Before Unstructured Musings, I had a website called The Lair o' Lias. One of the sections of the site was dedicated to the Fermi Paradox. Thanks to the Wayback Machine, from the Internet Archive, I've been able to salvage the content of it. I thought it would be a good idea to post it to the blog. I'm breaking it into sections starting with this, the introduction.
Are we alone in the universe?
This is one of the greatest mysteries of our age. Clearly our intuition suggests that we aren't alone. It's hard to look up at the sky and to contemplate those hundreds of billions of stars in our galaxy alone without thinking that there simply must be intelligent life out there somewhere — probably life that we could communicate with if we only knew where to look and how to listen. Certainly this has been one of the great themes in Science Fiction. Over the last century, ever since H.G. Wells wrote The War of the Worlds, our media has been flooded with speculative stories that reflect our hopes (and fears) for the existence of alien life.Venus
In 1961 the noted astronomer Dr. Frank Drake came up with an equation, later to be known as the Drake Equation, which set definite parameters on how many extraterrestrial civilizations should exist. The Drake Equation asks several questions:
- How many stars are there in the galaxy?
- What fraction of those stars have planets around them?
- What fraction of those planets are capable of sustaining life?
- What fraction of those planets actually have life?
- What fraction of that number have intelligent life?
- What fraction of intelligent life forms are able and willing to communicate?
- How long do such intelligent, communicating species live (on the average)?
The beauty of the Drake Equation is that if you plug in numbers to all of its variable, you get a good estimate of how many intelligent, communicative species should exist in the galaxy at any one time. Unfortunately, this is easier said than done. Some variables, such as the number of stars in the galaxy, are easy to come by. Some, such as the number of stars with planets, can be only be approximated from educated guesses. Some, such as the fraction of biospheres that develop intelligence, are the subject of raw speculation. In spite of this, the Drake Equation generated a great deal of hope in those who wanted to believe in the existence of extraterrestrial intelligences for the simple reason that all but the most pessimistic estimates indicated a galaxy that was absolutely teeming with vocal ETIs.
SETI, the Search for Extraterrestrial Intelligence, was founded on the basis of that optimism. If you had asked the attendees at the first SETI conference to guess how long it would take before we discovered a signal, I'm confident that most would have guessed that we would do so within the space of a few years. I'm equally confident that none would have dared suggest that we would never find such evidence. Forty years later, we find ourselves confronted with a lingering silence, punctuated by several false or unconfirmable signals, and a muted sense of optimism. Most people still believe that we will find other intelligences, but there is the deep question of why, if life is as common as we suspect it is, we haven't found it yet.
The great physicist Enrico Fermi was one of the first people to ask this. Certainly he was the one who put it most succinctly: "Where are they?"
More formally, if intelligent life is as common as the Drake Equation tends to lead us to believe, why isn't its existence so obvious as to be unmistakable? Indeed, why isn't it already here?
This is the Fermi Paradox: If extraterrestrial intelligence is as common as we believe it should be, its presence should be obvious and unmistakable. It isn't. Hence the paradox.
It is a question that bestrides the question of our place in the universe. Where are they? There is a certain temptation to resist asking it, to dismiss it as premature and unworthy of consideration.
And yet… and yet…
Its presence casts a pall over any discussion of alien life. As much as we want to ignore it, as much as it acts as a damper to our enthusiasm, we are compelled to address it. It is a question that many people have contemplated, and it is one that has generated numerous potential answers.