2312

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

Decoherence happens at the loss of superposition and the resulting either/or. Before that a quantum calculation performs in parallel every possible value that the register can represent

Using superposition for computation requires avoiding decoherence for as long as possible. This has proved difficult and is still the limiting factor in the size and power of a quantum computer. Various physical and chemical means for building and connecting qubits have increased the number of qubits possible to connect before decoherence collapses the calculation, but

Quantum computers are restricted to calculations that can be performed faster than decoherence occurs in the superposed wave functions. For over a century this restricted time for a quantum computing operation to less than ten seconds

Qubes are room-temperature quantum computers with thirty qubits, the decoherence boundary limit for circuit-connected qubits, combined with a petaflop-speed classical computer to stabilize operations and provide a database. The most powerful qubes are theoretically capable of calculating the movements of all the atoms in the sun and its solar system out to the edge of the solar wind