Where are the extraterrestrials?

Posted by Alison Klesman
on Friday, October 20, 2017

Physicist Enrico Fermi asked why, if extraterrestrial intelligence is ubiquitous, other civilizations have never visited us.

By Richard Talcott

While discussing the possibility of intelligent life in the universe over lunch with his fellow scientists, Nobel Prize-winning physicist Enrico Fermi asked the simple question: “Where are they?” The line came to be known as the “Fermi Paradox,” and the argument boils down to this: If the universe is teeming with life, and some reasonable percentage of that life has developed advanced technology, then these civilizations should have populated our corner of the Milky Way long ago. Several potential solutions to the paradox exist, ranging from the possibility that we’re alone in the cosmos to the chance that the aliens already live among us.

Thursday at the 49th annual meeting of the Division for Planetary Sciences in Provo, Utah, S. Alan Stern suggested a new solution: Perhaps the aliens populate ocean worlds cut off from the outside universe by thick crusts of ice or rock. Stern, best known as the principal investigator on the New Horizons mission that explored Pluto, points out that we now know of at least four such worlds in our solar system, and evidence suggests there could be five or more additional ones. And there’s no reason to suspect that they wouldn’t be common among the exoplanet population.

Such water worlds might even have a few advantages over their surface-water cousins. For one, they would be better protected from external hazards like harsh radiation, large impacts, and changing climates. Interior oceans would provide a more stable environment that poses less risk to any life that might develop. But their thick crusts also naturally isolate them from the universe beyond. They would be hard to detect and would face enormous difficulties communicating with the outside world — if they even knew a greater world existed.

The existence of these ocean environments hidden beneath thick shells could offer an elegant solution to the Fermi Paradox, and fittingly one that Enrico and his lunch buddies could never have imagined.

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