Encounter With Tiber

by Buzz Aldrin

  After our rest days, the captain pushed acceleration back up to a comfortable eighty-eight percent of standard gravity, the same gravity we would experience on Setepos. We were already moving at just over ninety-eight percent of lightspeed, so we weren’t going to gain very much external-frame time by going faster. At such speeds, acceleration went almost entirely into mass—that is, because as a body approaches the speed of light it gets more massive, accelerating when we were already so close to lightspeed only added slightly to our speed but greatly increased the ship’s mass. Not that we felt any such thing on the ship, of course; relative to the inside of the ship, our mass was what it had always been. It was only an outside observer—if anyone could have observed us, far out in the dark between the stars, moving almost as fast as light—who would have seen our greater mass.

  But just as mass increased as we approached the speed of light, our internal time slowed down. Each tiny gain in velocity, bringing us a little closer to lightspeed, made time run much slower inside the ship. The trip was thus much shorter for us because we stayed under acceleration.

  When we had come out of high acceleration, one day of shiptime had equaled about six and a half days at home; now, as we approached peak velocity, one day of shiptime equaled eight days back home. The strangest thing, in some ways, was that there was no perception of this directly. It was not just the clocks, but our bodies, our heartbeats, the way we blinked, the motion of objects, so that there was nothing against which you could check time and see it running more slowly—nothing except a purely artificial device: the small clock in the cockpit that showed the date and time at home. That kept running faster, but for every other sign we had, the ship might as well have been on a routine training mission. We would go to bed, arise the standard seven-twentieths of a day afterward, and discover that three and three-fifths days had gone by at home. But even that clock did not actually register time at home; it simply displayed the results of a computer program that estimated it.

  The acceleration added to our comfort in another way; acceleration feels just like gravity, and gravity is handy stuff. It keeps food on the table, papers where you pile them, calcium in your bones, your body in bed at night, fluids in the tissues where they belong, and your food down. Our zero-point energy drive gave us so much surplus power, especially when hooked up to a small ship like Egalitarian Republic, that running the engines at eighty-eight percent of one gravity all the time was easier than spinning the ship, as the old Wahkopem Zomos had done decades before.

  The eightweeks flew by. It seemed to us that only a little over half a year passed, and yet the clock in the cockpit showed we had flown years into our future. There was so much to get done that there were times when I wished for less time compression; I wondered if we would ever have all the probes in order. In the last couple of days before we went into the tank again, I almost gave up sleeping and eating entirely.

  Captain Baegess noticed. “Assistant Thetakisus, you need a rest.”

  “I do, sir,” I agreed, “and I’ll sleep a lot in the tank. If the probes aren’t ready to fly—”

  “Then we’ll manage,” he said firmly. “How many do you have ready to go?”

  “All but eleven, sir, but four of those eleven are the rovers—”

  “Then get two rovers working. Tomorrow. After you get a full night’s sleep. That’s an order.”

  There wasn’t much to do about it, then, so I got the sleep, got back to work, and got the rovers working.

  Going back into the tank this time was, if anything, much worse. First of all we knew what we were in for; secondly, we would be spending longer in the tank because we were coming down from a higher velocity than the one we had climbed to at the start. It would only be an extra day and a half, but that was still more than it had been.

  This time we knew enough to remain still most of the time, moving only often enough to avoid developing pressure sores and other such ailments. While we were in there, the ship automatically began to launch probes; because they could stand higher deceleration than we could, they would race into the Kousapex System ahead of us, then fire “throw away” zero point energy rockets to slow them down, and finally arrive on magnetic braking, much as Wahkopem Zomos had, forty-four years before them.

  There were a thousand theories about just what had happened to the crew of Wahkopem Zomos, and it was hard to say which was the least plausible. Contact had drifted over time—the Imperial office in charge of staying in touch with them had had its budget cut over and over, and fallen more and more into the hands of political hacks, so that they often omitted to record blocks of whole eightweeks of data coming back. By the time that whatever it was had happened (actually years after, allowing for the time it took a radio signal to get from Setepos back to Nisu), there were huge gaps in the data.

  We knew Wahkopem Zomos had achieved orbit around Setepos and begun to attempt a landing at one location. Beyond that we had a few other pieces of data, and none of them were of much use. Only three pictures recorded from that landing site had found their way into the database, though it was clear from directories of document titles that the crew of Wahkopem Zomos had sent a great deal of data about it. The pictures appeared to show a crude village from a great distance—but the dates and times on the pictures were obviously wrong since they indicated that the pictures were taken before the explorers landed, and they would have built no such thing anyway—they had more than adequate prefabricated shelters available. So why had they chosen to construct a village big enough for a hundred people, out of native materials?

  Discounting the crackpot theory that the village was actually built by mythical Seteposians, who shot down the Gurix as it tried to land, the most likely explanation was that the pictures were architectural simulations, probably prepared by Priekahm, who was known to have considerable artistic abilities. Probably she had sketched what sort of colony the first settlers might build. Then, of course, the Gurix had crashed, and Wahkopem Zomos had continued slowly transcribing all of its data back to Nisu, eventually sending along those three cryptic pictures.

  The one problem with that theory was that Wahkopem Zomos had continued to relay data from its probes, and some of those probes had continued to operate for years. Only one probe had been in the immediate area of the landing site; most of its pictures simply showed stretches of desert, riverbanks, or forest, as it wandered around the edge of the hills that the ill-fated Gurix had tried to land in.

  But one picture was different; it appeared to show four figures with long sticks crouching in the desert, as if they were stalking the probe itself. Computer enhancement of the picture, it was claimed—though personally I found it just made it fuzzier—marked one of the figures as a Shulathian holding a steam rifle. And since that had been the very last picture from that probe, the crackpots had of course claimed that the crew had survived the crash, that they had joined with the natives, and that for some strange reason they had taken to stalking the probes with steam rifles.

