We are all alone. Or are we? There is no definitive proof of alien life — at least any widely accepted proof — despite the vast number of planets that have orbited the stars of the Milky Way for billions of years. This is the quandary that the mathematician Enrico Fermi pondered in 1961.
After all, this universe is billions of years old with billions of planets orbiting billions of stars. Even the slowest ships and least habitable planets should have led to galactic empires. This thought experiment is known as the Fermi Paradox. Where is everyone if it makes mathematical sense for the universe to be teeming with intelligence? Plenty of answers have emerged but two stand out.
Even the slowest ships and least habitable planets should have led to galactic empires. This thought experiment is known as the Fermi Paradox.
First and most likely, the Great Filter theory stands like this: Imagine a filter that prevents life on planets from progressing. To move on would earmark the planet as the cradle of a galactic empire, but to stop would leave it a dead world. For example, perhaps the Great Filter is eukaryotic life. Maybe it’s easy for prokaryotes to emerge, but the sweeping majority of planets cannot progress to eukaryotic and therefore multicellular life.
The universe has life, but the Great Filter leaves it dumb. But what if Earth still lies behind the filter, waiting for its trial? It is all too possible as humans are still relatively weak and quiet. Human-like civilizations could easily prosper without us knowing. In this scenario, it is not thoughtless organisms who need to pass the filter but emerging empires. Is nuclear war an intergalactic issue? Do all civilizations misuse antibiotics, giving rise to horrible superbugs that wipe out entire planets? Whatever it is, a hypothetical, coming filter would have to be so incredibly destructive that no civilization in 10 billion years has crossed it.
The universe has life, but the Great Filter leaves it dumb. But what if Earth still lies behind the filter, waiting for its trial? It is all too possible as humans are still relatively weak and quiet.
There is a second creepier answer. At least in the case of the Great Filter, these races are responsible for their own destruction. In the Dark Forest Theory, the galactic radio silence has been produced by annihilation and fear. What if all noisy civilizations have been destroyed by an ancient, primordial civilization? What if all the life out there has learned to be silent? What if the universe is ruled by a galactic punisher, ready to hit anything that makes a sound? What if sending out signals was a mistake?
Image courtesy of Arizona Public Media
