Is Anybody Out there?
The universe is vast and ancient, containing billions of stars. The likelihood is that other Earth-like planets, suitable for intelligent life, exist out there. Given the vast amount of time available, some of these suitable planets should have evolved intelligent life, some of these lifeforms should have developed interstellar travel, which should in turn have enabled them to colonise the galaxy within just a few tens of millions of years. So, we should expect the universe to be teeming with intelligent life. Any yet, we find none. Despite 50 years of searching, we have not yet found any evidence of extraterrestrial civilisations. We have failed to detect artificial signals in space, and we have failed to find any artefacts of intelligent life. This is the basic tenant of the Fermi paradox; we expect intelligent life to be prevalent in the galaxy, and yet we are unable to find it.
There are a number of reasons why we haven’t yet found extraterrestrial intelligence (ETI). Firstly, it may simply not exist. And there a number of good reasons to suspect this – the evolution of intelligence on Earth, where conditions are clearly suitable, has only occurred very recently. In fact, getting past single-celled simple lifeforms was extraordinarily difficult, and took around 3 billion years. It seems that when we look at the history of life on Earth, evolving life itself wasn’t that hard (it happened virtually as soon as conditions permitted), but evolving complex life was very difficult, and sentience has only been achieved very recently. In his 2006 book, Nick Lane suggested that the mitochondrial symbiosis which led to the evolution of eukaryotic cells may well represent an unrepeatable event limiting the evolution of complex life. However, given the enormity of space and the vastness of time, many scientists still believe extraterrestrial intelligence is likely.
ETI could well be expected to be very rare in the universe, and this may contribute to our difficulty in detecting them. Perhaps ETIs exist but are so distant from us that contact is impossible. Or, perhaps ETIs tend to be very short lived, particularly if intelligent civilisations have a tendency to destroy themselves. Assuming that rapid expansion is unsustainable and destructive, it is reasonable to expect that surviving intelligent civilisations are slow-expanding, which might explain why they haven’t reached us yet. In 1997, Carl Sagan and Frank Drake estimated that there may be as many as 1 million civilisations at or beyond our technological level within our galaxy alone. Assuming an even distribution, our nearest intelligent neighbour would be about 300 light years away. Another possibility is that ETIs are aware of us, but have chosen to remain invisible for some reason. Perhaps they have decided we are not worthy of communication, yet. One idea, known as the zoo hypothesis, suggests that ETIS are observing us from a distance. Perhaps when we pass some threshold of civilisation or technological ability they will choose to initiate contact. Alternatively, intelligent life might be out there, and may even be attempting to communicate with us, but we haven’t yet tuned into the right wave-length, or they may be using methods of communication we aren’t aware of.
Knowing Where to Look
Determining the correct way to communicate with ETI is a difficult task. Our communication methods on Earth all utilise electromagnet waves, and this is how we have proceeded for our initial attempts at galactic communication. However, the electromagnetic spectrum is huge, including radio, infrared, visible light, ultraviolet and x-rays, and it is nearly impossible to search all of these for messages. Electromagentic radiation is also a pretty poor method for galactic communication because it’s speed is limited by the speed of light. On Earth that works fine; the distances are small enough that it allows nearly instantaneous transmission of information. But in space, distances rapidly become prohibitive. Communication with a sentient society even just 50 light years away would happen on a timescale of 100 years, and so if we do eventually succeeding in communicating, it will be an intergenerational project. ETI might have developed a more advanced method of communication that avoids these problems, but we might not be capable of detecting it with current technology.
Assuming ETI is tuned in to electromagnetic radiation, they might already know about us. For the last 100 years we have been ‘leaking’ radio broadcasts into space, and television for the last 50 years. Thus, a civilisation 50 light years away could be watching our earliest TV shows, but it would take another 50 years for us to hear their reply, if they made one.
The Benefits and Costs of Communication and Contact
Although we haven’t yet found ETI, projects like SETI and METI continue the search, so it is important to consider what the possible outcome of successful contact might be. Merely finding definitive proof of extraterrestrial intelligence could be beneficial or harmful to humanity. The philosophical implications of proving that we are not alone in the universe are profound, but probably not universally good or bad. A greater understanding of our place in the universe and of sentience and intelligence itself could be of great intellectual benefit, and ETI would undoubtedly represent humanity’s greatest discovery. However, for those whose views depend on the belief that humanity is in some way special and privileged (e.g. followers of many religions), this information could be extremely damaging. Of course, if extraterrestrial intelligence exists, those world views are already erroneous, regardless of whether we are aware of its existence, however detection of ETI could be considered harmful to the wellbeing of those whose world views are challenged by it. The detection of ETI could serve to unify humanity, but it could exacerbate conflict between people with differing world views.
