No doubt, thought Lucky, if he placed himself in the proper position he would find himself staring into the reflection of the Sun. He became aware that the plate was changing its angle of elevation, becoming less horizontal, more vertical. He looked away to see if it were shifting in such a way as to catch the Sun.
When he looked back he was amazed. The clear square was no longer clear. Instead, it was a dull black, so dull that not all the light of Mercury's Sun seemed to be able to brighten it.
Then, as he watched, that dullness trembled, broke, and fragmented.
It was bright again.
He watched it through three more cycles as the angle of elevation made it more and more vertical. First, incredible reflection; then, complete dullness. During the dullness, Lucky realized, light would be absorbed; during the glossiness, it would be reflected. The alternation in phase might be perfectly regular, or there might be a deliberate, irregular pattern. He could not linger to find out and, if he did, it was doubtful whether his knowledge of hyperoptics would be enough to enable him to understand the purpose of it all.
Presumably hundreds or even thousands of such squares, all connected by a network of cables and all powered from an atomic micropile inside the Dome, were absorbing and reflecting light in a set way at different angles to the Sun. Presumably, this, in some way, could force light energy through hyperspace in a controlled manner.
And, presumably, torn cables and smashed plates prevented the over-all pattern from being properly completed.
Lucky tried his ergometer again. It was much brighter now, and again he followed in the indicated direction.
Brighter, brighter! Whatever it was he was following, it was something that was changing its position. The source of gamma rays was not a fixed point on Mercury's surface.
And that meant it was not merely an outcropping of radioactive ore. It was something portable, and to Lucky that meant it was man or something belonging to man.
Lucky saw the figure first as a moving speck, black against the fire-lit ground. The sight came after a long spell in the open Sun, at a time when he had been about to find himself a shadow in which to let the slowly accumulating heat drain away.
Instead, he accelerated his pace now. He estimated the temperature outside his suit to be at not quite the boiling point of water. Inside, fortunately, it was considerably lower.
He thought grimly: If the Sun were overhead and not at the horizon, even these suits would be of no use.
The figure paid no attention to him. It continued on its own path, its gait showing it far from as expert in handling low gravity as was Lucky. Indeed its motion might almost be described as lumbering. Yet it managed to devour space. It covered the ground.
It wore no inso-suit. Even at long distance, the surface exposed to Lucky's gaze was obviously one of metal.
Lucky paused briefly in the shade of a rock but forced himself into the open again before there was time for much cooling.
The figure seemed unbothered by the heat. At least, in the time Lucky watched him he made no move to enter shadows, though, he passed within a few feet of some.
Lucky nodded thoughtfully. It all fit well. He sped on. The heat was beginning to feel like something he could touch and squeeze. But it would only be a few moments now.
He had abandoned his low-slung lope now. Every bit of his muscular power was being put into giant strides of up to fifteen feet each.
He shouted, "You! You there! Turn around!" He said it peremptorily, with all the authority he could produce, hoping that the other could receive Ms radio signal and that he would not be reduced to sign language.
Slowly the figure turned, and Ducky's nostrils flared in a kind of cold satisfaction. So far, at least, it was as he thought, for the figure was no man-nothing human at all!
11. Saboteur!
The figure was tall, taller even than Lucky. It was nearly seven feet tall, in fact, and broad in proportion. All of the figure that met the eye was gleaming metal, brilliant where it caught the Sun's rays, black with shadow where it did not.
But underneath that metal was no flesh and blood, only more metal, gears, tubes, a micropile which powered the figure with nuclear energy and produced the gamma rays that Lucky had detected with his pocket ergometer.
The limbs of the creature were monstrous and its legs were straddled far apart as it stood there facing Lucky. What passed for its eyes were two photoelectric cells that gleamed a deep red. Its mouth was a slash across the metal on the lower part of its face.
It was a mechanical man, a robot, and it took Lucky no more than one glance to know that it was no robot of Earth's manufacture. Earth had invented the posi-tronic robot, but it had never built any model like this.
The robot's mouth opened and closed in irregular movements as though it were speaking.
Lucky said, "I cannot hear sound in a vacuum, robot." He said it sternly, knowing that it was essential to establish himself as a man and therefore a master at once. "Switch to radio."
And now the robot's mouth remained motionless but a voice sounded in Lucky's receiver, harsh and uneven, with the words unnaturally spaced. It said, "What is your business, sir? Why are you here?"
"Do not question me," said Lucky. "Why are you here?"
A robot could only be truthful. It said, "I have been instructed to destroy certain objects at intervals."
"By whom?"
"I have been instructed not to answer that question."
"Are you of Sirian manufacture?"
"I was constructed on one of the planets of the Sirian Confederation."
Lucky frowned. The creature's voice was quite unpleasant. The few robots of Earth manufacture that Lucky had had occasion to see in experimental laboratories had been outfitted with voices boxes which, by direct sound or by radio, seemed as pleasant and natural as a well-cultivated human voice. Surely the Sirians would have improved on that.
Lucky's mind shifted to a more immediate problem. He said, "I must find a shadowed area. Come with me."
The robot said at once, "I will direct you to the nearest shade." It set off at a trot, its metal legs moving with a certain irregularity.
Lucky followed the creature. He needed no direction to reach the shade, but he lagged behind to watch the robot's gait.
What had seemed to Lucky, from a distance, to be a lumbering or a clumsy pace, turned out, at close hand, to be a pronounced limp. A limp and a harsh voice. Two imperfections in this robot whose outer appearance was that of a magnificent mechanical marvel.
It struck him forcibly that the robot might not be adjusted to the heat and radiation of Mercury. Exposure had damaged it, probably. Lucky was scientist enough to feel a twinge of regret at that. It was too beautiful to have to endure such damage.
He regarded the machine with admiration. Underneath that massive skull of chrome-steel was a delicate ovoid of sponge platinum-indium about the size of a human brain. Within it, quadrillions of quadrillions of positrons came into being and vanished in millionths of a second. As they came into being and vanished they traced precalculated paths which duplicated, in a simplified way, the thinking cells of the human brain.
Engineers had calculated out those positronic paths to suit humanity, and into them they had designed the "Three Laws of Robotics."
The First Law was that a robot could not harm a human being or let one come to harm. Nothing came ahead of that. Nothing could substitute for it.
The Second Law was that a robot must obey orders except those that would break the First Law.
The Third Law allowed a robot to protect itself, provided the First and Second Laws weren't broken.
Lucky came out of his short reverie when the robot stumbled and almost fell. There was no unevenness in the ground that Lucky could see, no trifling ridge that might have caught his toe. If there had been, a line of black shadow would have revealed it.