Pam coded it and sent it to Earth. And presently, on Earth, astronomers looked at each other helplessly. Because Keller had stated the only possible explanation. Objects like real suns, if so close together, would tear each other to bits and fuse in flaming novas. Moreover, the pattern of motion of the red-spark-producing objects could not have come into being of itself. It was artificial. There was a group of Things in motion toward Earth's solar system. They would arrive within so many days. They were millions of miles apart, but their gravity-fields were so strong that they orbited each other within hours. If they had gravity-fields, they had mass, which could be as artificial as their gravity. And, whirling about each other in the maddest of dances, ten suns passing through the human solar system could leave nothing but debris behind them. Oddly enough, the ships that made those gravity-fields might be so small as to be beyond the power of a telescope to detect at a few thousand miles. The destruction of all the solar planets and the sun itself might be accomplished by motes. They would not need to use power for destruction. Gravitation is not expended any more than magnetism, when something is attracted by it. The artificial gravity-fields would only need to be built up. They had been. Once created, they could exist forever without need for added power, just as the sun and planets do not expend power for their mutual attraction, and as the Earth parts with no energy to keep its moon a captive. The newspapers did not publish this news. But, very quietly, every civilized government on Earth got instructions for the making of a gravity-field detector. Most had them built. And then for the first time in human history there was an actual and desperately honest attempt to poll all human knowledge and all human resources for a common human end. For once, no eminent figure assumed the undignified pose involved in standing on one's dignity. For once, the public remained unworried and undisturbed while the heads of states aged visibly. Naturally some of the people in the secret frantically demanded that the five in the fortress solve the problem all the science of Earth could not even attack. Incredible lists of required information items went out to Burke and Keller and Holmes. Keller read the lists calmly and tried to answer the questions that seemed to make sense. Holmes doggedly spent all his time experiencing cubes in the hope that by sheer accident he might come upon something useful. Pam, scowling, coded and decoded without pause. And Sandy looked anxiously at Burke. "I'm going to ask you to do something for me," she said. "When we went down to the Lower Levels, I thought I saw something moving. Something alive." "Nerves," said Burke. "There couldn't be anything alive in this place. Not after so many years without air."