There is a question that makes humanity wonder for a long time yet our scientists are still unable to find the answer for. This question is: do aliens exist?
The first thoughts about aliens were probably made up by the ancient Greek philosophers, the Epicureans, during the first-century. More importantly, one of their poems, written by Lucretius, says nothing in the universe is unique and alone and therefore in other regions there must be other earths inhabited by different tribes of men and breeds of beasts. Our curiosity has been raising ever since, only the shape of these creatures were changed in our imagination.
So, what about the ‘modern’ aliens then? In the last century, we have been trying to locate someone or something out there but sadly, we haven’t found anything so far…
Is it really that bad we haven’t found the green men yet?
Let’s start from the beginning.
Is extra-terrestrial life even possible? Long story short, yes, it is. Actually, the possibilities are infinite. Think about the size of the universe.
Planet Earth is one of the 8 planets of the solar system.
The solar system is one of the 100,000,000,000 stars in the Milky Way.
Is it not big enough yet?
The Milky Way is part of The Local Group with 50 other galaxies. This region is about 10,000,000 years in diameter. It is so big that we probably will never be able to leave it no matter how advanced our technology will become.
However, The Local Group is only one of the hundreds of galaxy groups in the ‘Laniakea Supercluster’.
Moreover, our Supercluster is only one of the millions of superclusters that make up the observable universe.
We know planets are common in every system, furthermore, NASA has found 3,775 Earth-like planets so far and there is more coming.
We also know that a fifth of the 20,000,000,000 sunlike stars in the Milky Way have got an earth sized planet in their habitable zones where Earth is.
If we assume there is life on 0.1% of these planets, we have estimated exactly 4,000,000 alien lives. If we take the age of the universe into account, this number is even higher.
A bit of maths might make us feel life is quite common in the universe, doesn’t it?
So, where are they? Why can’t we see them? Unfortunately, nobody knows and this leads us to the Fermi Paradox, a theory that builds up on a group of filters.
Ever played SPORE? If not, imagine these filters as a flight of stairs in which every step shows the level of evolution. On the very bottom, we find bacteria and all sorts of simple life. The higher we go, the more complex life we encounter until we meet species that evolve brains, enabling them all sorts of skills such as forming culture, building tools, creating religions, etc. You probably realised these species are us and there is only one of them on the Earth.
On the upcoming steps, this race becomes the dominant lifeform on its own planet and attempts to leave and colonise other places. This is the rule of evolution. For a race to survive, it must spread to as many places as possible. It’s highly likely that this is the goal for every intelligent life as we can see this process on every animal on our planet.
Since we can’t see anyone, regardless the numbers, we could assume there is a filter stopping every advanced alien lifeform. And this filter might be the step ahead of us. This is what astronomers call as ‘The Great Filter’. There are two scenarios:
Scenario 1. – The filter is ahead of us.
Think about the dinosaurs. It wasn’t their fault they died, was it? Such a natural disaster can happen to us as well. In fact, it could happen any moment.
However, The Great Filter is not a natural disaster that would stop us for a good thousand years. It would stop us for good, like the dinosaurs.
Our technological advantage could make our odds even worse. Stephen Hawking stated many times how dangerous artificial life can be and gave voice of his worries about nuclear weapons.
The Great Filter might be the level of technology so high we can’t handle, thus it would destroy us no matter what we do. Unfortunately, our odds look very bad at the moment and if we find life beyond Earth it would be even worse.
Every found complex organism would mean the filter is in front of us. The more intelligent life we find, the higher the chances for this scenario.
Scenario 2 – The filter is behind us
If we passed the filter already, the galaxy is likely to be empty. This might sound very depressing for sci-fi fans and those who are hoping to find Martians anytime soon but it also means our race has got the chance to become the first (or maybe only) dominant race in the galaxy, if not the universe.
Imagine billions of planets, waiting for us and no one else. Beautiful, interesting, mysterious and amazing places. All of them for us because we are special.
This scenario brings an interesting question though, where is the filter? Is it the level where a complex lifeform is born? For now, we don’t know how that happens, but it did happen on Earth. Perhaps this is what makes us so special. Could it be because of our brains? Maybe we’re just lucky because we haven’t got wiped out by any huge natural disasters.
Needless to say, The Great Filter is only a theory. We have been searching for intelligent lifeforms for only half a century, maybe there is someone waiting for our call, we just have to wait. And what if we’re not advanced enough to find extra-terrestrial life yet? Maybe these questions will never be answered.
For now, we must keep the focus to ourselves and enjoy this perfect time of our storyline when we are able to make such big and fascinating thoughts. The best way to find out where we are on the staircase is to leave Earth and start colonising other places. NASA’s Mars project sounds promising.
All things considered, our future is not as hopeless as The Great Filter suggests…
…If we found space travelling aliens they would probably kill us anyway like in every Hollywood film. Good day.
Into the Universe with Stephen Hawking, directed by Stephen Hawking (Discovery Channel, 2010)
Kurzgesagt – In a Nutshell
M. Cirkovic and V. Mikosevic-Zdjelar ‘Extraterrestrial Intelligence and Doomsday: A Critical Assessment of the No-Outsider Requirement’
NASA Exoplanet Archive
Nick Bostrom ‘Where Are They? Why I Hope the Search for Extraterrestrial Life Finds Nothing’