by Doug Franklin
Doug Franklin gives us a thorough rundown of the science that inspired his latest story, “The Origami Man,” from our [Jan/Feb issue, on sale now!]
Stories come from somewhere, as Jerry says in “The Origami Man.” This story’s origins are hard to see in the final product. Back in 2015, I was fascinated by observations of Tabby’s Star, which showed non-periodic fluctuations in brightness. The web lit up with talk of alien megastructures, but what I saw in my mind’s eye was a fleet of alien light sails casting ominous shadows upon us as they bore down on Earth. Fun stuff—it would make a great Halloween movie poster—but could it actually work?
The idea is complicated by the nature of interstellar trajectories: stars move relative to each other, and they are very far apart. Imagine shooting an arrow at a rapidly moving target—a bird in flight, your neighbor’s pesky drone—whatever pleases your sensibilities. If you aim at where the target is, then when you release the arrow, it will cross the target’s path far behind it. To hit the target you must aim well ahead of where you see it. On top of this, you have the problem of light lag. Tabby’s Star is 1470 lightyears away, so when our hypothetical aliens shoot an arrow at us, they’ll also have to factor in that we are 1470 years—multiplied by our relative speed—away from where they see us.
In this case the arrow is a light sail, driven forward by the light emitted by its origin star, or if our aliens are serious about getting here before their civilization ages out, a laser beam. Either way, photons from the light sail’s origin hit it and bounce back, transferring momentum and propelling the sail forward, and casting a shadow along the same line. Unfortunately for my Tabby’s Star story idea, when relative motion and light lag are taken into account, for most of its journey the shadow of the lightsail is going to be projected far ahead of the line between its origin and its destination. So the fleet’s shadows would not occlude Tabby’s Star from our perspective, at least not until the light sails were pretty much on top of us, when all the angles converge.
And that’s kind of interesting. Are alien light sails about to arrive? Have they already blown by us? Maybe? I didn’t get around to doing the math before evidence emerged that contradicted the idea of solid objects in the vicinity of Tabby’s Star casting black shadows. Instead, different wavelengths are filtered at different amplitudes, which strongly implies a dust cloud. So I set the idea aside and got on with writing my novel The Extrapolated Man, which if you’re reading this, you’d probably like. Just saying.
Set aside, yes, forgotten, no. A piece fell into place when Project Starshot hit the news in 2016. Their big idea was to shrink interstellar probes down to the size of insects, shoot a swarm of them into orbit with a conventional rocket, and then drive them up to 20% of lightspeed with ground-based lasers.
Then in 2017, MIT News published an article about an algorithm developed by Erik Demaine and Tomohiro Tachi that could fold a flat sheet into any three-dimensional shape. A flat sheet lik . . . a light sail? That would be a cool way for our hypothetical extra-terrestrials to design an interstellar probe! Drive a light sail across the void, then fold it into a shape that allows it to explore whatever environment it finds at the end of the journey.
One more vital piece was still missing. How would our E.T. phone home? For that I needed a high-gain interstellar communication network. Fast forward to 2022, when Les Johnson published a slim book titled A Traveler’s Guide to the Stars, which among other topics discusses building a solar gravitational lens telescope to observe other star systems.
Gravitational lenses are well-established natural phenomena wherein a massive object between us and a distant star bends the light from that star around it and produces a magnified image. Google up Einstein Cross when you’ve got a minute. Anyway, Johnson writes about using our sun’s gravity as the lens. Place a telescope 540 astronomical units away from the sun—way past the Kuiper Belt, out in the scattered disk—on the opposite side of the sun from the star system you want to look at, and it will be able to image Earth-sized planets in fantastic detail. We’re talking city lights from a hundred lightyears.
So let’s put that shoe on the other foot. What if aliens parked a satellite in our solar system at the sun’s gravitational lens point, such that it could detect highly-magnified signals from its origin? And also send highly-magnified signals back to it, right? Because light rays bend the same coming or going. Since our aliens are in the interstellar exploration business, no doubt they would park a telescope in a similar position near their own star. So they’d be able to see not just our city lights, but greatly magnified signals from their probe.
With that, I finally had all the technical bits to make the story work: light sails that fold themselves into probes upon arrival, and with a little extra infrastructure, communicate with their origin. The only significant departure I made in “The Origami Man” was to cast back forty years to Robert Forward’s pioneering work on the intellectual precursor to Project Starshot. Forward designed “starwisps” propelled by coherent microwaves instead of lasers. A starwisp is made of wire mesh that reflects radio waves, with processor nodes at each intersection of the wire from which it is woven. Which fit nicely, I thought, with the idea of something that could fold itself, if each of those nodes were microscopic robots pulling on the starwisp’s rigging like tiny sailors.
In any case, with each layer of research, I got a little further from the basic inspiration of light sails arriving from Tabby’s Star. The interstellar communication network put the final nail in that story’s coffin. For reasons that ultimately had nothing to do with the story, but with the novel I had recently finished and its pending sequel, I wanted communication between the probes and their origin to take place on the scale of human lifespans. At 1470 lightyears away, Tabby’s Star was just too far to work. Tau Ceti, on the other hand, is a mere twelve lightyears away . . .
Some authors create whole new universes for each of their stories. Ted Chiang comes to mind. That guy! But I find myself following the tracks left by Robert Heinlein and Larry Niven. Both were huge influences on me when I was young. I clearly remember how much pleasure I got out of Niven’s Known Space stories as a teenager, and Robert Heinlein’s rich—if somewhat less cohesive —Future History before that. And at the end of the day, I write stories that I would like to read. So without dropping any spoilers, I will say that the events in “The Origami Man” are an integral part of the bigger story told by The Extrapolated Man and its sequel, whose working title is Gaia’s Daughter.
For those who find the cultural aspects of stories as interesting as the nuts and bolts, my conception of kushtakas came from Shamans and Kushtakas: North Coast Tales of the Supernatural by Mary Giraudo Beck. There are intriguing similarities between the kushtakas of the North Pacific and the selkies of the North Atlantic. It makes me wonder; why do we have so many shapeshifter myths? Sure, it’s probably because roughly one percent of the population is psychopathic. Who hasn’t had that horrible moment of realizing the person across the table is not who you thought they were? The mask slips, and we see what’s beneath it. So it’s probably that. But I do love stories where it turns out there’s a physical reason for the weirdness. (In this regard, I have to recommend Peter Watt’s Blindsight. Peter, if you’re reading this, please write more. I miss you in my brain.)
Life as No One Knows It bytheoretical physicistSara Imari Walker shaped my ideas about the motivations of the aliens. Walker makes a compelling argument that life on Earth is a very large object in time that has taken billions of years to self-assemble. I think that aliens with the capacity for interstellar exploration, with its millennium-scale missions, would have a sense of this temporal extent, and would value it. They would not want to eat us, or enslave us, or even talk to us. Humanity is only 300,000 years in extent. What they would care about, I think, is documenting the biosphere itself, an utterly unique structure four billion years in extent, before humanity burns it down.
The Astounding Analog Companion 