On Tuesday (May 10), NASA’s Kepler mission announced that it had nearly doubled the number of exoplanets we’ve discovered. Based on this data, NASA scientists expect there are tens of billions of Earth-like planets just in our own galaxy. That, however, might be really bad news for humanity.
Ever since humans grasped the reality that we live on a tiny planet in a vast universe, we’ve wondered whether there is intelligent life elsewhere. A simple equation, called the Drake equation, is the best way we have to estimate how many intelligent civilizations exist in a galaxy.
When the equation was developed, one of the factors in it was how many planets existed around other stars. Because we didn’t have any direct proof of the existence of exoplanets, astronomers made conservative estimates. However, NASA’s discovery now shows that there may be tens of billions of Earth-like planets in just the Milky Way. When the new number is inserted into the Drake equation, it estimates that there must between tens of thousands to millions of intelligent civilizations in our galaxy.
And, yet, in decades of searching for aliens, we’ve never found any signs. No radio signals. No odd objects arounds stars. No fly-bys of spaceships. Nada. This apparent contradiction is the Fermi Paradox: “Where is everyone?”
There are as many ways of answering the Fermi Paradox as there are ways to eat a bagel. Each scientist in the field has his or her own favorite explanation. But one, the theory of the Great Filter, explained by Andrew-Snyder Beattie of Oxford University, sets out the worrying possibility of near-term human extinction.
It goes like this: Each life form has to go through a series of steps to become a space-faring civilization and live happily ever after. First, single-celled organisms have to become multi-cellular. Then multi-cellular organisms need to become intelligent. Next, intelligent organisms have to build an organized society so that they can pool their efforts. Finally, to continue living, they have to leave their original solar system and find a new one, because at some point the original star will run out of fuel and explode.
Beattie argues that one of these steps is the “Great Filter,” which means that each life form, no matter how hardy, fails at some point, and thus does not become a space-faring civilization. Given that humans have crossed all but one of those steps, the Great Filter must be the final step.
Put another way, if the Drake equation is right, then there are, at this very moment, many millions of intelligent civilizations in our galaxy, including some more advanced than us. Some of these would have thought of developing interstellar travel and put the time and effort into developing it.
However, if any of these civilizations had developed interstellar travel, within a few million years they would have been capable of building a vast civilization. Since none have visited us or shown any evidence of their existence, it must be that none of them were able to develop interstellar travel. Each of these intelligent civilizations, the theory goes, was consumed by the catastrophic Great Filter before it could leave its solar system. Likewise, we await the Great Filter, which will crush our hopes of becoming a space-faring civilization and spell our ultimate doom.
And, yet, it might not be so bad. There are more hopeful explanations for the Fermi Paradox—such as that intelligent civilizations are just too far apart to ever know of each other’s existence. If there’s one thing humanity has evolved to do well, it is to hope.