housing was snagging on the roof. He worked the valve to feed just enough
additional hydrogen into the bag to provide the necessary buoyancy. Hydrogen:
there had been a year when this gas was banned in favor of inert helium. But
hydrogen had greater buoyancy, and was easier to prepare-after all, most of
the universe consisted of it!-and the fire hazard had been abated by making
the system self-contained, with no leakage of gas to the atmosphere. Of course
the abolition of tobacco smoking helped; today the average citizen was not an
incendiary mechanism. Therefore blowups should be few.
When precise balance had been obtained and he hovered inches off the roof,
he valved it down, cast loose the mooring and set off downwind.
It was, in its fashion, fun. He was floating, but not in free-fall. The
effect was quite different from space travel, and somewhat eerie. For one
thing, he was appallingly close to the planet. Fifty feet. Ahead of him a tall
building loomed; the wind should carry him by it, not through it, but he
didn't care to gamble. In space nothing changed direction of its own accord,
so his reflexes urged action. He used his armvanes to guide to the side.
Nothing happened. He was drifting in air, and had no purchase. Hastily he
pedaled. The fan pushed against the atmosphere, increasing his forward
velocity. Now the vanes had some slight traction, and he wobbled over to the
side, barely clearing the building.
"Birth!" a woman screamed irritably as the blimp almost sideswiped her
window vegetable garden. "Get in your lane, purebred!"
Embarrassed, Shetland guided his craft into the airway he now discerned,
marked off by a pattern of buoys anchored to buildings and utility poles.
Faster blimps traveled higher, and traffic bore to the right. The street was
east-west, not quite aligned with the wind, so he had to pedal and steer
vigorously.
"Birth," he murmured, remembering the woman's curse-word. So reproduction
itself had become anathema in some circles. "Purebred." That was a more
established insult, more specific. He did not care to explain that he had been
born before the law had changed. But this sort of language was all too typical
of what he disliked on Earth; in space there was no parallel.
Below him were the massed cycles that Sosthenna, her of the shade of gray,
had warned him about. There were thousands of them. Most were two-wheeled, but
quite a number were one- or three- or four-wheeled: unicycles, tricycles,
quadricycles. The last were actually pedalcars, some loaded with families,
some even with solar collectors covering them. There were no fuel-powered
vehicles at all.
No mystery about that. The energy-exorbitant last century had virtually
depleted all ready sources of power. The developing crisis had been apparent
for half a century or more, but nothing had been done until too late. The
government of the world had finally reserved all remaining fossil fuel sources
for offplanet use, at one stroke abolishing the age of the automobile, jet
plane and powered watercraft. It had been desperation, not foresight.
Suddenly the pollution of the environment had decreased sharply, physical
exertion had increased, and lives had lengthened. Serendipity: perhaps the
loss of the use of fossil fuels had been a net benefit. Of course the average
citizen had not thought so, and the public transport system had been strained-
until its current had also been cut off, during his most recent tour.
Mad world! he thought. It seemed determined to do the right things for the
wrong reasons, even though the right reasons were apparent. Space was more
predictable and more reasonable. Or were those concepts redundant? Could there
be unpredictable reason, or unreasonable predictability? Well, perhaps.
Relativistic theory seemed very like the former, and as for the latter, he had
experienced an event once that in retrospect-no, no, blot that out; it was too
red, too-
"Watch where yer goin', prok!" a voice yelled in his ear.