Chapter 19 Chapter 5 Passing Jupiter

Viewed through a telescope, Jupiter is majestic—a multicolored sphere that seems to fill the sky.Its size was tricky to grasp; Bowman had to keep reminding himself that it was eleven times the size of Earth, but for a long time that statistic didn't seem to matter much. Later, when he was explaining to himself using the tape from Hal's memory device, he discovered something that made him suddenly aware of Jupiter's incredible size. It was an illustration, the skin of the earth was peeled off, and it was nailed to the cross section of Jupiter like a piece of animal hide.Taking this as a background, the entire landmass on the earth is only as big as India on an ordinary globe.

Bowman adjusted the telescope on the "Discovery" to the maximum extent. At this time, he seemed to be hanging in the sky to observe a slightly flattened Earth. Form cloud rings.Sometimes these rings condensed into patches of colored vapor, each as large as a continent on the globe; sometimes they were connected by temporary bridges, each thousands of miles long.Under the cloud, there is more matter there than all the other planets in the solar system put together. "Besides that," Bowman wondered, "what else hangs over?" Above the swirling and roaring clouds that forever obscured Jupiter's true face sometimes floated round shadows.Here a Moon on Jupiter's near side passes beneath the distant Sun, its shadow sliding across the never-stationary Jupiter cloud cover.

There are also much smaller moons 20 million miles away from Jupiter.However, they are only flying peaks tens of miles in diameter, and spacecraft cannot fly near them.Every few minutes, the radar transmitter pumped out a silent electric thunderbolt at full force; the absence of echoes in the vacuum meant that no new satellites had appeared. What was received was the increasing intensity of the roar of radio waves from Jupiter itself.In 1955, on the eve of the dawn of the space age, astronomers were amazed to discover that Jupiter, despite millions of horsepower, emitted powerful radio waves in the decameter band.It's actually a blunt noise, accompanied by a halo of charged particles orbiting Jupiter, like Earth's Van Allen Belts (Van Allen belts: belts of high-intensity ionizing radiation surrounding the outer Earth's atmosphere, named after James Van Allen. ), but on a much larger scale.

Even though Discovery was traveling at 100,000 miles an hour, it would take almost two weeks to traverse the orbits of all of Jupiter's moons.There are more moons orbiting Jupiter than there are planets orbiting the sun; lunar observatories discover new moons of Jupiter every year, and the total now stands at thirty-six.The outermost moon, twenty-seven, was reversing on an unstable path nineteen million miles from its temporary owner.It's the prize in the never-ending tug-of-war between Jupiter and the sun, as Jupiter continually snatches short-lived worlds from the planetary belt, only to drop them at any time after millions of years.Only the inner satellites are its permanent possessions; the sun can never snatch them away.

Now, there is new prey between these two conflicting gravitational fields. "Discovery" is accelerating towards Jupiter along the complex orbit calculated by astronomers on Earth many months ago and constantly corrected by Hal.The jet manipulators are now and then automatically propelled in order to make fine corrections, but this is barely perceptible in the ship. Intelligence is constantly being sent back through radio contact with Earth.They were so far from home now that their signal would take fifty minutes to arrive, even at the speed of light. While the whole world was watching with concern, watching through their eyes and instruments as they approached Jupiter, it would take almost an hour for news of any of their discoveries to come back to Earth.

The telephoto cameras were constantly running as the spacecraft traversed the orbits of the giant inner moons.Those huge inner satellites are all larger than the moon, and all of them are unknown places. Three hours before the transit, the "Discovery" passed only 20,000 miles away from Europa; when the satellite was getting bigger and smaller, and it was rapidly moving towards the sun, all the instruments on the spacecraft were focused on it. . Seen from a distance, Europa looks like a big snowball, reflecting the brilliance of the distant sun with astonishing efficiency.Closer observations proved this to be the case; unlike the dark Moon, Europa was crystal white, and most of its surface was covered with glistening chunks like stranded icebergs.These chunks are almost certainly made of ammonia and water that Jupiter's gravitational field somehow failed to absorb.

