illustration by paul sahre
If the universe is unimaginably large, why aren’t there more signs of extraterrestrial life?
The question was made famous by Enrico Fermi, who at lunch one day in 1950 turned to his colleagues and asked, where are they?
With billions of stars in our stellar neighborhood, there’s a high probability some of the planets surrounding at least some of those stars must be Earth-like. Chances are, at least a portion of those life-fostering planets must have developed civilizations with the capability to leave their planet, just as we have.
Since there exists many stars similar to our Sun, but that are billions of years older, the theory holds that humans should have been able to detect some sign of an alien civilization.
But we never have—at least, not convincingly.
The strongest argument against the Fermi Paradox, at least according to Avi Loeb, author of the book Extraterrestrials, unfolded over 11 days in 2017. That October, a telescope in Maui captured an exotic spec careening across the sky. They called it ‘Oumuamua (which translates roughly to the Hawaiian for “scout”). Scientists assumed it was a comet or asteroid. Loeb disagrees.
The former chair of Astrophysics at Harvard, Loeb has reason to believe ‘Oumuamua was an alien craft propelled by a lightsail — a thin reflective object that harnesses light to push a vehicle across space in the way a sailboat is pushed by the wind.
What evidence does Loeb have? Three compelling facts.
First, ‘Oumuamua was not shaped like a normal comet or asteroid. It looked something like a pancake the size of a football field.
Second, its trail was minimal. For a comet going four times faster than average, scientists expected there to be a large tail of debris behind ‘Oumuamua — but no carbon-based molecules or space dust were detected.
Lastly, ‘Oumuamua was moving away from the sun much faster than gravity’s pull would provide. What provided the extra push?
david steinberg
Planetary sailing
In 2015, Loeb worked on a project to bring a tiny probe to Alpha Centauri, a star system about four lightyears from our Sun. He and a team of researchers worked through several possible designs, and eventually landed on the lightsail — a craft propelled by a strong laser light. That laser could ignite in short, powerful bursts, which would propel the craft up to 100 million miles an hour — a fifth the speed of light. Moving at that speed, it would take only about nine days to reach Pluto from Earth.
Loeb believes ‘Oumuamua may have been a craft using similar technology.
“Extraordinary claims require extraordinary evidence.”
Whether he is correct or speculative remains to be seen. It’s certainly beyond my pay grade. By Sagan’s standard, ‘Oumuamua sadly falls short. But it does give one hope.
It’s only recently that we’ve developed the technology to have telescopes as powerful as the Pan-Starrs1, which originally detected ‘Oumuamua. The object was passing at a distance from us roughly equal to our distance from the Sun. Now that we have this level of tech, Loeb expects sightings of unusual objects to become more commonplace.
Perhaps the reason we haven’t seen any alien life up until now is because we didn’t yet have the technology to detect it.