McAndrew said, “Then where is it? We have no other lead.”
“It went with him.” I was surprised that the two of them were slow to catch on. “If it gives the practical details it’s worth an enormous fortune. He didn’t want to risk anyone else getting their hands on it.”
“We have to find it, and him.” McAndrew sounded unusually forceful. He saw my expression. “Oh, not the inventions, Jeanie. You know I don’t give a damn about them. We need the theory.”
Mary McAndrew turned to me. “I told you. He hasn’t changed a bit. He needs a keeper.”
I asked, “But where did he go?”
McAndrew snapped at us. “If the pair of you would stop blathering, maybe we’d have a chance to find out.”
Heinrich Grunewald was still talking. Mac reversed the video to the point where his father was hefting the blue book.
“… developments can be found here.” Grunewald flourished the notebook in a self-satisfied way and finally placed it back out of sight. “With industrial sabotage so common, I do not wish to perform my final validation experiments where others might find a way to steal or even to interfere.”
Mary McAndrew said, “Och, he’s crazy suspicious. He was always paranoid. I’ve never known another man look under every bed before he’d get in it, no matter who he was with and what he had to look forward to.”
McAndrew and I both shushed her, as Grunewald went on, “So to do the validation I’m taking the Fafner out, away from the main shipping lanes—”
“Got him,” I said.
“Keep quiet,” McAndrew snapped. But I’m a seasoned cargo captain, and for a change I knew something he didn’t. It didn’t matter whether or not Heinrich Grunewald told us anything else. If he had taken his ship out, as he said, then his flight plan would be on file. So would any firing of the ship’s engines.
The man was gone, but not forgotten and not untraceable. It might take a while, but I felt sure we would be able to track down McAndrew’s long-lost father.
Like many things in life, the problem I had been so sure I could solve proved more difficult than it sounded.
We headed for the Penrose Institute to perform the calculations. Mary McAndrew told us that she could not come, she had to pay some attention to “poor neglected Fazool.” But I was to let her know what we found.
“I know he’s surely dead,” she said to me as we left for Equatorport. “He was a wicked, obstinate, reckless man. But the two of us had some great times, and I was awful fond of Heinrich. Why, I was even faithful to him.”
It would have been unkind to ask for how long.
Mac and I headed for the Institute, and at first everything went according to plan. I delved into the old data bases and found the flight plan of the Fafner. Among the listed on-board equipment, tantalizingly, the manifest included the enigmatic item, “strong field modifier, prototype.”
I learned the exact second of the ship’s departure. I found its nominal destination, though that could change through subsequent course corrections or changes of mind. I obtained a complete list of subsequent engine firings, which even without the record sent back from the Fafner’s inertial navigation system would allow us to pinpoint the ship’s last known location. After all the engine firings, a certain stochastic element affected the Fafner’s movements depending on the vagaries of gravitational perturbation by small bodies and variations in solar wind. But natural body positions for anything substantial were in the data banks on an hour-by-hour basis, and the programs to compensate for their effects were routine.
The calculations took a while, even with McAndrew’s talent for instant shortcuts. Once we had answers we borrowed the synthetic aperture distributed observation system for a few days and surveyed the sky sector where the Fafner should be found.
Result: nothing. Not a sign. No Fafner, not in the region we had defined as most probable or in one ten times as big in all directions. The ship had disappeared.
I checked the calculations, redoing everything the long way. The Fafner was not a big ship, nothing to compare with a cargo carrier or even a large passenger vessel, but it was thirty meters long and almost fifteen across. Anything that size would stand out prominently on the observations made by the big scope, especially when you used a time exposure to sort out moving objects within the Solar System from the fixed celestial background. Comparison with known natural bodies ought to do the rest.
I found nothing wrong with McAndrew’s calculations. He checked my checking. That took two more days. Finally we were ready to admit defeat. By this time a dozen others at the Institute were taking an interest. McAndrew phrased the dilemma for all of us. “Objects just can’t disappear. Here are the possibilities: The Fafner might have totally disintegrated. It might have hidden away inside another object. Or it might be deliberately covered with nonreflective material at the wavelengths used by the Institute scopes.”
“Or stolen away by aliens,” I added. I was tired.
McAndrew nodded as though that was a serious possibility. “In any case,” he said, “we’ve gone as far as we can just sitting and looking.”
“The ship can’t be far away from where we calculated,” I said. I could see where the discussion was heading, and I knew that we faced a very tough job. “It’s in the Inner System, and near the plane of the ecliptic. In the Asteroid Belt, almost certainly.”
McAndrew nodded and looked gloomy. “Aye. Wouldn’t you just know it’d be that way?”
The others muttered vague expressions of sympathy.
To see why, imagine that you are asked to look for something small. Would you rather search a large volume or a small one?
The answer to that question depends where you are and what you are seeking. The region of the Solar System that includes the Sun, planets, moons, asteroids, and the odd collection of misfit bodies forming the Edgeworth-Kuiper Belt is a substantial volume; it is shaped like a flat pillbox, about thirty billion kilometers across and maybe forty million deep. Say, a billion billion cubic kilometers of volume altogether. But that’s infinitesimal compared with the space bounded by the inner edge of the Oort cloud. There, we are talking a spherical region with a radius of a twentieth of a light-year. The volume in cubic kilometers is a number with thirty-five zeroes, too many for me to be comfortable with. You can subtract the volume of the pillbox, and it makes no noticeable difference.
The odd thing, though, is that inside the pillbox it’s much harder to find something. And if you had to pick one place where the search is more difficult than any other, the Inner Belt of the asteroids is where you’d least like to be.
The key word is clutter. There are far too many natural bodies in orbit. The Asteroid Belt contains everything from substantial bodies like Ceres, seven hundred and fifty kilometers across, all the way down to house-sized boulders, pebbles, and grains of sand. One good rule of thumb is that for every object of a given size, there will be ten times as many one-third that size.
The data bases at the Institute keep dynamic track of every body of any size, down to ten meters across. The Fafner was much bigger than that, so it ought to have been picked up in our search. Recognize that it hadn’t been, and where does that leave you? You know there are countless millions of objects near where the missing ship ought to be, and you have no idea at all why your original search failed.
So we would fly out there and take a look for ourselves, and hope that our human brains could spot an anomaly able to fool the smartest computers in the Solar System.