On The “Great Filter” of Civilizations

Back in the 1960s, Frank Drake wrote a probability equation to estimate the number of extraterrestrial civilizations that ought to exist in the Milky Way. More specifically, it quantified the number of civilizations capable of manipulating electromagnetism, which we’d be able to detect. Here it is below, courtesy Wikipedia:

It’s pretty simple. Too simple, in fact.

Though the Drake Equation wasn’t comprehensive (it was meant to ‘stimulate dialogue’ in the scientific community about alien life) and was by no means a precise estimate, the number of alien civilizations that could be detected by us is massive. Even if you take the most pessimistic number of intelligent civilizations outside our solar system, the resulting number is in the thousands — we should be swamped in radio emissions from alien television shows, alien satellite transmissions, and whatnot.

But we see no evidence of this. Sure, there’s the WOW Signal. But to date, there has been no definitive evidence of intelligent alien life outside our solar system.

And herein lies the Fermi Paradox — if the probability of intelligent life elsewhere is so high, why haven’t we seen any evidence for it?

The Great Filter, like Adam Smith’s Invisible Hand, is a terminology used to describe the inevitable side-effect of a phenomenon. The Great Filter is not something one can touch, smell, or even see, for that matter — it’s an explanation for why we can’t detect evidence of other intelligent civilizations.

ONE of those hypotheses is the Great Filter. The Great Filter posits that EVERY civilization that attains a certain level of development somehow destroys itself. As an example, the human race got extremely close to destroying itself at the beginning of the Cold War due to the manufacturing of apocalypse-heralding nuclear warheads. The Doomsday Clock was created as a measure for how close we are as a civilization to destroying ourselves.

Von Neumann, the visionary physicist, even hypothesized self-replicating alien spacecraft called Berserkers that lie dormant in solar systems until awaking to exterminate all detected intelligent life in that system.

Like a filtration device, the Great Filter ‘filters’ out all civilizations from crossing some arbitrary point in their development, such as the creation of the nuclear bombs. The technology we develop ends up destroying us. All civilizations end up destroying themselves.

Of course, the great filter is only a hypothetical explanation for the Fermi Paradox. One could disprove it by discovering an intelligent extraterrestrial civilization, but other than that, there’s really no way to prove it.

The Great Filter, like the Invisible Hand, could be the subject of much debate over the next few decades.