"We may yet find ourselves detecting the shrieks of civilizations across our galaxy."

Distress Signal

If there are any intelligent alien societies out there, we may never be able to spot them until things go horribly wrong on their home world.

It's one possible reason for why the search for extraterrestrial life hasn't turned up anything, Caleb Scharf, the head of astrobiology at Columbia University, wrote in a Scientific American op-ed. When things are going smoothly at home, alien civilizations may not be putting any technosignatures out into the cosmos. But when facing the apocalypse, Scharf argues, there may be more visible signs for us to pick up on.

Race Against Time

One of the main ways that scientists hunt for extraterrestrials is to look for signs of technology, like radio signals or unusual structures. But the most visible signs might be attempts to geoengineer their home world or terraform another, or even a distress signal, if they're on the brink of extinction.

As Scharf wrote, "it's possible that sentient, technological species experiencing change and trauma might be the ones most likely to give away their presence to the rest of the galaxy."

Last Gasp

It's also possible that theoretical civilizations die off without "even a whimper," Scharf wrote — unless we happen to spot signals like an atmosphere changed by pollution. But compared to the size of the cosmos, our search for alien life has been minuscule.

"We may yet find ourselves detecting the shrieks of civilizations across our galaxy," Scharf wrote.

READ MORE: It's the End of the World ... Somewhere [Scientific American]

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