What is the Fermi Paradox?
The Fermi paradox relates to the presence of other intelligent life in the universe. Put simply, if there are billions upon billions of stars in the universe, and if a certain percentage of these stars should have planets that are suitable for developing intelligent life, then “Where is everybody?” The paradox is the difference between the overwhelming probabilistic evidence in favor of intelligent life developing and the complete absence of evidence that this is the case.
Propositions of the Fermi Paradox
- There are billions of sun-like stars in the Milky Way galaxy. Many of these are billions of years older than our own star.
- There is a high likelihood that many of these stars are orbited by earth-like planets. Thus, it stands to reason that at least some of these planets have developed intelligent life.
- Since the life on our planet is seeking to develop interstellar travel, it’s likely that some of these other planets have developed civilizations capable of interstellar travel.
- Even if interstellar travel is limited by the speed of light, then our galaxy could be traversed and colonized within a few millions of years.
While some millions of years may seem like a huge amount of time, it’s not all that long on a geological scale, much less a cosmic scale. So, with billions of years to develop and millions to travel the galaxy, we should be able to see some sign of other life in the galaxy.
Mathematics of the Fermi Paradox
The mathematics go as such: Our galaxy alone holds between 100 and 400 billion stars. And our galaxy isn’t the only one in the universe. In fact, there are estimated to be as many galaxies in the universe as there are stars in our own galaxy. It must be remembered that much of this is estimated based on what we can see of the universe around us. However, this would amount to at least 1022 sun-like stars with the potential of life-bearing planets.
Scientists believe that life can only develop in the “Goldilocks region.” This is a habitable zone far enough from the sun to prevent complete burn off and close enough to prevent a complete freeze. That’s why it’s called the Goldilocks zone – it’s neither too hot nor too cold. Water, the most essential component for life, will be able to exist in liquid form on these planets. It’s estimated that from 22-50% of all sun-like stars will have planets orbiting them in this region. This means that about 1% of all stars in the universe should have earth-like planets orbiting them.
1% doesn’t sound like a lot, but on a cosmic scale it comes to 100 billion billion planets. 1020 earth-like planets with the potential of developing life. Add to that the estimate that only 1% of these planets are likely to develop intelligent life capable of creating technology to traverse the stars. We’re still left with 1018 potential forms of intelligent life roaming the universe. That’s billions upon billions of civilizations that we’ve seen no sign of in all the time that we’ve been scouring the stars.
Intergalactic travel might pose more than a few challenges to travel, so it’s helpful to shrink the scale and consider this galaxy alone. And, considering only the Milky Way galaxy, this leaves us with about a billion earth-like planets. Considering the percentages laid out above, this leaves us with 100,000 other potential space-faring life forms. Plus, a good many of the other suns and earth-like planets in our galaxy are far older than our own. With this in mind, it’s likely that civilizations developed on these planets will be far in advance of our own. This means that at least some of them should be travelling the galaxy and open to observation.
There’s no real way to estimate how many of these planets might develop intelligent life, and thus how many of those planets might develop an intelligence capable of spanning the stars. However, the conservative estimates still leave us with such an astronomical number that it bears the question, “How come none of them have been detected yet?” Why have we seen absolutely zero evidence of any intelligent life in the universe except for ourselves? In the words of Carl Sagan, “If we are alone in the universe, then it is an awful waste of space.”
History of the Fermi Paradox
The name of the Fermi Paradox is the result of a lunch conversation held at the Los Alamos National Laboratory in 1950. The members included Enrico Fermi, Herbert York, Edward Teller, and Emil Konopinski. All of them were astrophysicists at the laboratory, and the discussion was about the presence of extraterrestrial life in the universe. However, the discussion had ranged on to different topics until the point that Fermi suddenly asked, “Where is everybody?” Bringing the subject back to extraterrestrial life, he followed the question with some calculations like those described above. His conclusion was that, given the probabilities, we should have seen extraterrestrial visitors often and long before then.
The Drake Equation
The Drake Equation is closely associated with the Fermi Paradox. Postulated in 1961 by Frank Drake, this is an equation that evaluates the potential for alien life based on several factors. These factors include:
- Galactic rate of the formation of stars,
- The percentage of those stars that are sun-like or capable of bearing habitable planets,
- The average number of habitable planets per star,
- The percentage of those likely to develop life,
- The percentage of those with life likely to develop intelligence,
- The percentage of planets with intelligence likely to develop technology capable of interstellar communication,
- And, the length of time that these civilizations will be able to be detected.
Multiply these factors together, and you’ll get the number of civilizations that we are likely to be able to perceive in our own galaxy. This equation applies only to those civilizations within the Milky Way, as signals from other galaxies will be too far away for us to perceive. Plus, the last four terms are entirely based in conjecture. We can theoretically assume the percentages based on what we now know of the world. However, given the amount of conjecture involved in the calculation, the numbers are nothing more than presupposition.
