“Get a square of metal foil. Pretty much any metal will do. Anodize it until it’s black. Don’t paint it—anodize it. Put clear glass over it and leave a one-centimeter gap between the glass and the foil. Seal the edges with brick, foam, or some other good insulator. Then set it out in the sun.”

“Okay, what good will that do?”

“The black foil will absorb sunlight and get hot. The glass will insulate it from outside air—any heat loss has to pass through the glass, and that’s slow. It’ll reach an equilibrium temperature well over one hundred degrees Celsius.”

I nod. “And at that temperature you can enrich Astrophage.”

“Yes.”

“But it would be ridiculously slow,” I said. “If you had a one-square-meter box and ideal weather conditions… say, one thousand watts per square meter of solar energy…”

“It’s about half a microgram per day,” he said. “Give or take.”

“That’s a far cry from ‘a thousand kilograms’ per day.”

He smiled. “It’s just a matter of how many square meters you make of it.”

“You’d need two trillion square meters to get a thousand kilograms per day.”

“The Sahara Desert is nine trillion square meters.”

My jaw dropped open.

“That went by fast,” said Stratt. “Explain.”

“Well,” I said. “He wants to pave a chunk of the Sahara Desert with blackpanels. Like… a quarter of the entire Sahara Desert!”

“It’d be the biggest thing ever made by humanity,” he said. “It’d be starkly visible from space.”

I glared at him. “And it would destroy the ecology of Africa and probably Europe.”

“Not as much as the coming ice age will.”

Stratt held up her hand. “Dr. Grace. Would it work?”

I fidgeted. “Well, I mean… it’s a sound concept. But I don’t know if it’s even possible to implement. This isn’t like making a building or a road. We’re talking about literally trillions of these things.”

Redell leaned in. “That’s why I designed the blackpanels to be made entirely out of foil, glass, and ceramics. All materials we have plenty of here on Earth.”

“Wait,” I said. “How do the Astrophage breed in this scenario? Your blackpanels will enrich them, sure, and they’ll be breed-ready. But there are a bunch of steps they need to go through when they breed.”