Only along the equator are bare rocks to be seen; here is rugged no-man's land, full of canyons and boulders, encircling it in a black band.There are impact craters, but no signs of erupting volcanoes; Europa apparently never had an internal source of heat. As has long been known, there are traces of the atmosphere here.As the moon's dark edge streaks in front of the star, the star first dims briefly before total eclipse.And, in some areas, there are signs of clouds—perhaps droplets of condensed ammonia floating in the methane breeze. Europa suddenly appeared in the sky ahead and was quickly thrown behind the spacecraft; Jupiter was only two hours away at this time.Hal had carefully checked the orbit of the spacecraft again and again, and there was no need to make corrections in speed until the moment of closest approach.

Jupiter now filled the sky; it was too big for the eyes to see and the mind to conceive, so it had to be left alone.If it weren't for its brilliant colors—reds and pinks, yellows and oranges, even purples—Bowman might have thought he was flying above Earth's low cloud tops! Then, for the first time in their entire journey, they were about to lose sight of the sun.Although the sun has been fading and shrinking, it has been a frequent companion of Discovery in the five months since it left Earth.But Discovery's orbit is reaching into Jupiter's shadow, and it will soon fly behind the planet.

A thousand miles ahead, the twilight was approaching; behind, the sun was rapidly sinking into the clouds of Jupiter.The sunlight followed the horizon like two upside-down horns with flames, then gradually shrunk and disappeared in a flash of colorful fire.Night has fallen. The deeper they penetrated into Jupiter's night, the subterranean light gradually increased.Bowman once flew over northern Canada at the peak of an aurora display, when the frozen land was as desolate and as bright as this one.But the wilds of the Arctic - he reminded himself - were a hundred degrees warmer than the regions they were flying over now!

"Earth signal is fading rapidly," Hal announced. "We are entering the first refraction zone." They had expected this—in fact, it was one of the goals of their trip, since the absorption of radio waves would provide valuable intelligence about Jupiter's atmosphere.But now that they have turned to the far side of Jupiter and are now cut off from Earth, they can't help feeling suddenly unbearably alone.The radio outage lasted no more than an hour; then they would break out of Jupiter's eclipse and resume contact with humanity.However, this hour will be the longest they will feel in their lives.

Despite their youth, both Poole and Bowman were veterans of a dozen spaceflights--but now they both felt like rookies.They were trying for the first time; never before had any ship traveled at such a speed and dealt with such a strong gravitational field.At this critical moment, the slightest navigational error could send Discovery flying to the outermost edge of the solar system, never to be salvaged. Every minute passed slowly.Jupiter now stood ahead as a wall of phosphorescent will-o'-the-wisps, so high that the ship flew along the glowing wall.Although they knew that they were traveling so fast that even the gravity of Jupiter could not hold them back, it was difficult to imagine how the Discovery had not become a satellite of this monstrously large world. Finally, a dazzling light appeared on the distant horizon ahead.They came out of the shadows into the sun.At almost the same instant, Hal announced: "I have regained radio contact with Earth. I am pleased to report that the maneuvers have also been successfully completed. Our distance from Saturn is 167 days, 5 hours and 11 minutes." The calculations were off by less than a minute; the flyby was done without error.Like a billiard ball with the universe as its table, Discovery was powered by being ejected from the gravitational field of Jupiter in motion.It now goes thousands of miles per hour faster without using any fuel. However, this doesn't violate any laws of mechanics; nature always breaks even, and Jupiter just lost the momentum that Discovery gained.Jupiter slowed down—but, since Jupiter is 10.21 million times more massive than the spacecraft, its own orbital change was too small to be noticeable.The time when human beings can act on the solar system has not yet come. As the light came on, and the shrunken sun rose into the Jupiter sky, Poole and Bowman held each other's hands in silence. Although they could hardly believe it, the first part of the mission had been completed safely.