|What’s new? Proposed solutions to Fermi’s Paradox fit into three broad categories.
- One: They’re nowhere—and no-when. Aliens don’t exist, and they never have.Today, cosmologists estimate that there are as many as 500 billion billion sunlike stars, with 100 billion billion Earthlike planets. The more we learn about the universe, the more absurd it would seem if all but one of those bodies were bereft of life.
- Two: Life is out there—but intelligence isn’t. Where present, life may be something more like microbes or algae, not underwater cities. it’s notable that Earth has several million species of life, but only one has produced a civilisation—that we know of. The relative silence of the universe suggests some kind of “Great Filter” that is restricting the creation of more intelligent beings.
- Three: Intelligent life is abundant—but quiet. Maybe humanity is still so basic and primitive that advanced civilisations don’t think we’re worth talking to. Or maybe those other civilisations have learned that broadcasting their existence leads to extermination at the hands of violent, intergalactic colonisers. Or maybe …