Iterations and other stories (collection)

“Oh, yeah,” said Dalt. “I guess it is.” He pointed at it, too. I couldn’t see anything, but it seemed in the darkness that if I could draw lines from the two children’s outstretched fingers, they would converge at infinity.

Dr. Tadders was an old friend, and with both Suzto and Dalt seeing the lights, I decided to join her for lunch. We grew wheat, corn, and other crops under lamps here on the outside of the sphere, and raised chickens and pigs; if you wanted the eggs to hatch, you had to put low roofs over the hens, because they needed to be in constant contact with their clutches, and their own body movements were enough to propel them into flight; chickens really seemed to love flying. Tadders and I both knew that we’d have had more interesting meals if we’d stayed inside the sphere, but the ancient texts said that although the interior was huge, there was still much, much more to the universe.

Most of those on the interior didn’t care about such things; they knew that the sphere’s inner surface could accommodate over a million trillion human beings—a vastly larger number than the current population—and that our ancestors had shut us off from the rest of the universe for a reason. But some of us had decided to venture outside, starting a new settlement on our world’s only real frontier. I didn’t miss much about the inside—but I did miss the food.

“All right, Rodal,” Dr. Tadders said, gesturing with a sandwich triangle, “here’s what I think is happening.” She took a deep breath, as if reviewing her thoughts once more before giving them voice, then: “We know that a long, long time ago, our ancestors built a double-walled shell around our sun. The outer wall is opaque, and the inner wall, fifty bodylengths above that, is transparent. The area between the two walls is the habitat, where all those who still live on the interior of the sphere reside.”

I nodded, and kicked gently off the floor to keep myself afloat. We drifted out of the dining hall, heading outdoors.

“Well,” she continued, “we also know that there was a war generations ago that knocked humanity back into a primitive state. We’ve been rebuilding our civilization for a long time, but we’re nowhere near as advanced as our ancestors who constructed our world were.”

That was certainly true. “So?”

“So, what about that story you translated a while ago? The one about where we supposedly came from?”

I’d found a story in the ancient computers that claimed that before we lived on the interior of the Dyson sphere, our ancestors had made their home on the outer surface of a small, solid, rocky globe. “But that was probably just a myth,” I said.

“I mean, such a globe would have been impossibly tiny. The myth said the homeworld was six million bodylengths in diameter. Kobost”—a physicist in our community—“worked out that if it were made of the elements the myth described, even a globe that small would have had a crushingly huge gravitational attraction: live bodylengths per heartbeat squared. That’s more than ten thousand times what we experience here.”

Of course, the gravitational attraction on any point on the interior of a hollow sphere is zero. When we lived inside the sphere, the only gravity we felt was the pull from our sun, gentiy tugging things upwards. Here, on the outside of the sphere, the gravitational pull is downward, toward the sphere’s surface—and the sun at its center.

I continued. “Although Kobost thinks human muscle could perhaps be built up enough to withstand such an overwhelming gravity, his own studies prove that the globe described in the myth can’t be our homeworld.”

“Why not?” asked Tadders.

“Because of the chickens. There are several ancient texts that show that chickens have been essentially the same since before our ancestors built the Dyson sphere. But with an acceleration due to gravity of five bodylengths per heartbeat squared, their wings wouldn’t be strong enough to let them fly. So that globe in the myth couldn’t possibly have been our ancestral home.” “Well, I agree that’s puzzling about the chickens,” said Tadders, “but wherever our ancestors came from, you have to admit it wasn’t another Dyson sphere. And the inside of a Dyson sphere forms a very special kind of sky. Remember what it was like when we lived in there? Wherever you looked over your head, you saw—well, you saw the sun, of course, if you looked directly overhead. But everywhere else, you saw other parts of the sphere. Some of those parts are a long, long way off—the far side of the sphere is a hundred and fifty billion bodylengths away, isn’t it? But, regardless, wherever you looked, you saw either the sun or the surface of the sphere.”

“So?”

“So the surface of the sphere is reflective—even the dull, grass-covered parts reflect back a lot of light. Indeed, on average the surface reflects back about a third of the light it receives from the sun, making the whole sky glaringly bright.”