The Great Filter
One of the central theoretical concepts used to explain the Fermi Paradox is the Great Filter. This is the idea that developing life is faced with a certain filter that few life forms are able to pass. The nature of the filter itself is widely disputed. Some say it’s abiogenesis. Some belief that it’s the transition from single-celled life to multicellular life. It doesn’t end there. In our own history alone, other possible filter points are the development of intelligence and the development of civilization and technology. But this is just the beginning.
It’s just as possible that the human race has not yet encountered the Great Filter. It may be the point at which we develop the capacity to fulfill our needs without destroying the planet. Or to overcome our planetary boundaries and extend out into the solar system. And these are just the few that we can perceive given our current state of development.
The importance of this concept is that it gives us a theoretical perspective on the development of human civilization relative to other civilizations. We are either the first to pass the Great Filter, in which case we are lucky beyond measure. We have won a cosmic lottery, and other civilizations, should they pass the filter, will have to deal with us as the most ascendant race. If we are a close runner up, which is equally unlikely, then we will be forced to deal with the race before us. Finally, if we have not yet passed the filter, then we have an intense challenge before us, such that we will more likely fail the challenge than pass it.
Potential Explanations for the Fermi Paradox
The Fermi Paradox has been around for nearly half a century, so many theorists have tried to provide an answer. Possible explanations are hotly contested by theorists and range the full spectrum. We’ll just provide a few of the explanations in this article:
There is no other intelligent life in the universe
The calculations of the Fermi Paradox assume that the conditions on earth and in our solar system are fairly ordinary. This is termed the mediocrity principle. It assumed that the development of life and habitable planets is a common factor in the universe. But it might be something unbelievably rare. In addition to the Goldilocks zone, we have gas giants that block meteor strikes, an unusually-sized moon that influences tidal flow and plate tectonics, atmospheric and lithographic factors, a specific chemical composition to the planet, etc. These conditions may be so rare that no other life has yet developed, at least in this galaxy. Perhaps no other life exists in the universe.
If life does exist, then perhaps it hasn’t been able to develop intelligence. The jump from single cells to multicellular life is fascinating in itself. Taking it to the next step is just as unlikely. Even if life has developed on multiple habitable planets, there’s no reason to assume that this life has developed intelligence. And, to take it one step further, even if life has developed, there is no reason to assume that this life has developed technology in any way that we can detect. The Fermi Paradox assumes that intelligent life will attempt to colonize the galaxy. This might perhaps be an unwarranted assumption, based in the tendency of humanity to dominate and colonize its surroundings.
Life is prone to destroying or being destroyed
The great filter factors into this perspective, but it’s only a part of it. Perhaps life faces some hurdle that makes it unlikely for species to survive to the point where they can traverse the stars or communicate with advanced technology. It’s also possible that galaxies themselves face periodic extinction points just as we have faced on earth through geological periods. However, it is equally likely that the development of advanced technology leads nearly inevitably to the destruction of the species which has developed it. Alternately, a species which has developed advanced technology might be destructive by nature. If this is the case, then they may seek out and destroy other species that have the potential to become competitors. In the first two cases, there would be few species if any who have the capacity to traverse the stars. In the last case, then it is likely that the first species to emerge would destroy all others before they could make their presence known in the galaxy.
Species are too far separated in space or time to encounter one another
When you think about it, humanity has only been searching the stars for less than a century. This is such a small amount of time, on a cosmic timescale, that it’s no surprise we haven’t encountered another race. We are separated from other stars by light years. And this means that the journey between stars will take much longer than that. Centuries, if not millennia. Even if it were only probes sent our between stars, the millennia between stars might prevent a civilizations such as ours, developed to this point in technology over only the last few hundred years, to detect any signs of other life. Add to this different origins and times of development, and we may either develop before or after such contact might be possible. Given the vast distances, it may also be unfeasible, in terms of resources or the length of human life, to travel from one star to the next.
Races are there, but we are not receiving communication from them
We typically assume that other civilizations will be detectable through radio signals. However, other civilizations may not use these forms of communication. Or perhaps they broadcast on signals so fast or slow that they are not in the range that we monitor, or do not form comprehensible signals in the range that we understand. Plus, it’s possible that other races, should they exist, are monitoring, but not broadcasting. This is made even more likely by the possibility that other races might be aggressive. It may be dangerous to communicate with other races. It’s even possible that extraterrestrial races choose not to or are prevented from communicating with us, for reasons unknown.
The explanations of the Fermi Paradox as given above are just a few of the possibilities. And, as is apparent, they are shaped by the same supposition that characterizes the paradox itself. When reaching into the unknown, there is always the x-factor, the thing that we don’t know that we don’t know. This is the greatest criticism of the Fermi Paradox. Since all of these calculations are based upon estimates, there are so many “if’s” involved that any calculations we arrive at are no more than ideas. So, though the calculations of the Fermi Paradox are compelling, they still tell us nothing about the real possibility of life in the universe.