If our communication with ETI goes beyond mere detection, beyond a simple wave across the galaxy, then the outcome of such interaction would depend largely on the nature of the ETI in question. If the ETI is cooperative, then interaction could be hugely beneficial. Interacting with ETI might expand our scientific understanding of physics and chemistry. Furthermore, a more advanced society might provide insight or assistance in many of humanity’s problems, such as sustainability, poverty or disease. However, whether a distant civilisation would have any relevant advice is questionable. Of course, ETI might equally be uncooperative – an extraterrestrial civilisation might choose to attack us, eat us or enslave us. We might win in this scenario, however this seems unlikely under the assumption that ETI would likely be more advanced than us.
Most likely, should ETI be aggressive or uncooperative, this would not end well for humanity. There are several possible ways in which ETI might deliberately harm us (and also a few in which they unintentionally do so, which I shall return to shortly). ETI might be selfishly motivated and may choose to harm us for their own benefit. When we look at how humans have tended to respond to the discovery of previously unknown intelligent life (e.g. newly discovered societies, intelligent apes), the outlook is not good. A selfish, intelligent extraterrestrial-civilisation might chose to enslave us or capture us for study, attempt to convert us to their religious beliefs, capture us and use us for entertainment, or simply stuff us and keep us as a trophy. Or perhaps humanity would be viewed as a tasty snack.
Alternatively, ETI might chose to harm or destroy us in order to make the universe a better place. ETI might not be inherently aggressive, selfish or uncooperative, it could in fact be extremely ethical, but if it places value on different traits, it may pragmatically decide that humanity should be destroyed to the benefit of that trait. For example, perhaps the intelligent extraterrestrial civilisation places value on life, but decides that humanity, in our inefficient and unsustainable use of resources, is not the best way to maximise life on Earth. Alternatively, an ETI that places value on civic infrastructure may chose to destroy Earth in order to make space for an interstellar bypass (see Douglas Adams, 1979). Ultimately, should the ETI deem humanity as not the best use of the space available, they may chose to destroy us for the benefit of the rest of the universe.
Ultimately, the outcome of any interaction with ETI is likely to depend on the nature of the ETI. We cannot predict whether ETI would be hostile or helpful, but there is some reason to believe they might be helpful – aggressive and non-cooperative strategies tend to be risky, and so such societies might not survive very long. Sustainable and long-lived populations are likely to grow slowly and to have already developed solutions to manage their resources, so might be less likely to be hostile. However, even a generally cooperative ETI might be hostile towards humanity if we are perceived as threatening. We are unlikely to be seen as technologically threatening, but perhaps extraterrestrial life would view the trajectory of our civilisation to be threatening – we are currently developing rapidly and unsustainably, and if this were to continue on a galactic scale, we might be seen as a threat. Just as our unsustainable growth is a major threat to the other species with which we share Earth, continuing this growth into galactic civilisation might not end well for other extraterrestrial civilisations, and any ETI with which we may make contact might choose not to take that risk.
Whether ETI is friendly or not, they may unintentionally harm us if they bring disease, invasive species, cause accidental physical damage, or release dangerous technology (e.g. hostile artificial intelligence) or harmful substances (e.g. pollution) into the galaxy. This pattern is evident in our own interaction with other species on Earth – while we have negatively impacted on many species deliberately through hunting or eradication (e.g. pests), we have harmed many more species (and human civilisations) by accidentally introducing unfamiliar diseases, predators and competitors. We also frequently cause accidental harm to other species by destroying or polluting their habitat as a byproduct of our civilisation. If a visiting ETI carried a disease to which our defences were useless, the impact could be devastating. However, any disease would likely be adapted to infecting the ETI, so the potential for successful transmission and infection seems limited. It is relatively difficult to transmit diseases from one species to another (although as we are all aware, this is far from impossible), so the biological gap between humans and any ETI may well be too huge for any disease to jump.
The potential for contact with ETI to be harmful has led to calls to mitigate these risks. The most obvious solution is to stop looking, although that doesn’t prevent an ETI from looking for us. Alternatively, limiting contact to communication by preventing the ETI from entering our biosphere might prevent many potential problems. Again, this assumes we have power to prevent this, and a hostile civilisation more advanced than our own might not give us that choice. We ought to also carefully consider the nature of any communication we enter into. What information we chose to give out, and what information we are able to glean will strongly influence the outcome of any interaction. For example, gaining knowledge about an ETI’s biology might enable us to develop a cure to extraterrestrial diseases, but giving away information about our biology might leave us vulnerable to biological attack. Likewise, the information we reveal about ourselves might influence an ETIs judgement of whether we are valuable or dangerous to them. We must therefore be very careful about what messages we send out in our search for extraterrestrial intelligence. As an inherently curious species, it seems unrealistic to think that we will stop looking any time soon.
Want to Know More?
Baum et al (2011)Would Contact with Extraterrestrial Benefit or Harm Humanity? A Scenario Analysis. Acta Astronautica 68 (11 – 12): 2114 – 2129
Sagan and Drake (1997) The Search for Extraterrestrial Intelligence. Scientific American