Great ideas are born out of the blue. Out of all random and unexpected thoughts, one changed the way we perceive the metaphysics of the world, the notion of cosmos, and human existence, forever. It was the year 1950, when Enrico Fermi — creator of the nuclear reactor a.k.a pretty smart guy — while having lunch with colleagues of his, shouted, exuberantly enough,
“Where are they?”.
[1] By ‘they’, he meant extra-terrestrials, intelligent beings from outer space, or interstellar-colonizers; whatever you — the reader — may call them. The 1950s were decent times for such a question to be asked, weren’t they? “The true Golden Age” of science fiction, as it was coined by Robert Silverberg.
[2] Looking at the fellas who worked throughout the middle of the last century, with Bradbury, Asimov, and Clarke on top of the list, the time for the scientific exploration, or scientific questioning, at least, seems to be about right. So indeed, where are they? If they are somewhere out there, why don’t they come to Earth?
The Question (I’m allowing myself to capitalize the word) leads to the unexplained — the paradox in itself — which is still discussed; today more than ever, maybe. To understand the paradox of it, I shall jump into the concrete scientific basis first, yet, later, shall proceed with the explanation suitable for all the audiences out there. The paradox arises from the conflict between the high scale and probability of existence of the external life, with Fact A,
[3] claiming that there are no intelligent extra-terrestrials on Earth at the moment.
[4] Even though, many years had passed since ‘the moment’, i.e. the time of the publication of the paper, or 1974, we still haven’t encountered any life in the outer space. Counter-intuitive, isn’t it? For a scientist, at least, it should be.
When we look at the starry sky, what we observe is roughly two-thousand-five-hundred stars, or one percent of the diameter of the Milky Way — the galaxy of our own — in which there are,
at least, one hundred billion stars.
[5] Weirdly enough, this equals to the number of galaxies in the observable universe; who knows how many more are out there unobserved? Math is useful here: all in all,
there are between 10^22 and 10^24 stars in the observable universe. On average, scientists agree, roughly tenth of all the stars are like the star of our own — the Sun — thus similar in size, temperature, and luminosity.
[6] These are the requirements for the Earth-like planet to originate
in the Goldilocks Zone, where the planet is neither too hot nor too cold for the liquid water to exist.
[7] Assuming that only half of the scientific predictions are true (five percent), there are five-hundred quintillion Sun-like stars, out of which roughly twenty-two percent can sustain liquid water.
This equals an enormous 100 quintillion potential Earth-like planets. [
8] If we speculate a bit and say that one percent of all Earth-like planets developed life, out of which one percent advanced it to the intelligent level comparable to that we have achieved on Earth,
there should be ten quadrillion intelligent civilisations in the observable universe, out of which hundred thousand happen to be in the Milky Way.
[9] Yet, not a single one of them had reached the Earth, ever.
If you thought that the evolutionary scale is big enough, you were right; yet the cosmological scale is even bigger. The Milky Way — one of the pioneer galaxies after the Big Bang — originated roughly thirteen billion years ago.
[10] Obviously, in the beginning, for about two billion years, every component was too-of-something: too hot, too dense, too explosive. Yet
some time around ten billion years ago, first habitable planets were born.
[11] The Earth is only four billion years old, thus leaving space for the speculation enabling loads of planets within the habitable zone to develop life. It is speculation, because we are not aware of any life, apart from our own. If at least one of these vast amounts of chances had been fulfilled, which is, developed into cosmos-exploring civilization, we would have experienced the extra-terrestrial life; yet, we haven’t. Nevertheless, we can still predict how these intelligent civilizations could be grouped — this is what the Kardashev Scale is used for.
