Finding extra-terrestrial life on our nearest neighbour would be celebrated as one of the most important events of the last decades. It would also mean that we are probably doomed.
Aliens, little green men, ETs. Since the advent of the space age, both the scientific community and the general public has been fascinated by the possible existence of life forms outside our world. However, few people truly understand the enormous consequences this event would have for our survival as a species. For we should not fear the Martians of War of the Worlds, but the minuscule fossilised remains of the simplest creature in a meteorite. To understand why, we have to go back to a laboratory in New Mexico in 1950, where one of the greatest minds of the 20th century formulated a very important question for the first time.
Where are they?
Enrico Fermi is remembered as one of the key components of the Manhattan project, as well as for being one of the brightest physicists of all time. It is less well known that he first wondered about a matter that still haunts astronomers and researchers of extra-terrestrial life. The question is surprisingly simple: if we assume that the appearance of life on Earth is a process that can be easily replicated elsewhere, it should be very likely that millions of intelligent civilisations have arose in the Universe. There are billions of stars, and many of them have planets similar to Earth orbiting them. But then, we do not have any evidence of extra-terrestrial contact with us in our recorded history. Not a single evidence of intelligent life, not even after nearly 50 years of thoroughly looking for them in the cosmos. Where are they?
It is very hard to estimate the number of civilizations in our galaxy, let alone the entire universe. The first mathematical approximation came in 1961, astrophysicist Frank Drake first enunciated his famous equation as a way to give an estimation of said number:
Where is the number of extra-terrestrial civilizations in the Milky Way inside our ratio of communication, is the rate of star formation, the percentage of said systems that have planetary bodies, the number of planets that have the conditions necessary to give birth to life per star, the fraction of those planets that, having the proper conditions, end up supporting life, the fraction of inhabited planets that evolve into civilizations, the percentage of civilizations that show their presence by emitting identifiable signals, and the amount of time those signals are continuously released (Aguirre, 2008).
The current estimates vary widely, as nobody is sure of the actual values that can be inserted in the equation, especially with the latter parameters. We do know, though, that the first three terms are probably very large, as new exoplanets with Earth like conditions are discovered each year. This means that there must be a factor among the last four ones that decreases the number of civilizations extremely, which we call the Great Filter.
The Great Filter
The idea of the Great Filter is what makes the potential finding of life on close planets or moons like Mars or Europa so dangerous for our long term future. If microscopic life is indeed discovered, it would mean that the factor is probably large (as it would show that life could arise independently even in different planets of the same system). Thus, the Great Filter would be among the last three terms, probably in the very last. A logical consequence of this is that intelligent civilizations that develop technology that allows themselves to show their presence (e.g. radio) do it for a very small period of time in terms of geological eras. In other words, they soon die out.
What the Drake equation and the Great Filter tell us is that there is a likely chance of intelligent life destroying itself. This is not an outlandish claim; after all, current world powers have enough nuclear head to bring total extinction to the human race. In addition to that, we have not yet seen the full potential of technologies like AI that could very well become a threat to us, and we are unprepared to events like gamma ray emissions, which may already have caused a massive extinction that almost complex life 252 million years ago, at the end of the Permian.
We should not forget the sword of Damocles that is hanging onto us since the start of the industrial revolution. Climate change due to human action has already started to show its effects, and countless ancient civilizations were completely destroyed by the slightest alteration of climate patterns. Like the statue of Ozymandias, they remind us that nothing is eternal. If the Great Filter is still ahead of us, in the form that is anthropic global warming, we may very well never pass it. We will just become another silenced voice in the cosmos.
Juan Gorrochategui is studying for a BSc in Chemistry at Imperial College London
Banner Image:Mars appears as a red-orange globe, ESA / Wikimedia Commons