight and limbs, which have all occurred on Earth several times, are ruled out as possible candidate events. Another possible Great Filter is that an event took a very long time to come to pass even after the perfect conditions for it to occur were present. The emergence of life in the first place is an example. As far as we know, the transformation from building blocks into a reproducing, metabolising organism may have occurred only once and have taken hundreds of millions of years to get going, even after the planet had cooled sufficiently to enable a wide range of organic molecules to be stable. It actually took 1.8 billion years for prokaryotes to evolve into eukaryotes, which is quite a long time. This transition is a good candidate for being the Great Filter.
A worrying possibility is that the Great Filter lies in our future. This would mean that some cataclysmic unknown event prevents almost all technological civilisations at our current stage of development from progressing to the point at which they engage in colonisation of space and make their presence known to other technological civilisations. For example, it could be that any sufficiently technologically advanced culture always discovers or creates very powerful weapons and causes its own annihilation. We will never know whether this is the case or not until it happens to us, or until we chance upon another civilisation at this point in its own evolution. A final thought to ponder is whether the Great Filter is happening right now! The greatest obstacle to exploration of the cosmos is the distances involved and the ability of humans to undertake and survive the journey. Could distance and physical frailty in fact prove a Great Filter, and indeed prevent other species from contacting us?
The Search Begins …
The vast immeasurable expanse of the Universe and the enormous impact that first contact would have on our world has led a few brave souls to take on the scientific challenge of searching the cosmos for intelligent beings. What drives them is the belief that humanity is a normal outcome of physics, chemistry and biology. Since the 1950s, a small number of astronomers across the world have risked ridicule by joining in a search for other sentient beings. In 1984, they founded the SETI Institute (the Search for ExtraTerrestrial Intelligence), based in California. Utilising massive arrays on Earth, as well as space telescopes, SETI scans the heavens for any indication of radio or other communications beamed in our direction. At the time of writing, no verifiable signal has yet been received. The Universe may be teeming with life, but it is currently preserving its secrets.
Project Ozma
Between April and July 1960, Frank Drake, who wrote the quirky unsolvable equation presented earlier, undertook humanity’s first effort to identify radio transmissions from alien sources. Based at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia, Project Ozma was born, named after the queen of L. Frank Baum’s fictional land of Oz, described as ‘very far away, difficult to reach, and populated by strange and exotic beings’. Drake initially directed his search towards two stars, similar in age to our Sun, known as Tau Ceti and Epsilon Eridani, located some 11 light years (66 trillion miles) away. For six hours every day, Project Ozma’s radio telescope scanned frequencies emanating from regions of cold hydrogen gas, looking for repeat sequences of pulses or series of prime numbers such as 1, 2, 3, 5 or 7, that might indicate some form of artificial intelligent message. A thrilling red herring early in the programme proved to come from a now not-so-secret military experiment; besides that, there came only static. Nonetheless, the pioneering Project Ozma generated enormous public interest, and made the search for the technological fingerprints of civilisations on other worlds scientifically feasible.
Prime Numbers and Laser Pulses
In the story Contact, published in 1985 by Carl Sagan, a young SETI researcher finds strong evidence of ET life within a radio transmission and is chosen to represent humanity to make first contact. The signal is a repeating sequence of prime numbers apparently sent from the star Vega, and contains 60,000 pages of data outlining plans to build a machine to allow one human occupant to communicate with the alien life forms. This story, written by an astrobiologist and SETI researcher himself, was based on real techniques, real theories and even real scientists. Jill Tarter (who gave a fantastic TED talk on this topic) acted as Sagan’s muse for the novel and was portrayed in the film adaptation by Jodie Foster. The book draws on the idea that alien signals could take many forms – from radio and light signals to laser pulses and even genetic manipulation. We can still only guess at the means by which a more advanced civilisation might choose to make contact.
So far the hunt for alien signals has mostly used radio waves, based on the theory that radio is a relatively easy and cheap way to send signals long distances through space. The SETI Institute uses powerful radio telescopes on Earth to search for signals focused at a single spot on the radio dial, called narrow-band signals, and those that repeat in a mathematical pattern. Huge numbers of natural bodies make radio noise, such as small pulsars (pulsar actually being short for ‘pulsating radio star’), although not in regular arrangements; yet the only thing that makes a narrow-band signal, as far as scientists know, is an artificial transmitter.
