On Tuesday, physicist Stephen Hawking and billionaire Yuri Milner announced an ambitious plan to send thousands of tiny robots to Alpha Centauri, a star that's 4.37 light-years away.
The $100 million project — Breakthrough Starshot — is undeniably ambitious but seemingly not out of reach.
And that got two Starshot team members thinking: If we can do it, why not aliens? What if they've already visited our own solar system with tiny robots? Would we have noticed?
Harvard astrophysicist Avi Loeb and Ann Druyan — an author, TV producer, and longtime collaborator/spouse of Carl Sagan — brought up the radical if not creepy idea during Monday's big announcement of Starshot.
"You must wonder if there's a possibility that such things are flying near us from other civilizations," Loeb speculated. "They're moving so fast and so small, they don't transmit much energy — that we won't notice."
"Is that a solution to the Fermi paradox?" Druyan asked.
"It's one possibility," Loeb replied.
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The Fermi paradox is a puzzle that has long-baffled astrophysicists and amateur alien hunters. It basically boils down to this question: Where is everybody?
It's a good inquiry. The universe is incomprehensibly huge and contains a near-infinite number of possibilities for life, on this planet and elsewhere.
What's more, logic suggests not only that extraterrestrials are out there, but also that some of them are more advanced then we are. So why has no one come knocking? No would-be colonizers, no Vulcans, not even a friendly galactic neighbor to borrow a cup of sugar?
We don't know. It doesn't make any sense. That's why it's a paradox.
If aliens did visit us with iPhone-size robots, as Starshot proposes to do, it's likely we haven't — and maybe even couldn't have — noticed yet. After all, we have enough trouble detecting asteroids that could wipe out a city.
In any case, Druyan doesn't seem too concerned about robotic alien flybys.
"I feel very strongly that those extraterrestrials are beautiful until proven ugly," she said, "because of the great feat and demonstration of maturity that's required to learn how to be a space-faring civilization."
This explanation isn't the only solution to the Fermi paradox. And, frankly, it's perhaps the least-unsettling option.
