By Dr. Gary Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the second article in a four-part series discussing the probabilities of extraterrestrial life elsewhere in the Milky Way galaxy.
In the first part of this article series, I discussed the Drake Equation and its suggestion that the galaxy might be teeming with intelligent life. However, a major contradiction to the fundamental implications of the Drake Equation comes in the form of the Fermi Paradox, a logical quandary first observed by physicist Enrico Fermi in the early twentieth century.
The Fermi Paradox: If Extraterrestrial Life Exists, Why Haven’t They Visited Earth Already?
Fermi noticed many of the same observations referenced in the Drake Equation. Even prior to the data that Drake had to work with in 1961, Fermi speculated that there were billions of stars in the Milky Way galaxy. He also posited that many of these stars were likely orbited by Earth-like planets and that the development of intelligent life might also be fairly common as well, provided that Earth is not an extraordinary case.
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Given the age of the Milky Way galaxy relative to the time that it’s taken human beings to evolve from the first single-celled organisms to their current state, it is also probable that species of intelligent life on planets that are far older than Earth might by this time be far more advanced than humans are today. After all, look at the advancements in technology that our species has managed in just the last 100 or so years of our existence.
Imagine what we’d expect to see from a civilization that has had a thousand, or a million, or a billion more years’ time to progress. As a result, Fermi posited that some — if not many — of these earlier civilizations should be able to engage in interstellar travel.
Finally, Fermi reasoned that even at modest interstellar speeds — a small fraction of the speed of light — the entire Milky Way galaxy could be traversed in a million years or so. With that understanding in mind and given that the Milky Way galaxy is many billions of years old, Fermi arrived at the paradox which bears his name. He asked that if:
- Intelligent life is common, and
- They’ve been around for billions of years, and
- Interstellar travel is a typical accomplishment of such intelligent civilizations, THEN where are they?!
In other words, Fermi reasoned that Earth should have been ‘discovered’ by other species many times over the course of the Earth’s 4.5 billion-year history. But other than conspiracy theories about aliens visiting the ancient Egyptians or modern UFO abduction reports, there is still no credible evidence for extraterrestrial contact.
Fermi concluded that something must be wrong about the assumptions made in his paradox, or the ultimate conclusion one is led to by those assumptions, or both.
Resolving the Logic in the Fermi Paradox
Fermi’s paradoxical observation is not without criticism, however. There have been a number of different theories proposed to resolve or reconcile the problem in Fermi’s logic.
Some theories are fairly simple. For example, some experts assert that either intelligent life — or perhaps even life in general — is much rarer than the assumptions of Fermi (and Drake) would suggest. Perhaps we are alone after all.
Others argue that intelligent life might be destined to inevitably destroy itself before it ever gets far enough along in its evolution to develop working interstellar travel technology. Proponents of such theories often point to the human propensity for war and conflict — and the threat of self-destruction posed by nuclear weapons — as evidence that humans are already headed down such a path.
Still other theorists propose that we humans haven’t been around long enough — on the cosmic timescale — to notice other life or be noticed ourselves. There are also more extreme theories, such as the idea that Earth is being intentionally isolated as some sort of social experiment by another form of life, also known as the “planetarium hypothesis.”
Whatever the actual explanation, Fermi presented a very interesting challenge to the idea that intelligent life is abundant throughout the Milky Way galaxy. This idea is one that we’ve been wrestling with for the better part of a century without any clearer an understanding than when the question of whether or not extraterrestrial life exists was first raised.
The lonely implications of the Fermi Paradox haven’t stopped us from looking for life elsewhere in the galaxy, though. In the next part of this article, we’ll look at mankind’s efforts to find extraterrestrial life in the Milky Way through the Search for Extraterrestrial Intelligence (SETI) program.
About the Author
Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.
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