Every day, the odds of us finding life elsewhere in the universe seem the go up, with the continuous discoveries of exoplanets in the habitable zone, and the abundance of organic molecules and elements throughout the galaxy. It should be any day now that we find extra-terrestrials. So in the apparent abundance of real estate for life in the universe, we run into a huge problem: Where is everyone?
This is a long standing problem in modern astrophysics, and it’s called the Fermi Paradox, after twentieth century physicist Enrico Fermi. So far, we haven’t come across any evidence in our search for life elsewhere in the universe, let alone intelligent civilizations. If life could evolve on this planet, and if life is a necessity of the proper conditions, then why can’t we hear anyone else out there in the universe on our radio telescopes? Why have they not come to say hello (though some conspiracy theorists would argue that they have.) Why do we not see civilizations all over the galaxy? Moreover, why is the galaxy not completely colonized at this point?
First, let’s gander at the less exotic answers to the question.
We haven’t been searching long enough
In the grand scheme of things, we haven’t been looking for ETs for very long. We’ve only been space-faring for about half a century, and SETI (Search for ExtraTerrestrial intelligence),which searches for radio signals from intelligent life, has existed for even less time. We’ve come up with nothing thus far, but there’s plenty of space to look, and a few decades of searching is likely to yield little, if anything at all. In the cosmic perspective, we’ve barely set foot out our front door, and we live in the middle of nowhere.
Intelligent life is rare
Our planet has existed for over four billion years, and it took that long for a civilization to come about. We’re the first species to invent radio, leave the planet, and look for extraterrestrials. Even now we’re only one of millions of species on the planet, which represent less than 0.01 percent of all the species that have ever lived on this planet. Perhaps life is abundant throughout the universe, but we don’t notice it because intelligent and civilized life could be much more unique.
Humans were lucky, though. Not only do we have the intelligence to investigate the world around us, but also the means to do so: our hands. The dexterity of our hands evolved with the use of tools, and has allowed us to manifest our intelligence by building cities, vehicles, space craft, and radio telescopes. It’s not inconceivable (though very difficult to verify) that some species in this planet’s history have gained some level of intelligence and started asking questions about their place in the world (some would argue that there are species on earth now, other than humans, that possess such intelligence). They may just not have had the ability to manifest their intelligence by manipulating their environment, as we do.
Life itself is rare
On a similar note, it could be that life does not come about so easily. Perhaps earth is a lucky draw in that life exists here at all. It’s hard for us to tell exactly how rare life is until we find life (or search far enough without finding it). The only life we can look for outside of our solar system would be life that has emitted radio signals for us to hear. Unintelligent life that exists out there in the universe, we may not know about for a long, long time. If ever.
Intelligent life is bound to be more rare than life in general, so any rarity you apply to life would only be confounded on the possibilities of intelligent life.
The universe is a damn big place, not just spatially, but temporally. This does have to do with the rarity of life, as statistically, civilizations would tend to be evenly distributed. If they are rare enough, then perhaps they are far too distant for their radio signals to ever reach us.
It’s also unlikely that we would be on a same level technologically as another civilization at the same point in time. We would either be far behind them or very much ahead of them. If radio is a system of communication used for a short period of a species’ history, then we would have to be listening at the right time. Perhaps radio signals from other civilizations have passed by our planet while we weren’t paying attention…
The “Great Filter”
This idea suggests that life has certain developmental road blocks to pass through in order to reach a highly civilized and technological state. The birth of life, disease, nuclear war, or some combination of these could be a roadblock that every civilization would have to get through in order to have a presence in the galaxy (or beyond). If the filter is sufficiently difficult to pass through, then the rarity of civilizations increases. Perhaps we’ve passed ours. Perhaps we have yet to do so.
Life tends to destroys itself
Similarly, it could be that the tendency of life is to destroy itself. We nearly experienced this several times throughout the Cold War between the United States and USSR. Nuclear weapons could still destroy us very quickly, or if not, weaken us to a point where we would be more susceptible to extinction.
Moreover, the way that a civilization interacts with it’s environment could influence it’s future prospects. Climate change and global warming, though likely not fatal to us, could bring us to our knees sufficiently that we would not have the resources to expand outward. (See the Atomic Clock at the Bulletin of the Atomic Scientists.)
More Exotic Answers
Life is hiding from us
Perhaps we have found any evidence of extra-terrestrial life, because that life is deliberately hiding from us. This is similar to the Prime Directive in Star Trek, which forbid the United Federation of Planets from interfering with the development of a species up to some technological threshold. As a young civilization that has hardly left its planet, could aliens be avoiding us so that we can finish our own development?
They don’t use radio
Primarily we look for life by listening for radio signals, but what if highly advanced civilizations don’t use radio, but some other, more efficient form of communication? We don’t really know what that form of communication would be, but it is a hypothetical explanation.
We have discovered life, but it is being covered up*
Let me be as careful as possible when I write this. We have run into the realm of conjecture and fantasy plenty already, so why not go a little further? Conspiracy theorists believe that aliens have visited us, or are among us at this very moment. However, the overwhelming scientific community does not think this is happening. Always, always be skeptical in the face of conspiracy theorists. Covering something such as an alien visitation up would be unlikely. Any sufficiently advanced civilization would likely either have it that absolutely everyone know they visited, or no one know. Not some small, less reputable minority. It is certainly plausible, but evidence is necessary to back up something like this.
Having said that, consider the sci-fi story 2001: A Space Odyssey. In the book adaptation, it is made clear that the individuals that are involved with the discovery of the monolith decide that proper conditioning would be needed prior to announcing the discovery. Do you think once we make find evidence of ET’s, we will be told immediately, or would it be a fact slowly, and carefully released to the public? I’m sure it would depend on who made the discovery…
Are we alone?
The last situation I will address is an eerie plausibility; that we are completely alone in the galaxy, or the universe. Galaxies are far enough apart that if there is no other life in our galaxy, we may as well be alone. Again, it’s hard to gauge the possibility of this, as we don’t fully understand the mechanisms that spark life in the first place, but maybe against impossible odds, or some combination of the above possibilities, we find ourselves in a universe completely uninhabited by anyone other than us. What if such is the case? Well that means that everything is left to us to explore, and maybe we could use the opportunity to ourselves populate the universe. That all depends on our future.
The Drake equation
I’ll close with this. In the early sixties, Frank Drake came up with an equation to predict the amount of alien civilizations in any given galaxy, based on a few variables. We can’t take full use of it, because we don’t know what the variables really are, but play around with the math a little bit, and see what possibilities you can come up with:
- N = the number of civilizations in our galaxy with which radio-communication might be possible (i.e. which are on our current past light cone);
- R* = the average rate of star formation in our galaxy
- fp = the fraction of those stars that have planets
- ne = the average number of planets that can potentially support life per star that has planets
- fl = the fraction of planets that could support life that actually develop life at some point
- fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
- fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
- L = the length of time for which such civilizations release detectable signals into space
What do you think? Are we alone in the universe? Is there undiscovered life all around us? Share your thoughts in the comments below.