The SETI Institute’s Allen Telescope Array (ATA) is solely dedicated to the search for signals broadcast by intelligent alien life. Located at the Hat Creek Observatory in the Cascade Mountains of California, the ATA is an ambitious array of multiple small dishes whose power can be combined to form the equivalent of a single large-dish antenna, but positioned in several different directions to make a more powerful radio ear than ever before. Because of its ability to study many areas of the sky at once, every day of the week, it has the ability to listen to a truly significant sample of the cosmos.
Exquisitely sensitive, the ATA could detect emissions from powerful radars equivalent to those we have on Earth at a distance of dozens of light years. Any society even slightly more advanced than our own could manage a deliberate radio transmission that the Array could tune into. For SETI researchers, it is only a matter of aiming the antennae in the right direction and establishing the correct frequency. Among its targets are the exoplanet candidates discovered by NASA’s Kepler space telescope. For the first time in the history of the search for sentient life, telescopes can be pointed at stars known to host planetary systems, including those that may feature planets similar to Earth – just the type of worlds that might be home to a civilisation capable of building radio transmitters and receivers.
We assume that other intelligent civilisations would broadcast radio signals just as we do, but although radio-loud ourselves over such a short phase, we are already reducing our interference through switching to fibre-optic cables and telecommunication satellites. Furthermore, we are assuming that other intelligent civilisations would even want to talk to us, or know to look in our direction. What if other planets were host to hyper-intelligent space dolphins, who never rise above the sheltering waters of their world, in an attempt to evade dangerous stellar radiation? They would not even know there were other stars, let alone other intelligent beings wanting to communicate with them, nor would they probably care.
If listening for the one unexplainable radio message is a bit of a long shot, how else could we go about it? Laser pulses are a favourite choice. Russian and American scientists have scanned the skies periodically over the last couple of decades hunting for laser light, which is not only distinguishable from other natural types of light such as starlight, but as far as we know can only be produced by an intelligent source. Ghostly subatomic particles called neutrinos are perhaps better suited for transporting a message over long stellar distances than radio or optical signals, so it may be wise to look out for neutrino-based alien Morse code as well. We could also look for evidence of asteroid mining – humans are already seeing the potential benefits to our own civilisation of obtaining mineral resources from our local rocky belt, so why would an alien civilisation not do the same? Perhaps evidence could be found through unusual changes in the chemical composition of the asteroid belt, irregular-shaped chunks missing from images, an increase in the size and amount of debris surrounding a celestial body, or other changes detectable from Earth. An unfortunate side effect of our own culture is pollution, but this means we could search for similar dirty signatures in alien atmospheres. If there are non-natural chemicals, such as chlorofluorocarbons, in a planet’s atmosphere, this would also be a sign that there might be someone with technology on the ground.
Taking this a step further, we could actually look for evidence that may have been sitting right here on earth for billions of years – who is to say that aliens have not been here at some point already and left behind some artefact or message for us to find? Our DNA encodes information – could it have an alien message written into it? It is of course highly unlikely, but still in the outer realms of possibility. We could even take a cue from science fiction and look for the signature from an alien spacecraft zooming by. We may just get lucky one day and receive an email. A group of scientists have set up a website inviting ET to get in touch, and although 99.9 per cent are hoaxes, only one needs to be real.
The Power of Civilisation
Believe it or not, should we ever make contact with ET there actually exists a ruler by which alien civilisations can be measured. It is called The Kardashev Scale. Currently classed on this scale by Carl Sagan as a Type 0.7 civilisation, the question being put is whether humanity will ever advance past the Moon and finally make our way into the ranks of the Type Is? As a civilisation grows and advances, its energy demands will increase rapidly as a result of population growth and the power requirements for the technology this greater number of people will supposedly build and operate. The Kardashev Scale was created to measure a theoretical civilisation’s mechanical progression against how much energy it has available. The scale was originally designed in 1963 by the Russian astrophysicist Nikolai Kardashev, who created three base classes, each with an energy disposal level: Type I (1016W) Type II (1026W), and Type III (1036W). Recent astronomers have extended the scale to Type IV (1046W) and Type V (all the energy available in all universes and in all realities). The human race still has a long way to go before being awarded Type I status as we continue to sustain our energy needs from fossilised plants and animals, and is therefore at the bottom of the civilisational heap.
A Type I designation is bestowed upon populations who have been able to harness all the energy available from their host planet and the energy that reaches it from their own star. The population will then have the knowledge and know-how to collect and stockpile this energy to match the demands of its growing numbers. However, humans being able to harness all Earth’s energy is hard to fathom – it would mean we could control all the natural forces on the Earth, such as volcanoes, the weather and even earthquakes.