[12]The interstellar space-travel, as bizarre as it sounds, is still theoretically possible. It has two dimensions: time and energy. Assuming a spaceship is voyaging through the cosmos at the speed of light, it would still require hundreds of years until it arrives at any of the habitable planets. Yet, the civilization that started to develop, let’s say a billion years earlier than Earth, along with the lines of same evolutionary path, could be said to be a billion years ahead of us — humans — in terms of technological advancement. Probably, they would have tried to extend the lifespan of themselves — whatever creatures they are — through the advancement of medicine, or at least the notion, which we, on Earth, call medicine. Thus, for them, a couple of hundred years may be the tiny part of the lifespan, enabling them to voyage through the cosmos. Let us jump into the tricky bit of the interstellar space-travel dimension — energy. Since the examples are theoretical, the tool — the Kardashev Scale — is also theoretical and, some will say, speculative. Yet, it is useful, since it puts the energy consumption of an entire civilization into a cosmic perspective, consequently enabling to measure technological advancement.
[13] Here, I would rely on the laconic summary by Huffington Post
[14]:
A Type I Civilization has the ability to use all of the energy on their planet. We’re not quite a Type I Civilization, but we’re close (Carl Sagan created a formula for this scale which puts us at a Type 0.7 Civilization).
A Type II Civilization can harness all of the energy of their host star. Our feeble Type I brains can hardly imagine how someone would do this, but we’ve tried our best, imagining things like a Dyson Sphere.
A Type III Civilization blows the other two away, accessing power comparable to that of the entire Milky Way galaxy.
Remembering that the development of intelligent life on a given hypothetical planet started billions of years before it started on Earth, the assumption that the civilization achieved the Type III Civilization status, seems reasonable, thus, once again, allowing for the interstellar space-travel to exist, at least theoretically.
[15] Yet, if intelligent civilizations exist and can travel in space, why can’t we interact with them? There are several explanations out there, which can be gathered into two major groups, based on the distinction of whether Type II and Type III Civilizations exist, or not.
[16] I shall discuss both below.
The First Explanation Group is all about math and scale and probability principle discussed at the beginning. According to the initial claim, the higher civilizations have not contacted us, simply, because they do not exist.
Yet, the math proves the potential existence of millions of intelligent civilizations, meaning that there should be some external factor preventing them from contacting us. [17] In the scientific world, this is called the Great Filter.
[18] Kurzgesagt defines it as “a challenge or danger so hard to overcome, that it eliminates almost every species that encounters it”.
[19] If you want food for thought, maybe, global warming is a good example. Assuming that the Great Filter exists, we are left with three alternatives, depending on when the filter is in the time-structure.
[20] The
first alternative claims that the Great Filter is behind us, thus us, and civilizations like us, are very, very rare.
Second alternative claims that the Great Filter is way ahead of us, meaning that we, alongside many more civilizations, are still on the route to the higher intelligence since we were one of the earliest civilizations out there.
Third alternative claims that the end is near, being it a natural catastrophe like gamma-ray bursts, or nuclear war. The near-in-the-future exploration of Mars can shed light on where are we, and where is the Great Filter. Nick Bostrom of Oxford University claimed he would be happy if the probes from Mars would indicate the complete sterility since otherwise,
the more developed life is found there, the closer will we find ourselves to the Great Filter — the inevitable elimination of our civilization.
[21]The Second Explanation Group shares the ideas of the Mediocrity Principle — something contrary to the notion we had during the Renaissance — according to which there is nothing rare about our galaxy, and that there are many more intelligent civilizations in cosmos, yet we have not heard of them, because of some underlying logical reasons.
[22] Here, to illustrate a few of the possibilities, I would rely on the paraphrase of some portions of the laconic summary by Wait But Why:
[23]Possibility 1: Super-intelligent life could very well have already visited Earth, but before we were here. The sentient history of humankind is only fifty-thousand years old, while the recorded history constitutes only tenth of it. Maybe intelligent extra-terrestrial civilizations visited us, when, we were not ready to express it.
Possibility 2: The entire concept of physical colonization is a hilariously backward concept to a more advanced species. With the Dyson Sphere constructed around the star providing unlimited resources, a civilization may not even consider voyaging for the cold interstellar space travel.
Possibility 3: There’s plenty of activity and noise out there, but our technology is too primitive and we’re listening for the wrong things. There are no reasonable grounds to believe that if intelligent extraterrestrial civilizations exist, they are like us in any way. The channels of communications may be so different from anything existing on Earth, that our technology is not enough to capture their signal.
