Galileo’s Dream. Kim Stanley Robinson

look for, rather than represent it to perfect scale, which in the diminution of the drawing simply made it too small. Paying attention was itself a kind of magnification.

      Drawing the constellations with their new host of companion stars was a different kind of problem, easier in some ways, as being mostly a schematic, but much harder too, in that there was no chance of representing what the view through the glass actually looked like. He altered sizes far beyond what he saw, to give an impression of the different brightnesses; but using black on white to represent white on black would never be satisfactory. White marks on black, as in an etching, would be better.

      He drew till his fingers got too cold. He made fair copies in the mornings, exaggerating to make the impressions bolder than ever. He made ink washes, very delicate; also bold schematics that would serve as guides to an engraver, because already he had plans for a book to accompany the spyglasses, just as an instruction manual had accompanied his military compass. Although here it really came down to seeing for oneself. The Milky Way, for instance; he could see that it was composed of a vast number of stars granulated together, a truly astonishing finding; but there was no way at all to draw that. People would have to see for themselves.

      He fell deeply into his new routine. He had always been an insomniac, and now there was a useful way to spend those sleepless hours. He simply did not go to bed, but stayed out on the terrace by the occhialino, looking through it and jotting down notes, comfortable in the solitary silence of the sleeping town. He had not known how much he enjoyed being alone. He wrote up what he had observed at dawn, and then slept through many a bright cool morning, wrapped in a blanket against a sunny wall in the corner, under the gnomon of the house’s big L.

      With the shorter days of November came winter, and clouds. On those nights he read, or caught up on his sleep, if he could; but on many a night he woke every hour or two, his brain full of stars, and went out to check the sky. If it had cleared he would stir the coals of the kitchen fire and put a pot of mulled wine on the grate, add a few sticks and go out to set up the glass, feeling that swirl of dust in the blood that he loved so much. He was on the hunt all right! And never had he had such a quarry! Nothing could keep him from looking when the night was clear. If his work in the daytime had to suffer-and it did-so be it. Those bastard pregadi didn’t deserve his work anyway.

      He had ordered one of the work tables moved onto the terrace, placed under a table umbrella, next to a couch. He had a lantern that could be shuttered, and workbooks, inkpots, quills; and three spyglasses on tripods, each with different powers and occlusions. Lastly, blankets to throw over his shoulders. Mazzoleni and the cook kept the household running in the mornings while he slept, and stocked the supplies for his nighttime needs; both were the kind of person who falls asleep at sunset, so they didn’t see him at work unless he forced them to. After a while, he never did; he liked being by himself through the frosty nights, looking at first one thing and then another.

      On the night of 7th January, 1610, he was out looking at the planets. As he had written in a letter he was composing for young Antonio Medici, The planets are seen very rotund, like little full moons, and of a roundness bounded and without rays. But the fixed stars do not appear so; rather they are seen fulgurous and trembling, much more with the glass than without, and so irradiated that what shape they possess is not revealed.

      So the planets, being obvious little disks, were interesting. And Jupiter was now in the west after sunset. It was the biggest of the planets in the glass, no surprise to anyone used to the way it dominated the night sky whenever it was visible.

      Galileo got it in the middle of the eyepiece, and then saw that there were three bright stars to left and right of it, aligned with it in the plane of the ecliptic. He marked their positions on a new sheet of his letter to Antonio, and looked at them for a long time. They did not twinkle like the stars, but gleamed steadily. They were almost perfectly in a line with each other. They were almost as bright as Jupiter, or even brighter, although smaller. Jupiter itself was a very distinct disc.

      The next night he looked at Jupiter again, and was shocked to find that the three stars were still there, but this time all to the west of the great planet, whereas on the previous night two of them had been to its east. He wondered if the ephemerides was wrong about Jupiter’s current movement.

      On 9th January it was cloudy, and nothing could be seen. But the night of the tenth was clear again.

      This time only two of the bright stars were there, both to the east of Jupiter. One was slightly less bright than the other, though on the previous nights they had all been the same.

      Mystified, intrigued to the point of obsession, Galileo started a new sheet in his workbook, and copied there the diagrams he had already written in at the end of the letter to Antonio. The letter itself he put aside, as being premature.

      In his new desire for night, the days themselves passed slowly, and he did the necessary work without paying the slightest attention to it, as if dreaming on his feet. This was a sign, wellrecognized by the household: he was on the hunt. And just as they never woke sleepwalkers for fear of damaging their sanity, they left him alone at these times, and kept the boys quiet and the students at bay, and put food in him almost as if spoon-feeding a baby. Of course it was true he would beat them if they distracted him, but they enjoyed the craft of it too.

      On the night of 12th January, Galileo trained the glass on Jupiter in the last moments of twilight. At first he could see again only two of the little bright stars; but an hour later when it was fully dark he checked again, and one more had become visible, very close to Jupiter’s eastern side.

      He drew arrows trying to clarify to himself how they were moving, shifting his attention between the view through the glass and his sketches on the page. Suddenly it became clear, there in the reiterated sketches: the four stars were moving around Jupiter, orbiting it in the same way the moon orbited the Earth. He was seeing circular orbits edge-on; they lay nearly in a single plane, which was also very close to the plane of the ecliptic, in which the planets themselves moved.

      He felt the ringing in him. He straightened up, blinking away the tears in his eyes that always came from looking too long, and that this time came also from the sudden surge of an emotion he couldn’t give a name to, a kind of joy that was also shot with fear. ‘Ah,’ he said. A touch of the sacred, right on the back of his neck: God had tapped him. He was ringing.

      No one had ever seen this before. People had seen the moon, had seen the stars; they had never seen this. I primi al mondo! The first man to see Jupiter’s four moons, which had been circling it since the creation.

      Everything he had seen over the last week fell into place. He stood, staggering a little under the impact of the idea, and circled the work table as if imitating a moon. When there had been only two dots, the others could have been behind the big planet-or before it. And he saw also that the orbiting moon now outermost could perhaps have moved so far away from Jupiter as to be outside his eyepiece’s little circle. The shifts in position suggested they were moving fairly quickly. Earth’s moon took only twentyeight and a half days for its orbit. These four seemed faster still, and perhaps could be moving at differing speeds, just as the planets moved at differing speeds in the sky.

      If he was right, then he could expect to see several more things. Seeing the orbits side-on, the moons would appear to slow down as they approached their maximum distance from Jupiter, and be fastest when right next to it. They would also disappear when behind it (or before it) in a regular pattern, and always reappear on the other side, never on the same side. Repeated observations should make it possible to sort out which moon was which, and determine which orbited closest to Jupiter and which farthest away. Knowing that would help him to calculate each orbital period, and that would allow him to keep steady track of them, and even predict where they would be, in a Jovian ephemerides of his own devise.

      ‘My God,’ he said, overwhelmed at these thoughts, suddenly weeping, feeling he should fall to his knees to say a prayer in thanks to God, only his knees were too stiff, he was too cold. Anyway it was looking through the glass that was the prayer. ‘I’m the first in the world!’

      Which-when he recovered from the awe of it-really should be something he could turn