A Type II civilisation can harness the power of its local star directly, controlling the star itself. One hypothetical method of doing this is called a Dyson Sphere, named after the physicist Freeman Dyson, who had the idea that a growing technological culture would ultimately be limited by access to energy, and that advanced power-hungry civilisations would be driven to harvest all available light from stars. Such a device would consist of vast clusters of machines that would encircle a star, harvesting most or all of its energy output and transferring it to the civilisation’s own planet for later use. Another idea for capturing stellar power involves the control of nuclear fusion, the mechanism that runs stars, and the harnessing of this power in an incredibly large reactor. Perhaps nearby gas giants could also be utilised for their hydrogen, slowly drained of their chemical life source by an orbiting nuclear reactor. What is attractive about this level of advancement is that should a moon-sized object enter the Solar System on a collision course with our little planet we would have the ability to vaporise it. Perhaps we could even play a planetary game of chess – moving our planet out of the way or sacrificing another planet of our choice to block the invader’s path – cosmic checkmate.
Searching for evidence of this theory, at the end of 2015, scientists monitoring NASA’s Kepler space telescope observed a bizarre star snappily entitled KIC 8462852 that was shown to be emitting a strange light pattern. As detailed in Chapter 8, Kepler searches for dips in starlight created when a planet transits in front of its host star. KIC 8462852 stood out as being strange because the star was witnessed dimming by 20 per cent, unlike the normal one per cent created by the passing of a planet. It was also seen to be surrounded by a mass of matter consistent with debris found around a young star soon after its formation; this star, however, is not young and the debris appeared to be recent. Could this debris in fact be a megastructure similar to a Dyson Sphere? SETI astronomers have so far found no evidence of radio signals coming from this potentially alien astro-engineering project, but KIC 8462852 will now undoubtedly be the subject of SETI observations for years to come.
Once a civilisation has graduated from gaining control over a planet and then a star, making its own extinction almost impossible, what could possibly be next? Well, a Type III civilisation, of course: a galactic space-roving population with total control of energy, resulting in a master race with dominion over the Universe. These beings may even have evolved into self-replicating cyborgs or cybernetic organisms, both biological and robotic. In this scenario, the descendants of regular humans would be seen as a weak, inferior and primitive clan. The dominant humanoid species would have a population boom as they colonised the Galaxy, building numerous Dyson Spheres to leach the energy from each new star they came across, creating a huge network of stellar energy funnelling power back to the home planet.
Not alone in his beliefs, Kardashev considered a Type IV civilisation too advanced to contemplate. Could anything be more theoretically advanced and fictional than Dr Who-esque cyborgs harnessing the power of hundreds of stars? Nonetheless, some believe that even greater advancement is possible for a society. Step forward the Type IV civilisations that would be capable of harnessing the energy content of almost the entire Universe and travelling across the accelerating expansion of space. A Type IV civilisation would need to tap into energy sources unknown to us using bizarre, or currently unknown, physics. There is a further level – a Type V civilisation, where beings would essentially be gods, with the knowledge and power to manipulate the Universe and beyond at their will.
Cosmic Sightseeing
The human brain is the most powerful entity in existence as we know it – a biological supercomputer. As such, it gives humans a massive advantage over automated machines such as telescopes, rovers and space probes. It has superior pattern-recognition capabilities and allows for ingenious problem-solving strategies. In space, the unexpected is the norm and no being is better than a human at responding quickly to the unanticipated. Despite the fact that we would be the best entities to send in search of other life forms, long-distance space exploration is highly problematic for the human body. If we ignore the obvious issue of a lack of advanced-enough technology and propulsion systems even to blast humans off to far-flung star systems, our weak little bodies would not survive the trip. A short lifespan of up to 120 years is not compatible with the up to 80,000 years it would require with current technology to reach even the closest star, not to mention what spending that length of time in microgravity and exposed to the radiation of space would wreak physically on the human body and mind. It represents a perfect storm of immeasurable distance, slow travel speed, human frailty, short lifespans, and extreme cost, which in combination necessitate our reliance on technology to reach out to the stars and make the introductions for us.
This is not a bad second choice. Automated robotic probes have been sent to planets, moons, comets and asteroids, and to the very edges of our Solar System, and for the most part have been successful beyond our wildest imaginations. However, what about going beyond the Solar System to search for other life forms? That is a goal far beyond our current capabilities. In 1978, the probes Pioneer 10 and 11, were launched and after successfully completing their missions around Jupiter and Saturn, continued along paths that would eventually take them out of the Solar System. Today, they are heading towards the star Aldebaran, 68 light years from the Sun (which will take in the region of 2 million years). After 30 years of flight, they are still somewhere well within the Solar System and sadly all radio communications have been lost. Even though we will never know what, or even who, these probes meet on their journey, Pioneer 10 does bear a plaque inscribed with information about Earth and humanity – just in case it bumps into some beings from the Aldebaran civilisation. But if they reply to our message, will there still be anyone left on Earth to receive it?
