Charley Bren made another computation and said: "Well, Walt, we've been narrowing them down for quite a time now. We're getting closer and closer to them, according to the field intensity. I've just got a good idea of direction on that last five-minute shot. Have Franklen swivel us around on this course; pretty soon we'll be right in the middle of their shots." "We're approaching them asymptotically," observed Walt. "I wish I knew what our velocity was with respect to theirs. Something tells me that it would be much simpler if I knew." "Walt," asked Arden, "how close can you see a spaceship?" "You mean how far? Well, I don't know that it's ever been tried and recorded. But we can figure it out easy enough, by analogy. A period is about thirty thousandths of an inch in diameter, and visible from a distance of thirty inches. I mean visible with no doubt about it's being there. That's a thousand to one. Now, the _Solar Queen_ is about six hundred feet tall and about four hundred feet in its major diameter, so we can assume a little more than the four hundred feet--say five hundred feet average of circular area, say--follow me?" "Go on, you're vague, but normal." "Then at a thousand to one, that becomes five hundred thousand feet, and dividing by five thousand--round figures because it isn't important enough to use that two hundred and eighty feet over the five thousand--gives us one thousand miles. We should be able to see the _Solar Queen_ from a distance of a thousand miles." "Then at four thousand miles per second we'll be in and out of visual range in a half second?" "Oh no. They're rambling on a quite similar course at an unknown but high velocity. Our velocity with respect to theirs is what will determine how long they're within visual range." "Hey, Walt," came the voice of Charley Bren. "The intensity of Don's beam has been cut to about one quarter and is now continuous. Does that mean anything?" "Might mean trouble for them. Either they're running out of soup and mean for us to hurry up, or they assume we're close enough to obviate the need for high power. We'd better assume they want haste and act accordingly. How're the boys on the radio detectors coming along?" "Fine. They've taken over the direction finding and claim that we are right on their tail." "Anything in the sights, Jimmy?" "Not yet. But the electroscope boys claim that quarter power or not, the input is terrific." "Take a rest, Jimmy. We won't be there for a while yet. No use burning your eyes out trying to see 'em. There'll be time enough for you to do your share after we get 'em close enough to see with the naked eye. What do the beam-scanners say?"