From sheer boredom, Pirx began feeding figures into his computer and formulating equations to compute the probability of a collision. The result was a figure so large that the computer would have had to drop the last eighteen decimal places just to accommodate the number on its displays.

Besides, the sector was empty. No comet tails, no clouds of cosmic dust—nothing. Theoretically, the wreckage of an earlier ship might just as well have turned up here as anywhere else in the universe—but only after an inconceivable number of years. But if that were the case, surely Thomas and Wilmer would have sighted it—say, from a distance of 250 kilometers. Suppose it had approached from the side of the Sun; in that case, the meteoradar would have sounded the alarm a good thirty seconds before impact. And even if the pilot had slept through the alarm, the automatic control would have triggered the yaw maneuver, whereas a malfunction in the automatic yaw control was practically unheard of: it might happen once, but not twice in a row in the space of a few days.

All this a layman might have deduced, a layman who knew nothing of the hazards present aboard ship during a manned space flight—perils far greater than colliding with a meteorite or a decayed comet. A spacecraft, even one as small as an AMU, is made up of nearly 114,000 major parts—major in the sense that a malfunction in any one of them could have disastrous consequences. The minor parts number more than a million. But even assuming a fatal accident, a spaceship would not simply disintegrate into ether—since, to cite an old spaceman’s adage, nothing is ever lost in space: toss out a cigarette lighter, and all you have to do is to plot its trajectory and be in the right place at the right time, and the lighter, following its own orbital path, will with astronomical precision plop into your hand at the designated second. The fact that in space a body will orbit about another to infinity means that sooner or later the wreckage of any spaceship is almost always bound to turn up. The Institute’s megacomputers had plotted more than forty million possible orbits in which the missing ships could be traveling, each of which was probed by concentrated pencils of the most powerful radar tracking equipment available on Earth. With the aforementioned results.