In 1950, during a casual conversation with colleagues about a spate of implausible UFO reports, physicist Enrico Fermi posed the seemingly innocuous question that since the sheer scale of the universe indicates that it should be teeming with life, how come we’ve never encountered any evidence of its existence?
This question is what we now know as “Fermi’s Paradox:”
There are somewhere between 200 and 400 billion stars in the Milky Way alone. There are perhaps 70 sextillion (7×1022) in the observable universe. With numbers this big, even if life is an extremely rare phenomenon, there would still be enough life-bearing planets for technologically advanced civilisations to emerge in large numbers. And since the universe has been around for a long time, a reasonable proportion of those civilisations could be expected to be far in advance of their own. Given the numbers, we would anticipate that our solar system should have already been visited by space aliens. But even if we were somehow by-passed, our own observations ought by now to have yielded evidence of alien communication, or the evidence of non-natural structures such as orbiting space stations.
For a moment this week, it seemed like humanity had for the first time stumbled across precisely the kind of evidence that would put Fermi’s Paradox to bed. Might it be that the reason we had not discovered alien civilisations was that we had merely been looking in the wrong place?
Sadly, it turned out that NASA had taken a leaf out of the fake news playbook when they announced their Wednesday 22nd February press conference, but failed to say what they had discovered. This – predictably – led to the rapid spread of social media rumours that they had discovered evidence of intelligent life on a distant world. While this undoubtedly fuelled interest in the press conference, it had the negative effect of making a really important scientific discovery – of seven earth-sized planets in the TRAPPIST-1 system – something of a come-down. We wanted space aliens and they gave us barren planets!
As it happens, three of the planets are inside the “Goldilocks zone” where water could exist as a liquid; something believed to be an essential precondition for life to emerge. Indeed, further study of the planets’ atmospheres will find oxygen and methane (thought to be evidence of life) if it is present. But for those who wanted space aliens, Fermi’s Pardox is alive and kicking. However, the reason for this might be as troubling as the fact that we have not encountered an extraterrestrial civilisation .
Broadly, our inability to find alien life can be answered in two ways: First, it simply isn’t there. The religious texts were correct, humanity really is unique in all of creation. This, of course, is unlikely given the numbers involved. So the alternative must be that we have been looking in the wrong places and using the wrong observation technologies. This said, it is unlikely that other civilisations would not have discovered and at some point used radio, so if the universe was teeming with life and given the distances/time involved, it is not unreasonable to expect that we would have discovered a transmission signal by now.
I am not alone in taking seriously a third explanation for Fermi’s Paradox. Climate Documentary: The Cross of the Moment argues that life creates the conditions for its own destruction; so that sustained life is much rarer than Fermi’s numbers might suggest. If this is so, then civilisation of any kind is highly implausible (consider the billions of years that Earth has revolved around the Sun without even the hint of civilisation prior to our arrival just the blink of an eye ago in universal time). Similarly, philosopher Robert Persig has argued that life itself is an affront to the laws of thermodynamics:
“Why… should a group of simple, stable compounds of carbon, hydrogen, oxygen and nitrogen struggle for billions of years to organise themselves into a Professor of chemistry? What’s the motive? If we leave a chemistry professor out on a rock in the sun long enough the forces of nature will convert him into simple compounds of carbon, oxygen, hydrogen and nitrogen, calcium, phosphorus, and small amounts of other minerals. It’s a one-way reaction. No matter what kind of chemistry professor we use or no matter what process we can’t turn these compounds back into a chemistry professor. Chemistry professors are unstable mixtures of predominantly unstable compounds which, in the exclusive presence of the sun’s heat, decay irreversibly into simpler organic and inorganic compounds. That’s a scientific fact.
“The question is: then why does nature reverse this process? What on earth causes the inorganic compounds to go the other way? It is not the sun’s energy. We just saw what the sun’s energy did. It has to be something else. What is it?
It would seem that life stands in direct contradiction to the law of entropy – that things break down not up. This would certainly go a long way to explaining why we cannot find any space aliens. However, physicist Eric J. Chaisson makes the case that despite local observations like those made by Persig, entropy works on the universal level by generating complexity. That is, it creates structures that dissipate energy ever faster:
“By utilizing energy order can be achieved, or at least the environmental conditions made conducive for the potential rise of order within open systems ripe for growth. Whether it is electricity powering a laser, sunlight shining on a plant, or food consumed by humans, energy flows do play a key role in the creation, ordering, maintenance, and fate of complex systems—all in quantitative accord with thermodynamics’ celebrated second law. None of Nature’s ordered structures, not even life, is a violation (nor even a circumvention) of this law. For both ordered systems as well as their surrounding environments, we find good agreement with modern, non-equilibrium thermodynamics. No new science is needed.”
Chaisson plots an incremental growth in the free energy rate density (the amount of free energy moving through a system) as the universe evolves over time:
“More than any other single factor, and quantitatively so, energy flow would seem to be a principal means whereby all of Nature’s diverse systems naturally became increasingly complex in an expanding Universe, including not only galaxies, stars and planets, but also lives, brains and civilizations.”
