How would do you recognize another Earth while you’re on this one?
That’s a question astronomers often try to answer. Oh, the scientists say, they could look at orbital models, temperature models, atmospheric models, formation models. All kinds of models. “None of these models include anything like pollution or warfare or any of the things that make Earth a human world,” says Lisa Messeri, an anthropologist of science and technology. There was a striving quality to their answers.
“We don’t want to find a world with warfare or stricken with poverty,” Messeri says. We want a perfect world, she continues, “a world that is untouched by human activity.”
Messeri herself doesn’t study these great-beyond planets: She studies the people who study them. And in their presentations, papers, and talk amongst themselves Messeri notices a few things: that the astronomers have turned these light-years-away planets into real places—not just plots and pixels—defined in comparison and contrast to this terra firma. Most importantly, though, Messeri sees evidence that while exoplanet science is a field of the present and future, it also reaches, fundamentally, toward the past.
The astronomers Messeri studies often spend their lives searching for so-called Earth-like planets. These worlds could potentially have life. They could have liquid water or continents or oxygenated air. They’re the right sizes at the right distances from their suns, and could have the right atmospheres and oceans. We sometimes call this search one for “Earth’s twin.”
But that’s not quite right, Messeri says: It’s actually the search for Earth’s perfect twin. Earth as it used to be, before humans got to it. A whole-world Eden.
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