Fermi’s Paradox and the Great Filter


Photo: https://astrobites.org/2016/03/15/classifying-civilisations-an-introduction-to-the-kardashev-scale/

Cartoon showing the different Kardashev types. Each rung on the ladder uses larger astrophysical objects as its energy source, from single planets to whole clusters of galaxies. Source: Cirkovic 2015, Kardashev’s Classification at 50+: A Fine Vehicle with Room for Improvement

Fermi’s Paradox is the connection between the probability in the stars of the occurrence of extraterrestrial life and the sheer lack of evidence thereof.

Assuming the Mediocrity principle, in which Terra (Earth) is a typical planet, there are around 70 sextillion stars in the observable universe, and 200-400 billion stars in the milky way with planets in their habitable region, meaning there should be an immense number of existing intelligent civilizations or species outside of our under the assumption extraterrestrial life follows the same survival principals as our own, and that’s not taking into consideration the many habitats other species could possibly evolve or live within. In the 13.8 Billion years this universe has existed, we have found no such evidence of these civilizations, so where are they? This poses a question we’ve yet to answer, but many have come up with possible explanations as to why. The first person to ask this question, and later address it was Enrico Fermi. He was an Italian naturalized-American, Born September 29, 1901 and referred to popularly as ‘the Architect of the Nuclear Age”. Fermi was a physicist, The first to create a nuclear power reactor, and the 1938 Nobel Prize prize winner in physics.

There are two ways, or two questions that can be asked in reference to Fermi’s Paradox. The first being “Why have we found no proof of alien artifacts or civilization anywhere here on earth or anywhere else in the solar system?” If we were to fund interstellar travel, even at our current technological rate which, to a class 3 society is quite slow and primitive in relation to the Kardashev scale, we would find it would take nearly 5-50 million years to colonize the galaxy, or in other words our local cluster. To humans this seems like a long time, but in comparison to a cosmological scale it’s a fairly short period. After this has been realized, a new question forms. “Why has the galaxy not been colonized already, either by us or other sentient beings with the probability to exist?”

This can lead to the second question that can be asked. “Why have we found no signs of extraterrestrial intelligence anywhere in the universe?” This question does not assume interstellar travel, but does include other galaxies. In this line of thinking, it is entirely possible that these civilizations exist outside our scope of reach in our local cluster, but the scale argument points out that despite these civilizations being out of our reach, we may not be out of theirs. The question still begs, “Why, if the probability exists, can we not find the signs?”

One explanation for the lack of Alien species and scientific discovery is the Great Filter. The great filter, at its core, is the argument that for one or more reasons the probability argument with respect to extraterrestrial life is flawed. They say this in regards to Fermi’s Paradox that one or more steps in the chain of evolution to reaching a class 3 society, accomplishing interstellar travel and colonizing the galaxy must be improbable, or impossible. This can be for many, or any reason. There is an immense number of contingencies that can interfere with reaching the goal of exploratory space measures, and there are a few ways to look at the Great Filter. Some of the most prominent include anything from nuclear war, to disease or an unlucky asteroid wiping out a potential sentient species.

Furthermore, this brings -the question upon our species. Have we passed the great filter? Or is it ahead of us? A scarier line of thought is to ask; Is there more than one great filter? If so, how many have we survived unknowingly? For instance, any pandemic the human race has ever endured. The Black Plague was an epidemic in which Europe lost 30-50% of its population. In the ice age, humanity’s entire population decreased to less than 10 Million people world wide. We’ve survived multiple possible great filters, but the most important question remains.

Could we survive another one?