The Great Filter is the idea that there is some single, almost insurmountably improbable barrier on the path to the stars that explains why we've never seen any sign of alien life. It combines aspects of astronomy, biology and history to arrive at one inescapable conclusion: university professors dream of book deals.
Robin Hanson of George Mason University posits a "Great Filter" that prevents the rise of intelligent, self-aware, technologically advanced, space-colonizing civilizations. The "filter" would be one or more improbable steps along the path that starts with the creation of a planet and ends with a race capable of colonizing the galaxy.
Somewhere between those two points, philosopher Nick Bostrom points out, "the Great Filter operates, and it must be powerful enough that even with all the billions of possible starting worlds on which life might evolve - all those rolls of the cosmic dice - one ends up with nothing: no aliens, no spacecraft, no signals, at least not in our neck of the woods."
The very existence of life makes finding a four-leafed clover with winning lottery tickets for leaves look like a sure thing. Add the staggering improbability of our evolution from single cells and you end up with odds so vast they've driven the invention of everything from the Drake equation to an invisible sky-beard who seems unnecessarily preoccupied with what we do one day out of every seven. People who study this subject file all that under "Shit we already knew", and were too busy actually working on the science to come up with a garbage buzzword phrase that would look really awesome in bold type on the cover of a hardback book (available now for $29.99!) Luckily Robin Hanson was ready to do that for them.
There isn't actually a book yet, but the Great Filter "theory" is so clearly designed to be publisher-ready you can almost see the page numbering. It talks in grand terms about a vast threat facing humanity, and if it never seems to have any idea what that threat actually is, was or will be then who cares? Most of the 'evidence' is based on the scarcity of life in the cosmos in general and how that describes threats to Earth specifically, otherwise known as "Fundamental misunderstanding of statistics #1". He goes on to talk around this ethereal menace and all the effects it could have on THE SURVIVAL OF EARTH, combining lots of different fields in compelling pop-science friendly chapters without ever coming up with an actual result.
Not that we're claiming that Professor Hanson doesn't understand all this; just that he's made a tactical decision not to care. His real intentions are further revealed by the way he throws around "possibility of world-destroying physics experiments" (we're assuming he'll scribble "I'M TALKING ABOUT THE LARGE HADRON COLLIDER" on autographed copies). This is a great buzzword for catching media attention and popular sales, at the tiny price of sacrificing even the pretense of scientific validity. Everyone who's even heard of the basic physics of the LHC knows these cataclysm quotes are garbage.
Bostrom, director of the awesomely titled Future of Humanity Institute at Oxford University, claims that the Great Filter poses an "Existential Risk". That's a perfect choice of words because he thinks it means a threat to our very existence, when it's really a made-up Nietzschean problem for people who should be delighted but are determined to be miserable anyway. He confirms this assessment by telling us we should take any discovery of alien life as terrible news, as that would put this mysteriously unspecified Filtering Boogeyman in our future instead of the past.
Listen: if we discover life on Mars and you can honestly call that a bad thing, then it's not just that you aren't a scientist. We're not even sure you could be described as human.
Posted by Luke McKinney.
Related Galaxy posts:
The METI Controversy: Is Detection by Alien Life a Threat to the Human Species?
Babelfish -Universal Translator Will Allow ET to Speak English
The 1.5 Gigayear Technology Gap
Advanced Civilizations in the Universe -A Galaxy Insight
"The Great Silence" -A Galaxy Insight
NASA's "New Worlds Observer" Will be Able to Spot Oceans, Continents and Clouds on Small Rocky Planets
MIT Asks: How Would Extraterrestrial Astronomers Study Earth?
Harvard-Smithsonian Scientists Zero In On Key Sign of Habitable Worlds
Cruising the Goldilocks Zone -The Search for Super Earths
Dead Zones in the Search for Extraterrestrial Life