How We Imagine Aliens

Pop culture’s creations far surpass what science says is possible

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Our world is full of aliens. Ones that we’ve imagined, I mean. Large-headed, large-eyed, silver- or green-skinned visitors on UFOs. E.T. the Extra-Terrestrial’s wide-set eyes, wrinkled brow, and glowing finger. Prosthetic-foreheaded Klingons and prosthetic-eared Vulcans and prosthetic-eared Romulans. Martians who look like humans — lots of aliens who look like humans, actually: four-limbed and upright, except for the ones who are nonorganic beings of pure energy or light. (And the space whales.) They’re psychic or telekinetic or eyeless or faceless, sometimes, but usually not. Especially on screen, they’ll look like us — for the sake of empathy or the simple constraining factor of needing to use human actors. Hence the variety of prosthetics, especially in the decades before computer-generated aliens could join us on screen. (And even then, we missed the prosthetics, in the face of floppy, boneless Jar Jar Binks.)

Whether it’s done by scientists, writers, or visual effects specialists, all our imagining of what aliens look like is just that: imagining. And the bigger, more highly evolved the aliens are that you want to imagine, the bigger the leaps you need to take. Researchers who explore the possibility of microbial life beyond Earth, the different chemistries and microscopic structures that could give rise to life, do so with a practical eye. Their work can offer search parameters to astronomers pointing increasingly sensitive telescopes at planets beyond our solar system, with the chance to detect signs of life — not to mention for researchers designing probes to visit Mars and the possibly habitable moons of the outer solar system. Far fewer scientists spend time thinking about the possible forms of complex life, not just cells that use energy and hold information in DNA or its analogue, but the analogue of animals, the analogue of us.

Aside from the lack of applications for such thought experiments, there just aren’t enough constraints to call that speculation science. Astrophysicist Adam Frank told me, “If you want to use the constraints that science gives you to try and say something about life, then you’re limited to things that are super simple and things that are as complicated as we are.” Frank’s research includes…