This does not imply some sort of guiding hand or inevitability. Rather, it is simply that each stage of complexity creates the conditions for the development of the next. However, this development comes at a cost. When a complex system is examined together with the environment in which it exists, it remains compatible with the second law of thermodynamics. In every case, the by-products of complexity are environmental decay, pollution and the generation of more unusable (heat) energy.
Of even more concern than this environmental cost of complexity – at least from a human perspective – is the potential for collapse. Unlikely as it may seem, the contemporary human global economy might be the most complex system ever to exist anywhere in the universe (logically, the most complex system has to exist somewhere at any point in time). This is not to assert the religious story that we are anything special. Rather, it is to raise the possibility that we stand – or more correctly used to stand – at the apex of complexity. We reached the maximum possible free energy rate density.
In the same way that successful predators consume so much of their prey that hunger and population collapse must follow, humanity burned its way through millions of years’ worth of fossil carbon in just a few short decades. In the process, we used industrial agriculture to grow the population well beyond our planet’s carrying capacity. We have used the atmosphere and oceans like a rubbish tip, to the point where both are now killing the human habitat. And it might not even be our fault! Like every other living thing, we might simply be doing precisely what Chaisson says the universe itself is doing – mobilising and dissipating as much free energy as possible as quickly as we can. Life’s survivors are merely those organisms that were able to harness energy in the most efficient way. This is why, for example, the structure of trees is recognisably similar. It is why predator and prey animals share similar characteristics (e.g. predators have binocular vision and shorter digestive tracts). It may also be why civilisations follow broadly the same track:
“What took place in the early 1500s was truly exceptional, something that had never happened before and never will again. Two cultural experiments, running in isolation for 15,000 years or more, at last came face to face. Amazingly, after all that time, each could recognise the other’s institutions. When Cortez landed in Mexico he found roads, canals, cities, palaces, schools, law courts, markets, irrigation works, kings, priests, temples, peasants, artisans, armies, astronomers, merchants, sports, theatre, art, music and books. High civilisation, differing in detail but alike in essentials, had evolved independently on both sides of the earth.”
We can readily observe that life is cyclical. Living things grow to maturity, and then they age and die. After they die, like Persig’s chemistry professor they breakdown into their constituent chemicals. These are readily reused by other organisms. And so the cycle of life begins once more. We humans have also been around long enough to observe that civilisations go through a similar cyclical process. This is why, for example, the Mayans were not around to explain why they never bothered to extend their calendar beyond 2012.
Sociologist Joseph Tainter has tracked the rise and fall of civilisations, and concludes that complexity is, indeed, the problem, and energy is, indeed, the key. In every case, civilisations overextend beyond energetic limits. In the ancient world, this meant destroying the land base that the civilisation depended upon for food and resources. Unable to conquer resources from outside or having conquered all of the available external resources, they were obliged to fall back on what they could produce annually. However, in each case, the civilisation fell because it desperately attempted to sustain that which was unsustainable – to keep the previous high-energy society after the energy was gone.
The only difference today is that we have enjoyed the once and for good accidental benefit of fossil fuels. These provided us with the energy to power an advanced technological civilisation. But they also caused us to destroy the habitat that we depend upon for our existence. Today, having burned through roughly two thirds of the recoverable fossil carbon on the planet, and having raised atmospheric greenhouse gases to dangerous levels, we face our own collapse in the shape of declining energy returns to society and an increasingly hostile environment. And like every other civilisation before us, we are engaged in a desperate struggle to find a way to sustain a civilisation that we readily proclaim to be unsustainable.
The irony, of course, is that were it not for the technological advances made possible by our access to fossil carbon, we could never have developed the complex and increasingly global education system that allowed the level of self-knowledge for us to see how we are destroying our habitat. Nevertheless, the universe is probably indifferent to the cruelty that we are perhaps unique in having foreknowledge not only of our own personal mortality, but of the imminent end of our civilisation and perhaps even our species.
This understanding takes us back to Fermi’s Paradox. Might it be that the reason that we find no evidence for visits by space aliens is that it is impossible for a civilisation to continue to exist for long enough to develop the knowledge and harness the energy required to make such an epic journey? More worryingly, could it be that very few civilisations ever mange to develop the kind of communications technology that we would be able to observe? Might civilaisation more often have collapsed back to dust without ever having discovered or used fossil carbon? Indeed, could it be that all civilisations – our own included – are destined to bring about their own energetic and environmental collapse? One thing we can say with certainty is that we have been discovering a lot of Earth-like planets in the last decade or so. But not one of them has shown even the slightest trace of the existence of an advanced civilisation. Indeed, all of the evidence we have so far suggests that our idea of a Star Trek technological future simply does not exist in this universe.
The more empty rocky planets we discover, the more we should consider that where we are now – or at least where we were at the end of the last century – might be as good as it gets. That being so, we might want to stop treating progress as inevitable and think a little harder and with more urgency about the kind of civilisation that we might be able to sustain in a post-carbon world.
As you made it to the end…
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