Where are all the aliens? Probably dead, a new study claims
In a universe that’s so massive and teeming with potentially habitable planets, why are our galactic neighbours so quiet? It’s a paradox that has troubled plenty of minds over the years, but one possible solution mooted in a new study is a touch on the depressing side: the dead just aren’t that loud.
A studyfrom The Australian National University suggests that life on other planets would typically die out extremely quickly – either by runaway heating or cooling. In fact, the researchers argue, our ridiculously hot neighbour Venus and the ridiculously cold Mars were once perfectly habitable… four billion years ago. Early life on either would have been wiped out as the planet’s environment changed in the billion years that followed.
So what makes Earth special, according to this theory? Turns out it’s us. You and me, kid: we did it. Or rather, our evolutionary ancestors did. “Life on Earth probably played a leading role in stabilising the planet’s climate,” professor Charley Lineweaver from the ANU Planetary Science Institute told Phys.org.
If that’s the case, that makes our planet pretty damned rare. That’s the luck of the evolutionary draw for you. As Dr Aditya Chopra from ANU explains: “Early life is fragile, so we believe it rarely evolves quickly enough to survive. Most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable.” That’s exactly what happened on Earth.
Of course, this is also a neat answer to the Fermi Paradox – why we haven’t heard from aliens. They’re all dead, losing the evolutionary lottery and dying out as their planets rapidly changed.
“The mystery of why we haven’t yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces,” explains Lineweaver.
So here we are, according to the theory, the last ones standing. Lonely, but undoubtedly lucky. Don’t celebrate just yet, though, because Stephen Hawking has concerns we might not last the 21st century…
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