The Year's Best Science Fiction, Vol. 20

I hadn’t walked away, though. And even if the decision had come down to the wire, why shouldn’t I be proud that I’d made the right choice? That didn’t mean everything that followed was tainted, like a reward from some sleazy, palm-greasing deity. I hadn’t won Francine’s affection in a medieval test of bravery; we’d chosen each other, and persisted with that choice, for a thousand complicated reasons.

We were together now; that was what mattered. I wasn’t going to dwell on the path that had brought me to her, just to dredge up all the doubts and insecurities that had almost kept us apart.

2012

As we drove the last kilometre along the road south from Ar Rafidiyah, I could see the Wall of Foam glistening ahead of us in the morning sunlight. Insubstantial as a pile of soap bubbles, but still intact, after six weeks.

“I can’t believe it’s lasted this long,” I told Sadiq.

“You didn’t trust the models?”

“Fuck, no. Every week, I thought we’d come over the hill and there’d be nothing but a shrivelled-up cobweb.”

Sadiq smiled. “So you had no faith in my calculations?”

“Don’t take it personally. There were a lot of things we could have both got wrong.”

Sadiq pulled off the road. His students, Hassan and Rashid, had climbed off the back of the truck and started towards the Wall before I’d even got my face mask on. Sadiq called them back, and made them put on plastic boots and paper suits over their clothes, while the two of us did the same. We didn’t usually bother with this much protection, but today was different.

Close up, the Wall almost vanished: all you noticed were isolated, rainbow-fringed reflections, drifting at a leisurely pace across the otherwise invisible film as water redistributed itself, following waves induced in the membrane by the interplay of air pressure, thermal gradients, and surface tension. These images might easily have been separate objects, scraps of translucent plastic blowing around above the desert, held aloft by a breeze too faint to detect at ground level.

The further away you looked, though, the more crowded the hints of light became, and the less plausible any alternative hypothesis that denied the Wall its integrity. It stretched for a kilometre along the edge of the desert, and rose an uneven 15 to 20 metres into the air. But it was merely the first, and smallest, of its kind, and the time had come to put it on the back of the truck and drive it all the way back to Basra.

Sadiq took a spray can of reagent from the cabin, and shook it as he walked down the embankment. I followed him, my heart in my mouth. The Wall had not dried out; it had not been torn apart or blown away, but there was still plenty of room for failure.

Sadiq reached up and sprayed what appeared from my vantage to be thin air, but I could see the fine mist of droplets strike the membrane. A breathy susurration rose up, like the sound from a steam iron, and I felt a faint warm dampness before the first silken threads appeared, crisscrossing the region where the polymer from which the Wall was built had begun to shift conformations. In one state, the polymer was soluble, exposing hydrophilic groups of atoms that bound water into narrow sheets of feather-light gel. Now, triggered by the reagent and powered by sunlight, it was tucking these groups into slick, oily cages, and expelling every molecule of water, transforming the gel into a desiccated web.

I just hoped it wasn’t expelling anything else.

As the lacy net began to fall in folds at his feet, Hassan said something in Arabic, disgusted and amused. My grasp of the language remained patchy; Sadiq translated for me, his voice muffled by his face mask: “He says probably most of the weight of the thing will be dead insects.” He shooed the youths back towards the truck before following himself, as the wind blew a glistening curtain over our heads. It descended far too slowly to trap us, but I hastened up the slope.

We watched from the truck as the Wall came down, the wave of dehydration propagating along its length. If the gel had been an elusive sight close up, the residue was entirely invisible in the distance; there was less substance to it than a very long pantyhose-albeit, pantyhose clogged with gnats.

The smart polymer was the invention of Sonja Helvig, a Norwegian chemist; I’d tweaked her original design for this application. Sadiq and his students were civil engineers, responsible for scaling everything up to the point where it could have a practical benefit. On those terms, this experiment was still nothing but a minor field trial.

I turned to Sadiq. “You did some mine clearance once, didn’t you?”

“Years ago.” Before I could say anything more, he’d caught my drift. “You’re thinking that might have been more satisfying? Bang, and it’s gone, the proof is there in front of you?”

“One less mine, one less bomblet,” I said. “However many thousands there were to deal with, at least you could tick each one off as a definite achievement.”