Possibility 4: Higher civilizations are here, all around us. But we’re too primitive to perceive them. Michio Kaku compares us to the ants living in the anthill, next to which the highway is built by humans, creatures more intelligent to ants. Will we, like ants, be able to understand what is going on? No, since ants are too primitive compared to humans. The metaphor is applicable to any civilization located higher on the intelligence scale.
There is something in human nature, that makes us curious about everything we encounter. At first philosophy, but later — science — had always been the object of intellectual inquiry. Curiosity enabled Enrico Fermi to ask himself the famous question, and others to fill the vacuum that had been created. No matter what we discover in the future — whether we are the only intelligent creatures, whether there are many more like us, whether we will extinguish ourselves through means of nuclear war or any other Great Filter, whether we will cohabitate with other intelligent creatures somewhere in the Empire of a Thousand Planets,
[24] the result will be the ultimate revelation of human curiosity. For now, we must wait. Wait and constantly ask ourselves: “Where are they?”.
* * *
[1] Some accounts indicate that the actual phrase was “Where is everybody?” From Jones, Eric M. 1985. “Where is Everybody? An Account of Fermi’s Question.” (Los Alamos National Laboratory).
[3] Hart, Michael H. 1974. “An Explanation for the Absense of Extraterrestrials on Earth.” Quarterly Journal of the Royal Astronomical Society 16: 128–135.
[4] Here, I am adopting Michael H. Hart’s notation, please refer to the footnote 3.
[5] Here, I am relying on the calculations by Urban, Tim. 2014. “The Fermi Paradox.” Huffington Post, June 17.
[6] Plait, Phil. 2013. “The Sky May Be Filled with Earth-like Planets.” Slate, November 4.
[7] Plait, Phil. 2013. “The Sky May Be Filled with Earth-like Planets.” Slate, November 4.
[8] Petigura, Erik A., Andrew W. Howard, and Geoffrey W. Marcy. 2013. “Prevalence of Earth-size planets orbiting Sun-like stars.” Proceedings of the National Academy of Sciences of the United States of America.
[9] Urban, Tim. 2014. “The Fermi Paradox.” Huffington Post, June 17.
[10] ESO. 2004. “How Old is the Milky Way ?” European Southern Observatory, August 17
[11] 2015. The Fermi Paradox — Where Are All The Aliens? (1/2). YouTube. Performed by In a Nutshell Kurzgesagt.
[12] 2015. The Fermi Paradox — Where Are All The Aliens? (1/2). YouTube. Performed by In a Nutshell Kurzgesagt.
[13] Creighton, Jolene. 2014. “The Kardashev Scale — Type I, II, III, IV & V Civilization.” Futurism/The Byte, July 19.
[14] Urban, Tim. 2014. “The Fermi Paradox.” Huffington Post, June 17.
[15] 2015. The Fermi Paradox — Where Are All The Aliens? (1/2). YouTube. Performed by In a Nutshell Kurzgesagt.
[16
] Urban, Tim. 2014. “The Fermi Paradox.” Wait But Why, May 21.
[17] Urban, Tim. 2014. “The Fermi Paradox.” Wait But Why, May 21.
[18] 2015. The Fermi Paradox — Where Are All The Aliens? (1/2). YouTube. Performed by In a Nutshell Kurzgesagt.
[19] 2018. Why Alien Life Would be our Doom — The Great Filter. YouTube. Performed by In a Nutshell Kurzegasagt.
[20] Urban, Tim. 2014. “The Fermi Paradox.” Wait But Why, May 21.
[21] Bostrom, Nick. 2008. “Where Are They? Why I Hope the Searcg for Extraterrestrial Life Finds Nothing.” MIT Technology Review (May/June): 72–77.
[22] Urban, Tim. 2014. “The Fermi Paradox.” Wait But Why, May 21.
[23] Urban, Tim. 2014. “The Fermi Paradox.” Wait But Why, May 21.
[24] Mézières, Jean-Claude, and Pierre Christin. 2011. Valerian & Laureline — The Empire of a Thousand Planets. Canterbury, Kent: Cinebook.