The door opened without a knock and Walt Franks entered. "Billing and cooing?" he asked. "Why do you two need an audience?" "We don't," answered Don. "This was business." "For want of evidence, I'll believe that. What's the dope?" "Walt, what are the chances of hooking up with the _Empress of Kolain_, which is en route from Mars to Venus?" "About equal to a celluloid snowball--you know where," said Franks, looking slyly at Arden. "Take off your coat, Walt. We've got a job." "You mean--Hey! Remind me to quit Saturday." "This is dead in earnest, Walt." Don told the electronics engineer all he knew. "Boy, this is a job that I wouldn't want my life to depend on. In the first place, we can't beam a transmitter at them if we can't see 'em. And in the second place, if we did, they couldn't receive us." "We can get a good idea of where they are and how they're going," said Channing. "That is common knowledge." "Astronomy is an exact science," chanted Franks. "But by the time we figure out just where the _Empress of Kolain_ is with respect to us at any given instant we'll all be old men with gray beards. She's crossing toward us on a skew curve--and we'll have to beam it past Sol. It won't be easy, Don. And then if we do find them, what do we do about it?" "Let's find them first and then work out a means of contacting them afterward." "Don," interrupted Arden, "what's so difficult?" Franks fell backward into a chair. Don turned to the girl and asked: "Are you kidding?" "No. I'm just ignorant. What is so hard about it. We shoot beams across a couple of hundred million miles like nothing and maintain communications at any cost. What should be so hard about contacting a ship?" "In the first place, we can see a planet, and they can see us, so they can hold their beams. A spaceship might be able to see us, but they couldn't hold a beam on us because of the side sway. We couldn't see them until they are right upon us and so we could not hope to hold a beam on them. Spaceships _might_ broadcast, but you have no idea what the square law of radiated power will do to a broadcast signal when millions upon millions of miles are counted in. A half million watts on any planet will not quite cover the planet as a service area on broadcast frequencies. On short waves it will because of the skip distance. But for square-law dissipation, you can't count skip distances--and in space it would be a case of the signal losing in strength according to the inverse square of the distance. So they don't try it. A spaceship may as well be on Rigel as far as contacting her in space goes. "We might beam a wide-dispersion affair at them," continued Channing. "But it would be pretty thin by the time it got there. And, having no equipment, they couldn't hear us." "May we amend that?" asked Franks. "They are equipped with radio. But the things are used only in landing operations where the distance is measured in miles, not Astronomical Units."