Free Galileo's Dream by Kim Stanley Robinson

white towers, an arc of pale aquamarine appeared across the whiteness. The stranger led him to this arc, which proved to be a broad rampway cut into the ice, dropping at a very slight angle, down to where it cut under an arch or doorway into a long wide chamber.
    They descended. The chamber under the ice roof had broad white doors, like city gates. At the bottom of the ramp they waited before these. Then the gates went transparent, and a group of people dressed in blouses and pantaloons of Jovian hues stood before them, in what seemed a kind of vestibule. The stranger touched Galileo lightly on the back of the arm, and led him into this antechamber. They passed under another arch. The group fell in behind them without a word. Their faces appeared old but young. The space of the room made a gentle curve to the left, and beyond that they came to a kind of overlook, with broad steps descending before them. From there they could see an entire cavern city stretching to the near horizon, all of it tinted a greenish blue, under a high ceiling of opaque ice of the same color. The light was subdued, but more than enough to see by; it was quite a bit brighter than the light of the full moon on Earth. A hum or distant roar filled his ears.
    â€œBlue light goes farthest,” Galileo ventured, thinking of the distant Alps on a clear day.
    â€œNo,” the stranger said. “The different colors are waves of different lengths, red longer, blue shorter. The shorter the wavelength, the more light tends to bounce off things, even ice or water, or air.”
    â€œA pretty color,” Galileo said, surprised, trying to think what the stranger meant when he said that light moved in waves, and whether that might account for some of the optical bounce between two lenses that he had noted in their work on the glass.
    â€œI suppose it is. They illuminate some spaces in here with artificial light sources, to make things brighter and give them the full spectrum.” He indicated a building that glowed like a yellow lantern in the distance. “But mostly they leave it like this.”
    â€œIt makes you look like angels.”
    â€œYet we are only people, as I’m afraid you will soon learn.”

    The stranger led him to an amphitheater, sunk into the surface of the city floor so that it was not visible until they came to the curved rim of the highest seats. Looking down into it, Galileo saw resemblances to Roman theaters he had seen. The bottom dozen rows of seats were occupied, and there were other people standing on the round stage. They all wore loose blouses and pantaloons that were blue, pale yellow, or the Jovian tones of Galileo’s group. At the center of the stage, a white glowing sphere stood on a pedestal. Faint black lines crisscrossing it gave Galileo the impression that it might be a globe representing the moon they stood on.
    â€œThe council?” Galileo asked.
    â€œYes.”
    â€œWhat would you have me say?”
    â€œSpeak as the first scientist. Tell them not to kill what they study. Nor to kill themselves by studying it.”
    The stranger led Galileo down steps into the amphitheater, now firmly holding him by the upper arm. Galileo felt again the strange lack of his proper weight; he bounced as he would have if standing neck-deep in a lake.
    The stranger stopped several steps above the group and made a loud announcement in a language Galileo did not recognize. Only slightly delayed, he also heard the man’s voice say in Latin, “I present to you Galileo Galilei, the first scientist.”
    Everyone looked up at them. For a moment they were motionless, and many of them looked startled, even disapproving.
    â€œThey look surprised to see us,” Galileo noted.
    The stranger nodded. “They want to be sheep, and so should be sheepish. Come on.”
    As they descended farther, some of the ones dressed in orange or yellow bowed. Galileo bowed in return, as he would have before the