"Please make a complete check of every analyzer and telemetry circuit tonight, and we'll try again tomorrow. I want to think about this." * * * * * He thought about it, and he dreamed about it. And along about three o'clock in the morning he sat bolt upright in bed and stared at the dim moonlight on the opposite wall of the bedroom. It wasn't possible, he told himself audibly. It just wasn't possible! Mary stirred and leaned on one elbow beside him. "What's the matter. Are you having nightmares?" "Yeah--yeah, I guess I am. I'll be back in a minute, honey." He got up and padded to the door. "I've got to make a phone call." "At this time of night?" But Jim was gone. He turned on the hall light and dialed Sam's number. After a long time Sam answered sleepily. "Wake up!" said Jim. "I've just figured it out!" "Who the devil--? Oh, it's you, Jim. Figured out what? Do you know what time it is." "Do you know the results of your calibration re-check?" "How would I know that? I've got the night crew on it, but I didn't ask them to report to me in the middle of the night. Go back to bed, and let's talk about it in the morning." "They're not going to find anything wrong, Sam." "I could have told you that." "But the elements of the moon are different--and there's only one explanation." "What?" "Think about it a minute, Sam. We take a spectrograph of the sun, and we find the same elements that are here on earth. We turn it on Alpha Centauri and find the same thing. We turn it to the farthest stars we can find that give enough light to record by. Always the same. Calcium is calcium, whether it's on the earth or on a star a half billion light years away." "So?" Sam's voice was tired, and he sounded as if he was listening only because Jim was too good a friend to tell to go to hell for calling in the middle of the night. "So? So what?" Sam repeated. "So we go to the moon," said Jim, "and all of a sudden calcium isn't calcium, and the sodium on the moon isn't the same as the sodium on earth and on the sun and on Alpha Centauri and the stars a half billion light years away. Don't you see what that means!" "No, I guess not," said Sam dully. "Maybe in the morning--" "It means the moon just doesn't _belong_, Sam! It means the moon is completely foreign to anything in the Solar System, in the whole galaxy--in any galaxy we have been able to analyze. It means the moon has come from somewhere else, from a region of space where atoms and electrons are not even the same as atoms and electrons here. It must be a somewhere that's so far away it's beyond the edge of space as we know it!" "I'll get dressed and come over," said Sam. * * * * * Mary made chocolate and toast, and they sat around the kitchen table thinking and talking of the awesome implications of Jim's theory.