“Hey,” Galileo said, shocked. “What happened to your teletrasporta?”
Ganymede tilted his head. “All that was done to give you a way to comprehend what was happening. It was felt that if you were bilocated without some way to explain the prolepsis to yourself from within your own frame of reference, you might be excessively disoriented. Some feared you would experience a mental breakdown, or otherwise fail to accept the reality of the prolepsis. Perhaps assume you were dreaming a dream. So we constructed a simulacrum of a translation that would make sense in local terms—in your case, a flight through space. We made the entangler look like something that could cast your vision to us. Then the experience of flight was given to you after you had already been bilocated.”
“You can do that?”
The stranger gave Galileo a pitying look. “Simulated experiences can sometimes be distinguished from real ones, but in data-poor environments, like space, it’s hard to do.”
Galileo gestured at the great ice cavern extending away from them in every direction, its aquamarine roof starred by cracks. “If this cave were not real, how would I tell?”
Ganymede shrugged. “Maybe you couldn’t.”
“I thought not,” Galileo muttered. “These are all dreamscapes.” He thought again of his immolation at the stake. More loudly: “What keeps us warm?”
“Heat.”
“Bah. Where comes the heat? Where comes the air?”
“There are engines creating them.”
“Engines?”
“Machines. Devices.”
“So illuminating!”
“Sorry. The details would mean nothing to you. Very few people here understand them. The heat and air are simple, in any case. It’s protection from Jupiter’s radiation that is difficult. That’s why we stay below the surface most of the time when on Europa. One of the reasons they’ve gone mad, if you ask me. On Ganymede we were out under the sky. On Io, we take advantage of the new bubble fields. But here they have older structures for dealing with the problem.”
“Radiation? Isn’t that another name for heat?”
“Well, but there are vibrations along a spectrum of sizes. What our eyes see are wavelengths of a certain size, but that band of the visible is just part of a range that extends far to either side. Shortest are gamma waves, then longer wavelengths range from braccia to the width of the universe, more or less.”
Galileo stared at him. “And these other waves manifest as?”
“Heat, sometimes. Damage to flesh that can’t be felt. I don’t know exactly how to explain it to you.”
Galileo rolled his eyes. “Then take me to someone who can.”
“We don’t actually have time for that, sorry—”
“Take me to someone who knows! Because you are an idiot.”
Ganymede rolled his eyes. “I forbear—”
“Take me!” Galileo shouted, and shoved the man hard in the chest. At home he would have beat him, so why not here? He wasn’t convinced any of it was real. He kicked Ganymede in the shins, yelling fit to turn all the blues of the place red. “Come on! Someone who knows something. Surely there must be someone who knows something!” He raised his big fist.
“Stop it,” Ganymede complained. He was wispy despite his height, and looked confused to be assaulted. “Quit trying to bully me. We aren’t in one of your downriver alleys here. People will notice what you do, and conclude you aren’t really civilized.”
“Me? It’s you who are uncivilized. You don’t know even the basics of how your machines work.”
“Spare me. No one knows all these things. Could you tell me how every machine of your time worked?”
“Yes, of course. Why not?”
Ganymede pursed his lips. “Well, it is no longer possible.”
“I don’t accept that. The principles at least must be clear, if you make the attempt to understand.”
“You’ll see.” And he muttered to the side, as if to an invisible angel.
“Take me.”
“I’ll take you.”
The gallery they were in was a kind of giant open antechamber to another under-ice city. Broad spaces extended so many miles away from them that in the distance the blue ceiling curved down and met the floor, cutting off any farther sight. Picking out one particular bright silver building ahead of them, just where the ceiling appeared to meet the floor, Galileo found it took only about fifteen or twenty minutes to walk to it. A close horizon. The alleys and strada of this cold town were sometimes crowded with tall graceful people, moving as if in water; at other times the streets were nearly empty. The people wore clothing like Ganymede’s, simple but fine, warm pastel tones making them appear illuminated in the green light.
They continued beyond the silver building for about an hour, he reckoned, passing crowded plazas extending to left and right, some of them open to the black sky, most roofed by ice. As the hour passed, he learned better how to walk in the light downward pull. This strange lightness was suggestive of all kinds of things, including the idea that weight was perhaps proportional to the size of the planet one stood on. Another sign that Europa must be fairly small.
“Where are you taking me?” he said.
“To a person who may be able to answer your questions. Or maybe you would call it a machine.”
“A machine? So none of you know?”
“No no, this person is a kind of … composite. A person quite like you, in fact—a physicist and mathematician, quite famous.”
“Good,” Galileo said. “I want some explanations.”
They came to a lake, and stepped down into a long low boat, like a gondola. When they were settled in its bow, a boatman cast off and they hummed slowly over clear blue water, leaving a wake that ran in a clean curl that was slower than it would have been on the lagoon. Greenish blues pulsed overhead and in waves around them, and Galileo could not tell how deep the lake might be, as the many subtle shades of creamy blue bobbed darker and lighter, but always opaque. Royal blue, sky blue, azure, turquoise, aquamarine—all these bounced against each other in long bands, and it also seemed that waves of cobalt were passing through the other blues, staining them as it pulsed by, as if they boated through the veins of a beating blue heart. The buildings behind the broad fondamenta to their left looked like clean blocks of ice, painted in pastels that held their color manfully even in the omnipresent green-blue glow, contradicting what Galileo thought he knew of color theory. The sight of one curving row of waterfront buildings reminded Galileo strongly of the Grand Canal, and he saw the city was a kind of Venice carved in ice. “Why doesn’t it melt?”
“It’s all cladded. Sheathed in diamond, in fact.”
People promenaded on the fondamenta just as they would have at home. Some of them looked out on the water, but not at Ganymede and Galileo; theirs was only one watercraft among many. All the wakes on the water created a fine curvilinear slow-motion cross-chop. The ice ceiling overhead was thicker in some places than in others, judging by the differences in the green-blue. Pulses most definitely were running through it.
“What are those waves of color running through the roof?” he asked.
“The other moons exert tidal forces against the tug of Jupiter proper. We shine a type of light through the ice to reveal the stresses in it, so we can see these tides’ interactions.”
“How do you keep these canals and lakes liquid?”
“We heat them,” Ganymede said patiently. “In places you will see steam. In other places we will break through a skim of ice as we progress along certain canals.”
“But you don’t know how the water is heated, do you?”