When I was a teenager, I was convinced that aliens were here. It seemed completely plausible to my 13-year-old self that humanoid creatures from other planets could be visiting us in strange, saucer-like spacecraft. After all, look at all these people on the internet! They can’t be lying! There may have been some influence from my obsession with David Duchovny on The X-Files… but I digress.
As you can imagine, today I find the visitation of Earth by “little green men” to be extremely implausible. UFOs and alien visitation have occupied skeptical discourse for decades, as a quick glance at the archives of a publication such as Skeptical Inquirer will reveal. The more interesting question to me is: Why aren’t They here?
Famed physicist Enrico Fermi asked this very same question in 1950 around the lunch table at Los Alamos National Laboratory. Discussing a recent New Yorker cartoon in which saucer-flying aliens are carrying off New York city trashcans (I still don’t get it), Fermi set off a historic conversation by asking his colleagues, well, where ARE the aliens?
Here is the justification for his surprise: If you just look at our little corner of the cosmos, the Milky Way Galaxy, we have 100 billion stars, and the Universe has been around for over 13 billion years. After about 5 billion years of star-formation history, enough “heavy elements” like carbon, silicon, and oxygen, required for planet formation and “life as we know it” should have been available to start making planets. Our planet was formed another 3 or 4 billion years later, so there may have been planets that had a huge head-start on us in regards to time to form life.
Assuming the “Principle of Mediocrity,” or the idea that there is nothing necessarily special about the Earth, shouldn’t life have arisen elsewhere? Even if sentient life is a one in a hundred million chance, that gives us approximately 1000 civilizations, or one every few million years. Homo sapiens is only 150,000 years old. Given millions or billions of years, a sentient race should have colonized the Galaxy by now! So… why aren’t we inundated with visitors from another world? It’s a disquieting notion when you stop to think about it.
The possible answers to this Fermi Paradox* fall into three main categories:
Scenario 1: They are here, but they are being discreet about it.
So, maybe the UFO-believers are on to something. Maybe the extraterrestrials are buzzing by us all the time, but they have some sort of policy of non-intervention with young species like ours. Hmmm… this sounds familiar. Star Trek popularized this idea with the “Prime Directive.” This explanation does not sit well with me because of two words.
Sexy ladies? That’s a great reason to violate the Prime Directive! I feel like it? That’s a good reason, too! In 1000 Galactic civilizations, I find it hard to believe that there are no Captain Kirks.
Plus, it’s a tiny bit self-important to think that we’ve just been sheltered all this time.
Scenario 2: They haven’t/never made it here.
It could be the case that life is easy to create. It may even be plausible for sentient life to have formed several times, despite the challenges. That doesn’t necessarily mean that our extraterrestrial cousins wanted to spread out and colonize, though that notion may seem alien to us. There is also the distinct possibility that these civilizations never made it through their technological adolescence without exterminating themselves. Or, maybe interstellar travel REALLY is that hard to do. That’s right, no warp drive, fellow Trekkies.
Scenario 3: We are really the first sentient species in the Galaxy.
Well… damn. This is not very positive, especially for supporters of various SETI programs, but we have to acknowledge the possibility that we might be the very first sentient, intelligent, traveling, communicating beings, at least within the reasonable distances of our Galaxy and that is why we have not yet made “first contact.”
This is a topic that has fascinated people for decades, and we could easily amuse ourselves arguing the different sides for a long time. (In fact, I taught a whole college course on this!) We now know that planets are everywhere and that the building blocks of life litter the Galaxy. But then… where is everyone? Why do we still seem so alone? Until we find evidence of extraterrestrials, or until we colonize the Galaxy ourselves, I don’t think we can properly answer this question. But is fun to speculate.
Thanks to everyone who commented on my last post, referencing this idea in some way! I have to give much credit also to Bob Rood, recently deceased astronomy professor at UVa and creator of the “Life Beyond Earth” course, and to Ed Murphy, current professor at UVa, for mentoring me through this fascinating topic as I prepared to teach it.
*It might be more accurately called the Tsiolkovsky-Fermi-Viewing-Hart Paradox, since it was discovered independently four different times.