Italian physicist Enrico Fermi calculated that there must be intelligent life on other planets. But without any evidence he asks “Where is everybody?” Learn more about the different explanations of this paradox.
If you only read one article about the fermi paradox, this is the one to read. Writer Tim Urban published this article on the website WaitButWhy.com explaining the fermi paradox in depth. I would recommend reading the article in full, but just to give you a basic understanding here are the main points:
As scientists started learning more about how large our universe is and how many stars and planets there are, they started to calculate the number of habitable planets in the universe. Physicist Enrico Fermi calculated that there might be as many as 100 billion Earth-like planets. With a conservative estimate that at least 1% of these planets would have developed intelligent life, the Fermi paradox wonders “Where is everybody?” Many of these Earth-like planets have been around A LOT longer than Earth, so if interstellar travel is possible, wouldn’t we have been visited by now?
Scientists have broken down civilizations into three types. Type 1 civilizations use all of the energy of their planet (we are almost at this level). Type 2 civilizations harness the energy of their host star. And type 3 civilizations access energy from the entire galaxy. The scientists speculate that there should be at least 1000 type 3 civilizations by now. But there is no evidence of this. “Where is everyone?”
Many theorists and scientists have tried answer the question posed by Fermi. Here are some common explanations:
– There are no signs of higher (Type II and III) civilizations because there are no higher civilizations in existence. It’s possible that life is being formed as much as we’ve calculated, but life is not progressing into type 2 or 3 because they are being filtered out by evolutionary hurdles.
-Type II and III intelligent civilizations are out there—and there are logical reasons why we might not have heard from them. In this explanation it’s possible that the intelligent life already visited earth millions of years ago. Or maybe the civilizations are not interested in exploring for fear of death.
The question is very puzzling, and I would recommend reading Tim Urban’s full piece.