So he said nothing beyond a simple acceptance of the assignment.

At which point the Satyr of Pan stood to speak. “You must tell us if you think this effort will make trouble for the other projects Alex had going. Can you remind the council what’s at stake here, and how those projects are going in her absence?”

Wahram nodded stiffly as he thought over his response. He and the other Alexandrines were attempting to keep a low profile, and some of the council members had not paid enough attention to notice their projects’ authorization and budgeting inside larger expenditures. “Alex kept things separate in her calculations, so that won’t be a problem for us. Some other matters are being dealt with by a group centered around Wang and Inspector Jean Genette. We would need to go under a cone of silence to discuss all this in detail, but suffice it to say, Alex was heavily involved with a Mondragon project to help Earth cope with its various problems by ecological means. A lot of the terraria in the Mondragon are working on that, it has its own momentum, and we’ve agreed to help them. Then also there is an investigation going on into the role of qubes in some questionable activities, on Mars, Venus, Io, and elsewhere. This also will proceed no matter what happens with the Vulcanoids, which is only an above and beyond, although admittedly an important one.”

The council, not wanting to retire into the cone and be cut off from the cloud and radio, adjourned the meeting. Wahram returned to his room. His crèche kept an apartment in a little block of apartments, all clustered around a square that was occupied almost entirely by Titans, with Titanic shops and restaurants. There he lived among his crèchemates and enjoyed their support, which was so benign and understanding that life there much resembled living in complete solitude. As the days passed before the spaceliner that would take him downsystem arrived, he walked the city spine to the council meetings, he followed the work on Titan in daily consultations, and he did his share of Iapetus work in the kitchen of the dining hall on the ground floor of their building. He attended a concert series, joined the little group of musicians in the park, filled and emptied dishwashers. As he dodged diners and servers in the hall, the repeated minuscule navigational challenges reminded him of Proust’s comparison of a restaurant in action with the whirling planets of the solar system, which had struck him as fanciful (not to mention quite a scale shift between vehicle and tenor) until he had seen it for himself, in restaurant after restaurant: their affairs were elaborations of the second law of thermodynamics, Beckian diffusions of energy through the universe, and around they went in the great orrery of their lives. Soon he would descend sunward and seek out the Mercurial.

But then she called him. She was coming to Saturn, with Jean Genette; they wanted to descend into the clouds of Saturn to look for a spaceship possibly adrift in the big beauty’s upper layers. She wanted him to arrange the dive into Saturn, if possible, and then join them in it.

“That would be fine,” he replied; “I am at your disposal.” Which was certainly one way of putting it.

Lists (8)

Prometheus, Pandora, Janus, Epimetheus, and Mimas; these are the moons that shepherd Saturn’s rings.

The rings are only 400 million years old, the result of a passing Kuiper belt ice asteroid being stripped to its core when it passed Saturn too closely.

Mimas, the bull’s-eye moon, is 400 kilometers in diameter, while its crater Herschel is 140. The Herschel impact nearly blew Mimas apart.

Hyperion is a fragment of a similar collision that did blow a moon apart; it is shaped like a hockey puck. The impact caused flash steam explosions across a plane and split the moon as if spalling granite. The facet left behind is pocked like a wasps’ nest by a field of rimless dust-filled craters.

Pandora is shaped like a jelly bean.

Tethys and Dione were both about 1,100 kilometers across (think France), both fractured all over their surfaces, etched by canyons with mile-high walls. Tethys’s Ithaca Chasma is twice as deep and four times as long as the Grand Canyon, and a thousand times older, very battered by Saturn’s everlasting civil wars.

Dione, on the other hand, was disassembled by self-replicating ice cutters in the 2110s, and the Hector-sized segments were then directed downsystem to Venus. They struck Venus on a line parallel to the equator and provided Venus with a deep ocean bed and the water to fill it, while also knocking a good bit of the choking Venusian atmosphere off into space.

Rhea is as wide as Alaska, with the usual plethora of craters, including fresh ones that throw bright ice rays out from their centers.

Iapetus orbits seventeen degrees out of the plane of Saturn’s equator and thus has one of the best views of the rings; is therefore popular. The bulge is the biggest city in the Saturnian system.

Epimetheus is a misshapen pile of loosely consolidated rubble. It switches orbits with the moon Janus every eight years; they are co-orbital moons, very rare—a sign of past impacts.

Enceladus is covered by braided spills of ice. No craters—the ice surface is too new, as it is continuously resurfaced from the liquid-water ocean in the depths. Heat sources boil some of this carbonized water, creating geysers that shoot many kilometers into space. The water quickly freezes in its flight, and some of it makes it up to the slender E ring; the rest falls back down and under its own weight turns to firn and then back to ice again. A suite of microscopic life-forms was discovered in the Enceladan ocean in the year 2244, and scientific stations have been established on its surface, as well as a cult of votaries who ingest a suite of the alien life-forms, to unknown effect.

There are twenty-six irregular small moons. These are all Kuiper belt objects, captured as they crossed Saturn’s earliest gas envelope. Phoebe, at 220 kilometers across, is the largest of these, and it has a retrograde and highly inclined orbit, twenty-six degrees out of the plane; thus another popular viewing platform.

Titan, by far the largest Saturnian moon, is bigger than Mercury or Pluto. More about Titan later.

Extracts (9)

One question for computability: is the problem capable of producing a result

If a finite number of steps will produce an answer, it is a problem that can be solved by a Turing machine

Is the universe itself the equivalent of a Turing machine? This is not yet clear

Turing machines can’t always tell when the result has been obtained. No oracle machine is capable of solving its own halting problem

A Turing jump operator assigns to each problem X a successively harder problem, X prime. Setting a Turing machine the problem of making its own Turing jump creates a recursive effect called the Ouroboros

All problems solvable by quantum computers are also solvable by classical computers. Making use of quantum mechanical phenomena only increases speed of operation

two popular physical mechanisms, dots and liquids. Quantum dots are electrons trapped inside a cage of atoms, then excited by laser beams to superposed positions, then pushed to one state or the other. Quantum liquids (often caffeine molecules because of the many nuclei in them) are magnetically forced to spin all their nuclei in the same spin state; then NMR techniques detect and flip the spins