Since voyaging into the cosmos looking for friends is challenging, and two-way communication is not possible with our current technology and short lives, we are focusing instead on sending messages in bottles, as well as listening out for them calling to us. Alien civilisations may even be able to eavesdrop on humanity by tapping into our TV and radio broadcasts. Considering that one of the first TV transmissions was of Hitler opening the 1936 Olympic Games – and we all know what happened soon afterwards – a worry is that this will not exactly inspire them to get in contact. In 1951, the first episode of I Love Lucy was broadcast and some 0.0002 seconds later, the signal headed into space. Maybe this, or re-runs of Friends or David Attenborough documentaries could make humanity and the Earth seem more appealing. Given that stars in our galactic neighbourhood are separated by about 4 light years, in the past 50 years roughly 10,000 star systems may have been exposed to our TV shows. They must be rather confused about what on <insert alien planet name here> is going on over on that little pale blue dot – or perhaps they are as hooked on Game of Thrones as we are.
Hello?
We are not only broadcasting BBC Radio 2 and reality TV shows, but have actually sent complete messages into space. SETI most famously transmitted a communication to the stars in 1974 using radio waves from the Arecibo telescope in Puerto Rico, aimed at a globular cluster, M13, more than 25,000 light years away. Frank Drake and Carl Sagan composed the message, which included the numbers 1 to 10, atomic numbers of the elements of life such as hydrogen, carbon and oxygen, information on our DNA, a figure of a human (non-gender specific) and a graphic of our Solar System highlighting the Earth as the origin of the message. Sadly, the stars this message was aimed at will no longer be in the same spot by the time it arrives, but who knows who might pick it up along the way.
Three years later in 1977, the Golden Records were launched on both Voyagers 1 and 2, intended to communicate a story of our world to extraterrestrials, interestingly only portraying the positive sides of Earth – no warfare, hunger or disease – which makes sense. Who wants to make first contact with an alien civilisation only to highlight the less attractive aspects of life back home? In August 2012, Voyager 1 took its first steps towards becoming that beacon as it entered interstellar space, leaving our Solar System behind. The spacecraft is trekking towards a star called Gliese 445, and has a date with it in 40,000 years’ time. Of course, by this date it won’t be able to transmit home any data – in fact, by 2025 all of its scientific equipment will have stopped working (the equipment on board is already more than 40 years old, created before the CD and colour television). The Voyager message, however, is embedded in a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. Again, Carl Sagan led the charge and with his associates assembled 115 images and a variety of natural sounds such as surf, wind and thunder, birds, whales and other animals. To this they added musical selections from different cultures and eras, and spoken greetings from Earthlings in 55 languages, together with printed messages from the then President Jimmy Carter and UN Secretary General Kurt Waldheim. The launching of this record says a great deal about the hope and positivity of humanity. Since then, all missions to other planets and those designed to orbit and explore the Solar System have contained messages including information about the Earth and humanity, just in case any being comes across them.
After New Horizons flew by Pluto in 2015, it began a new journey towards the Kuiper Belt, following which it may one day become the fifth spacecraft to leave the Solar System and may even be the first to be discovered by an alien species some millions of years from now. Unlike Pioneers 10 and 11 and Voyagers 1 and 2, New Horizons was launched in 2006 without a welcome message, but following completion of its active mission there will be some space available on its computer for a message to be uploaded digitally. Unlike previous messages, however, this one, fondly known as the One Earth Message, will be a unique crowd-sourced message in a bottle, sent by people from all over the world. Who speaks for Earth? The answer is everyone. This literal selfie of our planet will aim to communicate to ET the real essence of the Earth, humanity and the other life forms that share our planet. If we did not believe there was even the slightest chance of intelligent life out there, why would we bother?
Much of today’s scientific exploration and data analysis looks to the public for help and support, such as the Zooniverse, which calls upon citizen scientists to help comb through mountains of data to aid scientists with classifying distant galaxies, spotting black holes, characterising surface features on Mars and even hunting for exoplanets. The quest for ET is no different. The SETI@home project has involved the worldwide public in a search for radio-wave evidence of life outside Earth for 16 years. Based at the Space Science Laboratory at the University of California (Berkeley), this project records and analyses data from the Arecibo Observatory by searching for narrow-band signals of possible extraterrestrial origin. As yet, no such signals have been found. Today, SETI@home continues its search for evidence of extraterrestrial life with hundreds of thousands of volunteers each hoping to be the one to find it.
