If the universe is nearly infinite and unimaginably old, it seems likely that intelligent life should have developed somewhere besides Earth. But where is it?
The Milky Way galaxy alone contains 100-400 billion stars, many of which are orbited by planets. On a larger scale, scientists estimate that there are approximately 2 trillion galaxies in the observable universe. Additionally, the universe has existed for approximately 13-14 billion years.
Looking at these numbers purely mathematically, it’s almost statistically impossible for humans to be the only intelligent life in the universe. In fact, life should be common in the universe, even without faster-than-light-speed travel; an intelligent species should be able to colonize entire galaxies within millions of years. Yet we see no evidence that other species exist. No communications, no radio signals, no megastructures, no spacecraft, no cities among the stars, no landings.
This begs the question, where is everyone?
This is called the Fermi Paradox, and there are many theories attempting to answer this question.
The first and easiest explanation is that humans are the only intelligent life in the entire universe. Life emerging from nothing seems impossible. Putting aside religious beliefs and theories on creation, it is extremely rare for something to form out of nothing. Scientists still don’t fully understand what the catalyst was that turned simple elements and compounds into something living. But it clearly happened here, so why hasn’t it happened on some far-off planet?
Another, more ominous theory, is The Great Filter. Essentially, the theory suggests that somewhere between nothing and becoming a galactic civilization, there is a deadly obstacle or filter that prevents life from excelling any further. It could be anything from life even forming in the first place, to nuclear wars, AI, and light-speed travel. Who knows. We could be past the filter, or it may still be somewhere in front of us.
One common theory is the “zoo hypothesis.” This theory argues that there is intelligent life out there, but they are deciding not to interact or come into contact with us. They may be watching and observing our species. Waiting until they think we are ready for them to reveal themselves.
A popular theory among conspiracy theorists and other more radical thinkers is that humans are living in a simulation. This would technically suggest that there is another intelligent species in our universe, we are just unable to interact with them. Any alien life we could interact with would also technically not be real, just another creation in a simulated environment.
Alien life also could have existed in the past, but has long since become extinct. This could be for a lot of reasons, like climate, war, disease, or just bad luck. They could still exist as well, but by using technology, we cannot detect quantum communications or Dyson spheres that block light from their stars.
One of the problems with identifying alien life is that it is probably completely different from how we represent it in movies. The form that life takes on other planets may exist completely beyond what we are able to imagine. We might not even know we are looking at an alien, even if they were right in front of us.
It’s kind of sad to think we might be the only intelligent life in the universe. In a place so vast, it would be nice to know that we aren’t alone, that maybe someone else out there has wondered about us, too. But maybe being alone is what makes our existence so special. If we really are the only life out there, then maybe it’s our job to explore the universe and spread life across the stars so we won’t be as alone.
