Are there intelligent beings elsewhere in our Galaxy? If not, where are all the Aliens? This question gives rise to one of the most profound paradoxes in history known as The Fermi Paradox.
Named after the Italian-American physicist Enrico Fermi, this paradox is one of the biggest unsettled questions in astrobiology. The idea started when, in 1950, Fermi asked his co-workers over lunch where are the extraterrestrials? If there are billions and billions of stars and probably even more planets, surely we are not the only intelligent beings in the universe. Then why we have not already been in contact with the outers?
People have debated on this for many years. Various articles and books have been published arguing if aliens do really exist, we should have been aware of them already. If we have not found any trace of life outside Earth yet, then they possibly, do not exist. Let us take a deep look into these claims and try to explore some solutions that scientists have put forth over the years.
Possiblity of life outside Earth
The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation. It suggests that even if the probability of intelligent life existing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations.
It is not the size of the universe that is important per se, but the fact that it is big enough to contain a vast number of habitable planets. We do not know precisely how many such planets are out there, but one recent estimate suggests that our galaxy might contain as many as 100 billion Earth-like planets.
The Fermi argument extends in a way by saying that it is highly likely that some of these planets will have intelligent life forms that might have developed advanced technology. But then again, we have no sign of extraterrestrial communication whatsoever.
Scientists have tackled the paradox through different scenarios based on logical reasoning. Following are a few arguments in some theories that are documented.
Problems with interstellar communication
Communication is not easy, as one would think!
SETI (Search for Extraterrestrial Intelligence) is a non-profit research organization that monitors electromagnetic radiation for signs of communication from other planets. Although it has been trying to listen for the last 6 decades, all efforts went in vain. Part of the failure lies in the fact that we have only sampled a small portion of the universe.
Let us understand this with an analogy: if you went to the beach with a glass and scooped up some water, would you expect to find fish in it? Probably not, that does not mean there are no fish in the ocean. It just means we have not collected enough water to find those fish. The same is with SETI, they have not checked out enough of the universe to conclude if there is someone out there.
“If we ever hope to pick up the signal from out there, we need to build a radio telescope the size of the metropolitan area of Chicago, which is twenty-five thousand eight hundred square kilometers. Then it would be possible to detect a radio signal hundreds of light-years away. The only problem is such a telescope in our economy would cost more than 60 trillion dollars,” says Keith Cooper, a famous science journalist, in his book ‘The Contact Paradox’.
Moreover, communication is only achievable when we assume that out there civilization is as advanced as ours is. However, the Copernican Principle that asserts that we are not special in any way, suggests that the odds are far too slim that another planet is at precisely the same point in its development. The calculations hint that the signal would have to traverse a distance of more than ten million light years for more than two millennia before we receive a response. Hence, we will not get a response even at light speed, before the year 4000 C.E.
This implies that the universe is extremely vast. It would take centuries for establishing the first contact, as far as the math is concerned.
Rare earth hypothesis
The Rare Earth Hypothesis deals with the notion that planets like Earth are scarce. Life and the evolution of complexity requires a combination of astrophysical and geological conditions that are not common in our Universe. In other words, we are quite special and unique. Thus, a complex ET life is an improbable phenomenon which is likely to be rare throughout the universe.
In 2000, Peter D. Ward and Donald published a book titled “Rare Earth: Why Complex Uncommon in the Universe”. In their book, the authors indicated eighteen factors that allow complex life to evolve until they obtain intelligence. Most of them are very unlikely and their relative independence implies that their probabilities must factorize, making the resulting probability for intelligence to evolve elsewhere than Earth really very, very low.
Dark forest theory
This possible answer to the Fermi paradox says that, the aliens out there are silent simply because they do not wish to be on the receiving end of possible destruction by another civilization. Just like hunters moving cautiously through a dark forest, they all must remain quiet otherwise; they will be found and killed.
This would also explain why we have not found any mundane alien radio signals despite a century of being able to pick them up. Just as we accidentally send our radio signals, meant for us, out into space, another civilization would be likely to as well. One possibility is that other civilizations are so frightened of being detected that they deliberately avoid sending any such evidence out into space.
Nonetheless, the possibility of an alien civilization that has a similar risk aversion level and reasoning process as we do must be taken into account.
With billions of years of history at play, it might not be the case where we are on technological parity with all the other forms of life that might be out there. Alien life might simply be so far beyond us that they could regard us as insignificant as we do when we think of an ant. Why do you not try to talk to the insects in your garden? The gap is too great. They might not be talking to us because they think we have nothing interesting to say. You understand what they want perfectly, and they have no hope of understanding you so the communication is frankly, pointless.
When I infer in the light of these arguments, is finding a substantial probability that we are alone in our galaxy, or even in our observable universe.
Where are they? — Probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable. But as of now, we are simply not listening to them the right way. Perhaps, in the near future, if we follow a more practical approach, which can provide certainty about intelligent life somewhere other than Earth. However, to be honest, for now it looks more as if the aliens are just inanimate characters of science fiction movies.
- Musso, P. (2001, August). On the last terms of Drake Equation: the problem of energy sources and the” Rare Earth Hypothesis”. In Exo-/Astro-Biology (Vol. 496, pp. 379-382).
- “The Fermi Paradox Revisited” article in Smithsonian magazine.
- Hart, M. H. (1995). An Explanation for the Absence of Extraterrestrials. Extraterrestrials: Where Are They?
- “The Contact Paradox: Challenging Our Assumptions in the Search for Extraterrestrial Intelligence” book by Keith Cooper
- Webb, S. (2015) “If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY?” Science and Fiction. Springer, Cham. https://doi.org/10.1007/978-3-319-13236-5_6
Aly Muhammad Gajani holds a Master’s degree in Space Science and Technology specializing in Astrophysics together with GIS applications. His research focus is in the fields of galaxy evolution, astrophysical cosmology, exoplanet detection, and computational astronomy.