“How about their power plants?” asked Barlennan, determined to learn the worst now that he had started. “Aren’t there other radiations than light given off in nuclear reactions?” By the time this question reached the station Tebbetts had left, according to his promise; fortunately Benj was able to supply the answer. The information happened to be basic to the Project, which had been carefully explained to him right after his arrival. “The fusion converters give off neutrinos which we can detect, but we can’t spot their source exactly,” he told the commander. “That’s what the shadow satellites are for. They detect neutrinos, which are practically all coming from the sun. The power plants on Dhrawn and up here don’t count for much against that, even if it isn’t much of a sun. The computers keep track of where the satellites are and especially whether the planet is between a given one and the sun, so there’s a measure of the neutrino absorption through different parts of the planet. In a few years we hope to have a statistical X ray of Dhrawn. Maybe that isn’t a good analogy for you: I mean a good idea of the density and composition of the planet’s insides. They’re still arguing, you know, whether Dhrawn should be called a planet or a star or whether the extra heat is from hydrogen fusion in the middle or radioactivity near the surface. “But I’m sure as can be that they couldn’t find your missing fliers from their neutrino emission, even if their converters are still on.” Barlennan managed to conceal his glee at this news; he merely answered, “Thanks. We can’t have everything. I take it you’ll tell me when your astronomer finds anything, or when he is sure he’ll find nothing; I’d like to know if I have to stop counting on that. I’m through talking for now, Benj, but call here if anything comes up on either the fliers or those friends of yours. After all, I’m concerned about them, though perhaps not the way you are about Beetchermarlf. Takoorch is the one I remember.” Barlennan, having had more direct contact with human beings and more selfish reasons to develop such skills, had been able to read more accurately between the lines of Benj’s talk and obtain a more nearly correct picture of the boy’s feelings than Dondragmer had. It would, he was sure, be useful; but he put it from his mind as he turned away from the communicator. “That could be both better and worse,” he remarked to the two scientists. “It’s certainly just as well we didn’t set up that blinker system for night communication; they’d have seen us certainly.”