The Mote in God's Eye

New crew and old hands swarmed around the ship, yanking out damaged equipment and hurriedly thrusting in spares from Brigit’s supply depot, running checkout procedures and rushing to the next job. Other replacement parts were stored as they arrived. Later they could be used to replace Sinclair’s melted-looking jury rigs… if anyone could figure out how. It was difficult enough telling what was inside one of those standardized black boxes. Rod spotted a microwave heater and routed it to the wardroom; Cargill would like that.

When the fueling was nearly finished, Rod donned his pressure suit and went outside. His inspection wasn’t needed, but it helped crew morale to know that the Old Man was looking over everyone’s shoulder. While he was out there, Rod looked for the intruder.

The Face of God stared at him across space.

The Coal Sack was a nebular mass of dust and gas, small as such things go—twenty-four to thirty light years thick—but dense, and close enough to New Caledonia to block off a quarter of the sky. Earth and the Imperial Capital, Sparta, were forever invisible on its other side. The spreading blackness hid most of the Empire, but it made a fine velvet backdrop for two close, brilliant stars.

Even without that backdrop, Murcheson’s Eye was the brightest star in the sky—a great red giant thirty-five light years distant. The white fleck at one edge was a yellow dwarf companion star, smaller and dimmer and less interesting: the Mote. Here the Coal Sack had the shape of a hooded man, head and shoulders; and the off-centered red supergiant became a watchful, malevolent eye.

The Face of God. It was a famous sight throughout the Empire, this extraordinary view of the Coal Sack from New Cal. But standing here in the cold of space it was different. In a picture it looked like the Coal Sack. Here it was real.

And something he couldn’t see was coming at him out of the Mote in God’s Eye.

6. The Light Sail

One gravity only—with queasy sensations as MacArthur lined up on her proper interception course. Elastic webbing held him in the acceleration chair during these few moments of changing but normal gravity—minutes, Rod suspected, that he’d soon look back on with wistful longing.

Kevin Renner had been mate of an interstellar trading vessel before joining MacArthur as her sailing master. He was a lean man with a narrow face, and he was ten years older than Blaine. As Rod steered his acceleration chair up behind him, Renner was matching curves in a view screen; and his self-satisfied grin was not the expression of a Navy man.

“Got our course, Lieutenant Renner?”

“Yes, sir,” Kevin Renner said with relish. “Right into the sun at four gees!”

Blaine gave in to the desire to call his bluff. “Move her.”

The warning alarms sounded and MacArthur accelerated. Crew and passengers felt their weight settle gradually deeper into beds and chairs and couches, and they nerved themselves for several days of weighing far too much.

“You were joking, weren’t you?” Blaine asked.

The Sailing Master looked at him quizzically. “You knew we were dealing with a light-sail propulsion system, sir?”

“Naturally.”

“Then look here.” Renner’s nimble fingers made a green curve on the view screen, a parabola rising sharply at the right. “Sunlight per square centimeter falling on a light-sail decreases as the square of the distance from the star. Acceleration varies directly as the sunlight reflected from the sail.”

“Of course, Mr. Renner. Make your point.”

Renner made another parabola, very like the first, but in blue. “The stellar wind can also propel a light sail. Thrust varies about the same way. The important difference is that the stellar wind is atomic nuclei. They stick where they hit the sail. The momentum is transferred directly—and it’s all radial to the sun.”

“You can’t tack against it,” Blaine realized suddenly. “You can tack against the light by tilting the sail, but the stellar wind always thrusts you straight away from the sun.”

“Right. So, Captain, suppose you were coming into a system at 7 percent of the speed of light, God forbid, and you wanted to stop. What would you do?”

“Drop all the weight I could,” Blaine mused. “Hmm. I don’t see how it’d be a problem. They must have launched the same way.”

“I don’t think they did. They’re moving too fast. But pass that for a minute. What counts is they’re moving too fast to stop unless they get very close to the sun, very close indeed. The intruder is in fact diving right into the sun. Probably it will tack hard after the sunlight has decelerated it enough… provided the vessel hasn’t melted and the shrouds haven’t parted or the sail ripped. But it is such a close thing that they simply have to skydive; they have no choice.”

“Ah,” said Blaine.

“One need hardly mention,” Renner added, “that when we match course with them, we too will be moving straight toward the sun…

“At 7 percent of the speed of light?”