Cities in Flight

ASCREECHING tornado was rocking the Bridge when the alarm sounded; the whole structure shuddered and swayed. This was normal, and Robert Helmuth on Jupiter V barely noticed it. There was always a tornado shaking the Bridge. The whole planet was enswathed in tornadoes and worse.

The scanner on the foreman’s board was given 114 as the sector where the trouble was. That was at the northwestern end of the Bridge, where it broke off, leaving nothing but the raging clouds of ammonia crystals and methane, and a sheer drop thirty miles down to the invisible surface. There were no ultra-phone “eyes” at that end to show a general view of the area—in so far as any general view was possible—because both ends of the Bridge were incomplete.

With a sigh, Helmuth put the beetle into motion. The little car, as flat-bottomed and thin through as a bedbug, got slowly under way on its ball-bearing races, guided and held firmly to the surface of the Bridge by ten close-set flanged rails. Even so, the hydrogen gales made a terrific siren-like shrieking between the edge of the vehicle and the deck, and the impact of the falling drops of ammonia upon the curved roof was as heavy and deafening as a rain of cannon balls. In fact, the drops weighed almost as much as cannon balls there under Jupiter’s two-and-a-half-fold gravity, although they were not much bigger than ordinary raindrops. Every so often, too, there was a blast, accompanied by a dull orange glare, which made the car, the deck, and the Bridge itself buck savagely; even a small shock wave traveled through the incredibly dense atmosphere of the planet like the armor-plate of a bursting battleship.

These blasts were below, however, on the surface. While they shook the structure of the Bridge heavily, they almost never interfered with its functioning. And they could not, in the very nature of things, do Helmuth any harm.

Helmuth, after all, was not on Jupiter—though that was becoming harder and harder for him to bear in mind. Nobody was on Jupiter; had any real damage ever been done to the Bridge, it probably would never have been repaired. There was nobody on Jupiter to repair it; only the machines which were themselves part of the Bridge.

The Bridge was building itself. Massive, alone, and lifeless, it grew in the black deeps of Jupiter.

It had been well planned. From Helmuth’s point of view—that of the scanners on the beetle—almost nothing could be seen of it, for the beetle tracks ran down the center of the deck, and in the darkness and perpetual storm even ultrawave-assisted vision could not penetrate more than a few hundred yards at the most. The width of the Bridge, which no one would ever see, was eleven miles; its height, as incomprehensible to the Bridge gang as a skyscraper to an ant, thirty miles; its length, deliberately unspecified in the plans, fifty-four miles at the moment and still increasing—a squat, colossal structure, built with engineering principles, methods, materials and tools never touched before now ….

For the very good reason that they would have been impossible anywhere else. Most of the Bridge, for instance, was made of ice: a marvelous structural material under a pressure of a million atmospheres, at a temperature of 94° below zero Fahrenheit. Under such conditions, the best structural steel is a friable, talc-like powder, and aluminum becomes a peculiar transparent substance that splits at a tap; water, on the other hand, becomes Ice IV, a dense, opaque white medium which will deform to a heavy stress, but will break only under impacts huge enough to lay whole Earthly cities waste. Never mind that it took millions of megawatts of power to keep the Bridge up and growing every hour of the day; the winds on Jupiter blow at velocities up to twenty-five thousand miles per hour, and will never stop blowing, as they may have been blowing for more than four billion years; there is power enough.

Back home, Helmuth remembered, there had been talk of starting another Bridge on Saturn, and perhaps later still on Uranus too. But that had been politicians’ talk. The Bridge was almost five thousand miles below the visible surface of Jupiter’s atmosphere—luckily in a way, for at the top of that atmosphere the temperature was 76º Fahrenheit colder than it was down by the Bridge, but even with that differential the Bridge’s mechanisms were just barely manageable. The bottom of Saturn’s atmosphere, if the radiosonde readings could be trusted, was just 16,878 miles below the top of the Saturnian clouds one could see through the telescope, and the temperature down there was below —238° F. Under those conditions, even pressure-ice would be immovable, and could not be worked with anything softer than itself.

And as for a Bridge on Uranus ….

As far as Helmuth was concerned, Jupiter was quite bad enough.

The beetle crept within sight of the end of the Bridge and stopped automatically. Helmuth set the vehicle’s “eyes” for highest penetration, and examined the nearby I-beams.