Steel just gaped in awe, believing anything possible of him. Chimal began to spin the bucket in a small circle, faster and faster, lifting it at the same time, until it was swinging in a circle straight up into the air, upside down at the summit of its loop… The water stayed in; not a drop was spilled. Then, slowly, he decreased the speed, until the container was once again on the floor.

“Now, one more question,” he said, picking up a book. “If I were to open my hand and let go of this book — what would happen?”

“It would fall to the floor,” she told him, intensely proud to have answered so many questions correctly.

“Right again. Now follow closely. The force that pulls the book to the floor and one that holds the water in the bucket is the same force, and its name is centrifugal force. There is another force on large planets called gravity that seems to act the same way, though I do not understand it. The important thing to remember is that centrifugal force also holds us down, so we don’t fly up into the air, and is also the reason why we could walk across the sky and look up at the valley over our heads.”

“I don’t understand any of that,” she admitted.

“It’s simple. Say that instead of a cord I had a spinning wheel. If the container were hung from the rim of the wheel the water would stay inside of it just as it did when I spun it on the cord. And I could fasten two containers to the wheel, opposite each other, and the water would stay in each one. The bottom of each container would be down for the water it held — yet the direction down would be directly opposite for each of them. The same thing is true for us, because this world of rock is spinning too. So down in the village is below your feet — and down on the sky is toward the sky. Do you follow all of this?”

“Yes,” she told him, although she did not, but she wanted to please ham.

“Good. Now the next step is the important one and I want you to be sure you are with me. If down is below your feet in the village and down is toward the sky when you are opposite it, then halfway between them the force must be equal, so that there is no force acting at all. If we could get halfway to the sky from the village we could just float there.”

“That would be very hard to do, unless you were a bird. And even birds are prevented from leaving the valley by a certain device of which I have heard.”

“Very true. We can’t climb up through the air, but we can go through a tunnel in the rock. The valley is in an opening in the rock, but it is solid at both ends. If there is a tunnel leading to the spot, it’s called the axis of rotation, that’s the name from the book, we could go there and float in the air.”

“I don’t think I would like that.”

“I would. And I have found the right tunnel on the charts. Will you go with me?”

Watchman Steel hesitated; she had no desire to experience adventures of this land. But the First Arriver’s wishes must be treated as law.

“Yes, I will come.”

“Good. We’ll go now.” The books were satisfactory and he enjoyed his studies, but he needed human contact too. In the village people were always together. Watchman Steel was the first person he had met here, and they had snared experiences together. She was not bright, but she tried to please. He put some food concentrates and a water bottle into his belt pouch: he had taken to wearing this as did all the others. It held the communicator, his writing instruments, some small tools.

“It’s the second stairway past the refectory,” he told her as they left.

At the foot of the stairway they stopped while she set her eskoskeleton for climb. It moved one foot after the other, providing all the power to lift her weight and therefore prevented undue strain on her heart. Chimal slowed down to match her mechanical pace. They went up seven levels before the stairway ended.

“This is the top level,” Steel said as she reset the controls. “I have only been up here once before. There are just storerooms here.”

“More than that, if the diagrams are correct.” They walked the length of the corridor, past the last doorway, and on through the drill-scored, chill rock. There was no heated flooring here, but their boots did have thick, insulated soles. At the very end, facing them, was a metal doorway with the painted legend in large, red letters: OBSERVERS ONLY.

“I can’t go in there,” she said.

“You can if I tell you to. In the observer’s breviary it states that watchmen or anyone else may be ordered by observers into any area to do what is needed.” He had never read anything of the sort, but she did not have to know that

“Of course, then I can go with you. Do you know the combination of this lock?” She pointed at the complex dial lock that was fastened to the edge of the door on a hasp.

“No, there was nothing about there being a lock on this door.”

This was the first sealed door that he had seen. Rule and order were enough to keep the Watchers from entering where they were not wanted. He looked closely at the lock, and at the hasp.

“This has been added after the original construction,” he said, pointing to the screw heads. “Someone has drilled into the metal frame and door and attached this.” He took out a screwdriver and twisted a screw loose. “And not a very good job either. They did not fix it very securely.”

It took only a few moments to remove the retaining screws and put the lock, still sealed to the hasp, onto the tunnel floor. The door opened easily then, into a small, metal-walled room.

“What can this mean?” Steel asked, following him in.

“I’m not sure I know. There were no details on the charts. But — we can follow the instructions and see what happens.” He pointed to the lettered card on one wall. “One, close door, that’s simple enough. Two, hold fast to handgrips.”

There were metal loops fixed to the walls at waist height, and they both took hold of them.

“Three, turn pointer in proper direction.”

A metal arrow beneath the sign had its tip touching the word DOWN. It was pivoted on its base and Chimal released one hand to push the point of the arrow to UP. When he did so a distant humming began and the car began to move slowly upward.

“Very good,” he said. “Saves us a long climb. This car must be fixed in a vertical shaft and is pulled up and down by a device of some kind. What’s the matter?”

“I… I don’t know,” Steel gasped, clutching to the ring with both hands. “I feel so strange, different.”

“Yes, you’re right. Lighter perhaps!” He laughed and jumped up from the floor, and it seemed to take longer than usual before he dropped back. “The centrifugal force is decreasing. Soon it will be gone completely.” Steel, not as enthused by the idea as he was, clasped tight and pressed her head to the wall with her eyes closed.

The trip was relatively brief, and, when the car stopped, Chimal pushed up on his toes and floated free of the floor.

“It’s true — there is no force acting. We are at the axis of rotation.” Steel curled over, gasping and retching, trying to control the spasms in her stomach. The door opened automatically and they looked along a circular corridor with rods, like raised rails, running the length of it. There was no up or down and even Chimal felt a little queasy when he tried to imagine in what direction they were facing.

“Come on. We just float, then pull ourselves along those rods to wherever the tunnel goes. It should be easy.” When the girl showed no intention of moving he pried her hands loose and gently pushed her into the end of the tube, knocking himself back against the wall at the same time. She screamed faintly and thrashed about, trying to clutch onto something. He launched himself after her and discovered it was not easy at all.

In the end he found that the surest way to progress was to pull forward lightly, then guide himself by sliding his hands along the bar as he went. Watchman Steel, after emptying her stomach felt somewhat better and managed to follow his instructions. Bit by bit they progressed the length of the tube to the doorway at the end, then let themselves through into a spherical room that looked out onto the stars.