Learning the World

“Neat,” he said. The electric light was fading and yellowing by the minute. “Let’s look at it outside.”

They squatted in the cave mouth, leaning back on the mesh doorway, facing an abyss of air, a shimmer of grassland, a horizon line of sea. Darvin felt his every muscle and nerve sing with relief.

“I don’t believe the cliff-men lived in caves at all,” he said. “They’re just too horrible.”

“That is a widespread scientific opinion,” said Orro. “They left their dead in them, or perhaps just their illustrious dead; they may have used the places as stores, or as places of worship and meditation; but the popular belief that they inhabited caves is ill-founded.”

“I’m glad to hear it,” said Darvin. He sighed; he was almost reluctant, now, to at last find out whether his own expectation of the caves was ill-founded. “Well, let’s see what we’ve got.”

He unfolded three pieces of paper: his tracing of the photograph, his sketch of the silk map, and his tracing of the antique woodcut. He spread them on the ground and weighted them with pebbles, then placed the notebook, open at Orro’s sketch, beside them. The patterns were not quite identical, and not all the stars shown in one were shown in the others, but as he looked from one drawing to the next, and back, again and again, it was obvious that they were all of the same familiar patch of sky.

The evidence before his eyes was as clear as the jump on a blink comparator: the cliff-men had recorded seven of the stars in the Daughters as green, and the rest as other colours.

“You were right,” he said. “We have a trend.”

He closed his eyes for a moment, and saw a drifting fleet of dots, as if the images he’d looked at were resonating in his optic nerves, fainter and more persistent than an afterimage. He blinked it away and gazed out at the sky.

“In prehistory, the cliff-men saw seven green Daughters. In antiquity, the astrologers of the South saw twenty-seven. In the Dawn Age, mere eights-of-eights of years ago, forty-nine. In the present day, we see fifty-eight with the naked eye, and more with telescopes. And it’s not that some are brighter now than they were then — our ancestors saw stars in the same positions, and saw them as red, yellow, or white. These stars have changed from other colours to green, in the lifetime of the human race.”

Orro jumped up and stalked about for a moment, to the very lip of the cave and back. “Stars evolve,” he said. “From white to yellow to red, isn’t it?”

“I know of that hypothesis,” said Darvin. “The fire analogy. It’s speculative, and going from every other colour to green would knock it right on the head.”

“Not necessarily,” said Orro. “If the green represents a different evolution: life spreading from star to star.”

“Ah, the comet plants!” said Darvin. “The vacuum forests!”

Orro shrugged. “Life is adaptable.” He glared down at Darvin. “You are testing me with your scepticism. You do not feel it yourself.”

“No,” said Darvin. “I don’t.” He folded the sheets of paper between the pages of the notebook and tucked it away. “Tell me what you suspect I suspect.”

Orro squatted down again. “Isn’t it obvious? You suspect that the green tinge is caused by life, yes, but by life in some artificial environment.” He outlined a circle with his hands. “Great globes of glass, perhaps, somehow launched into space, containing complete economies of nature, plants and animals alike, and whatever intelligent inhabitants have built them. That they multiply around a sun, to the extent that eventually they filter all of its light. And that as each sun’s environs become crowded, great ships are launched across the voids between the stars, to repeat the process around another sun. Your comet is of course such a ship, decelerating into orbit around the Sun Himself. In years to come, our sky will be crowded with the green globes, and we ourselves may look forward to meeting the mighty builders of worlds, should they deign to notice such as us.”

Darvin looked sidelong at his friend with admiration. “What a delightful fancy!” he said. “No, really. And it is a possibility, I concede. But as scientists rather than writers of engineering tales, we should seek explanations in the work of nature rather than the hand of mind whenever possible. I think it’s life, certainly, and that it is spreading, but I think it may be an entirely natural process. Because if life — a hardy spore that escaped the atmosphere, perhaps — were to gain a foothold on some rock or comet in space, it could spread. As it did so it would be modified by evolution, and its own actions would modify the paths of the bodies on which it grew. A decelerating comet seems much more plausible if we imagine its out-gassing to be controlled — mindlessly, it is true — by some life within.”

Orro was shaking his head. “A journey from star to star would take millions of years. We’re seeing stars changing over eights-of-eights.”

“I’m not talking about passive drifting, like spores or downy seeds on the wind. I imagine some much faster propulsion.” He swept his arms in a circle wider than the one Orro had outlined a moment earlier. “A sail of some sort.”

“Propelled by what wind?”

“Light exerts a pressure in vacuum,” said Darvin. “The Sun gives forth a fiery stream of other particles.”

“Too weak a one for star-sailing,” Orro said. “No, Darvin, we are looking at… spaceships. And artificial worlds in numbers that beggar the imagination.”

Darvin felt his knees shake. He did and did not want to believe it.

Orro took two strips of dried meat from his provisions pack, passed one to Darvin and started chewing on the other. “Here is an idea for further research. We find out the distance of each of the stars charted in the Daughters region, green or not. We can see whether the earlier green stars are closer together than the later ones. From this we can see if a spread from star to star is actually happening.”

Darvin nodded. “Obvious,” he said. “Go on.”

“And we check whether spectrographic analyses exist for any of these stars. If we were to find that they still show traces of the spectra from stars with lights of other colours than green and they match the ancient records, we’d have made our case. And then we should find out the composition of the green light itself.”

“Oh, I know what that is,” said Darvin. “Its spectra show the lines of oxygen, carbon, and nitrogen.”

Orro jumped up again. “But these are the constituents of life itself!”

“Yes,” said Darvin. “And that’s one reason why astronomers regard life around these stars as possible. That is not the surprise. The surprise, if we are right, is that we have evidence that it is spreading. Or at least,” he added, struck by an intellectual scruple, “that it is arising around more and more stars.”

“Why has more not been made of this?” Orro almost shouted. “Life around the stars would be the most significant finding of astronomy!”

Darvin thought about it, chewing on the strip. “Hmm,” he said. “I suppose because it’s all so wretched hypothetical, old chap, and so embarrassing to seem to confirm the myths of religion and the… sensationalism of the vulgar.”

He smiled at Orro and gestured at him to sit down. “Let’s eat,” he said. “And then let’s take wing, and fly over the high desert, and find some place of comfortable vantage to wait for nightfall and count the Daughters for ourselves.”

It goes all the way down, Darvin thought to himself. Out here in the pitch black of a night before either of the moons had risen, away from lights and smoke, the sky came all the way down to the ground. You could see stars blink into view as they rose above the horizon, and to the west you could watch them disappear beneath it. And in between, in the vault above, the sky was packed with stars. The whole sky shimmered with the massed twinkling in multiple colours. The Shining Path spa