Have you ever looked at the stars and wondered who else is out there??? Coz I have. Looking at the night sky is not only calming but it often fills people with a feeling of vastness. More often than not my star gazing ends in me thinking, damn where are all the aliens at??
Are we (earth lifeforms) the only living things in the entire universe? Lets take a look at some numbers:
The radius of the observable universe is 45 billion light years. The current estimate is that there are approximately 100 billion galaxies in the universe with 100-1000 billion stars each. So shouldn’t the universe be teeming with spaceships?
That’s clearly not the case. But Why? That’s exactly what Italian physicist Enrico Fermi wondered and this is called THE FERMI PARADOX. The fermi paradox is basically “the apparent contradiction between the lack of evidence and high probability estimates for the existence of extraterrestrial life”.
So why don’t we have aliens knocking on our doors?
Firstly because even though the universe is humongous (still an understatement) we will never be able to travel past our galactic neighborhood, the milky way (unless we can warp time and space but that’s a whole another topic trust me! *sighs*). Even in milky way there are a total of 400 billion stars out of which there are 20 billion sun like stars.
Out of those 20 billion sun like starts 1/5th have earth sized planets around them…..even if 0.1% of those earth sized planets have life……we should still have 1 million planets with life just in our milky way! So again the question remains…..why haven’t we been visited by our alien neighbors or do we even have any?
Well we might have just missed them….The universe is 13 billion years old (thank you big bang) and the earth is 4 billion years old. Things only started becoming habitable in the milky way around the time earth was formed but still there could have been other planets in which life started lets say 5,6 or 7 billion years ago. But given that human life on earth has only existed for about 200,000 years, a mere fraction of the time of earth’s own existence we could have already been visited by ancient alien civilization(s) and missed them.
Just coz we weren’t home (earth) for most of the time doesn’t mean no one came knocking at the door…..so why don’t they come again? Well they just might IF aliens exist at all.
Ever heard of THE GREAT FILTER? It’s an argument that states that complex life is hard to develop because of probability threshold. Imagine how many events in the universe had to go just right so that the human (intelligent life) could exist! The great filter argument states that because the probability of things going just right in all the right places for complex life to develop are extremely low this might work as a barrier to the evolution of intelligent life.
Earth has witnessed great filters in the past, for example past mass extinction events and even when it was formed. What’s scary is that some great filters might lie ahead of us. A great filter in the future could be mass extinction event of our own doing (destruction by advanced AI, biotechnology or self-replicating nanobots) that might prevent us from becoming a space colonizing civilization……our neighboring planets might have dealt with great filters such that life on those planets 1) could never develop, 2) could never develop into intelligent form, 3) Might have been eradicated by mass extinction or 4) might have self-destructed due to extreme technology gone wrong.
So right now we really have no evidence that life exists anywhere besides earth. That makes things even more precarious in the sense that it’s up to us humans to keep the flame of life going. If we are the only life in the universe, we have to survive for there to be any life at all and for there to be a probability that we might one day be the space colonizing aliens we think are out there.