What Happens if We Find it? What Happens if We Don’t?
As Carl Sagan wrote in Contact, ‘The universe is a pretty big place. It’s bigger than anything anyone has ever dreamed of before. So if it’s just us ... seems like an awful waste of space.’
NASA’s Kepler space telescope has helped scientists discover thousands of exoplanets, and has a very large field of view of 105 square degrees – comparable to the area of your hand stretched at arm’s length. Most astronomical telescopes have fields of view of less than 1 square degree so, although Kepler can monitor more than 100,000 stars, it is still a miniscule area of the Galaxy, let alone the Universe. Set to launch in 2018, NASA’s next-generation James Webb Space Telescope, together with its larger successors, will give scientists the opportunity to look for signatures of life in the atmospheres of exoplanets – although they will not be capable of distinguishing whether life forms are brainy beings or single-celled microbes. Astronomers now know that every star in the Milky Way galaxy has at least one planet orbiting it, so humanity’s first contact with alien life may one day be possible. It is also not just a case of where to look, but also when. The Arizona State University astronomer and author Paul Davies points out that even if a fairly close civilisation, say one 1,000 light years away, were to look through a telescope and find Earth, it would see the planet 1,000 years in our past. Why would they bother to send a message to a planet that had not yet discovered electricity, let alone built a receiver to intercept their message?
Even the discovery of some simple sort of ET life would be extraordinary. Finding non-sentient extraterrestrial life would help piece together our own origins and the history of life on Earth, and would be a momentous watershed event for the entire globe. If the discovery were of life that could say hello back to us – life as we know it would change forever.
UFO-spotters, Raëlian cultists and self-certified alien abductees notwithstanding, humans have to date seen no sign of any extraterrestrial intelligent civilisation. We have not received any visitors from space, nor have our radio telescopes detected any unusual transmissions from other worlds. But although no one has yet found life elsewhere, there’s no reason necessarily to despair. Mass extinctions have wiped out vast majorities of species in our planet’s nearly 5-billion-year history, and yet here we are. We can only assume and hope that any life existing elsewhere would be just as resilient.
But what if this really is all there is – and our isolation extends far into the Universe, or, and perhaps more likely, we do not recognise different life forms because some of our presumptions concerning how an alien civilisation might look and behave, based on our own experience, are incorrect? In 2015, the close examination of 100,000 galaxies near to our own concluded that none presented any irrefutable evidence of civilisations with highly advanced technology. Instead of listening for voices from the skies, scientists looked instead for heat signatures that would be produced by advanced civilisations, just as Freeman Dyson and later the Kardashev Scale predicted might exist. The idea is that, once a star is encased in a Dyson Sphere, its glow would be suppressed, but the engineered construction itself could be detected by the wasted heat oozing out from it. The same process is happening when your iPhone warms up during prolonged ‘Googling’. In some sense it doesn’t matter by what means a galactic civilisation generates or uses its power, because the second law of thermodynamics makes energy use hard to hide. They could construct Dyson spheres, draw power from rotating black holes or build giant computer networks in the cold outskirts of galaxies. Any of these would produce waste heat, but the search for objects emitting more heat than light in over 100,000 nearby galaxies has yielded, perhaps unsurprisingly, no positive results. No Type III civilisations have been found – yet.
Over the years, to explain away the endless silence of deep space, researchers have created a vast assemblage of possible explanations for the disappointing lack of any intelligent alien life. Perhaps we are indeed alone. Perhaps the laws of astrophysics and biology make intelligent life vanishingly rare, and the rise of humans was serendipitous. Perhaps technological civilisations always destroy themselves once they reach a certain point. Perhaps interstellar travel is simply too hard, too slow or too boring for any advanced civilisation to bother undertaking. It could be that galaxy-sterilising explosions such as gamma-ray bursts in the cosmic past suppressed the rise of advanced civilisations and now that these have quietened down, we humans had the chance to arise and are the foundations for civilisations yet to come. Perhaps, and I like this idea best, any advanced civilisation will have become in tune with its natural environment, value nature’s role in its survival and will be working in harmony with it. In this scenario, our supremely intelligent and compassionate aliens would not produce waste heat, light, nor electromagnetic signals from a repository of profligate technologies – so it will be less easy to find them until we use our intelligence to do the same.