  I didn’t think that the enhancement had even adequately demonstrated that any of the figures were Nisuans, as opposed to shrubbery.

  The other odd piece of data was that the Wahkopem Zomos log of the successive positions of the Gurix seemed to show it at the landing site, making six round trips back to the ship over a period of almost a full local year, and then abruptly somewhere in space, moving at a highly implausible speed if one plotted the successive positions. This was more evidence, at least, that the date and time recording system had become unreliable.

  Our expedition was only the first of many; the People’s Space Exploration Foundation was constructing nine more exploratory ships. The last one of those should be just departing when we arrived back at Nisu, a decade after leaving in Nisu’s time, less than two years by shiptime. We had to get the possible sites for colonies scouted quickly, before the Intruder returned, and the Second Bombardment pounded our civilization to pieces. And we had to hurry about it, after years of time-wasting
by the emperors. Strangely, the Wahkopem Zomos expedition might well save our civilization, because en route it had done a series of gravimetric experiments, using the very long baseline made available by being so far out in space, which had revealed three more habitable worlds within our reach.

  When the crew emerged from the tank we were just a few eightdays from Setepos, and our probes were already orbiting or had landed. The job fell to me of looking through the visuals to see what I could figure out.

  I thought for a moment of being impulsive, getting the first good look by just flipping my viewscreen directly to the view from one of the probes, decided against that, and started the protocol I had written before, a program that would scout through reported probe data and find the most improbable pictures—the ones least like what might have been expected from the data we had from the old Wahkopem Zomos probes.

  The first picture that popped up made me laugh, perhaps to avoid snarling. It showed a patch of sky between trees from high up, through branches. It was plain that the little camera probe had gotten hung up on branches and pointed the wrong way. I clicked to the next one.

  This one showed a flat expanse and distant mountains, taken from a short distance above the flat expanse. It was the only picture that probe had sent after getting under cloud cover. It took me only a moment to realize it had descended into a mountain lake, and since it was another one of the cheap camera probes, it undoubtedly sank to the bottom and was there now, patiently recording whatever swam by, its transmissions not reaching us because of the interference from being underwater.

  There was only one significant anomaly left, but that one was from one of the two functioning rovers. I popped it up on the screen.

  There was a very long moment while I just stared. Then I checked to make sure that someone could not have put this into the interpreted data as a prank. Finally, summoning my nerve, I clicked on the communicator. “Assistant Thetakisus requests Captain Baegess and Political Officer Streeyeptin to come to my console; I have something you should both see.”

  They were there almost instantly. “Sirs,” I said, gesturing at the screen, “this is one of the anomalies from the probes. I’ve verified that it’s genuine. I request that my superior officers confirm to me what I see here.”

  On the screen there were two figures, in a brief loop of motion picture. Apparently the rover had been sitting under a tree, in deep shade; halfway through the short motion picture there was a distinct pop as the rover selected another light level, and the two shadowy figures sprang into sharp relief.

  The one on the right was indisputably female, Nisuan—and a Hybrid. Furthermore, she was too young to be part of the Wahkopem Zomos crew; I wondered for a moment what strange feeling had struck me, and then realized that it was merely the realization that she was pretty.

  The figure on the left was impossible to describe; it might have been a severely deformed Nisuan, or some kind of native animal. But around its neck it wore an object that appeared to be an old communicator—the type the Gurix might have carried, a museum piece on Nisu—pierced with a leather thong. And as the two of them gabbled, staring at the rover, a few words stood out.

  Distinctly, she said “probe,” “camera,” and “Wahkopem Zomos.” The rest of her speech was no language I recognized, but her strange companion seemed to respond in the same language.

  “I think,” Captain Baegess said, “that your place in the history books has just become secure.”

  Streeyeptin gestured his agreement. “You’re in for an extra promotion at the least when we return. Are there more pictures from the same rover?”

  There were not. Like the Wahkopem probe before it, after taking a single intriguing picture, our rover had shut down completely. “Captain,” I said, trying not to smirk, “I request permission to stay up late and get the other rovers working.”

  He granted it without argument.

  2

  THE BIGGEST DIFFICULTY WITH bringing Egalitarian Republic to rest above Setepos was aiming the exhaust.

  As the assistant assigned to the captain, I had seniority over the other two assistants on board, so I was in command of the first step, an honor that would have been nicer if it hadn’t been so dangerous.

  As we plunged into the Kousapex System, still at many times solar escape velocity, decelerating at eighty-eight percent of gravity, we got to work on the first step, unpacking the disperser from storage. Without the disperser, we would not be able to park Egalitarian Republic above Setepos, and though our landers could reach orbital speeds if they had to, it would greatly complicate our operation if they had to orbit and deorbit for every trip up and down. Thus, since our engine could put out many times the thrust needed to counteract Setepos’s gravity for periods of years—after all, it had just done so—we would hover on thrust above the planet’s surface, outside the atmosphere to avoid the turbulence we would cause by superheating the air below us.

  But even with the ship safely out beyond the atmosphere, heat was going to be a big problem. Our engine was a zero-point energy laser, and at the thrust needed to keep us in place, if we just pointed it at the planet’s surface and turned it on, its power output was enough to vaporize rock explosively. (After all, we would be literally standing on a beam of light.) Whatever spot we hovered above, if it were dry land, would swiftly turn into a gigantic volcano.

  The disperser was a device to make the beam spread out enough so that we could safely point it at the ocean surface, and use the boiling water and steam to carry off its enormous load of energy.

  The disperser took three full working days to get to the point where we were ready to begin. Naturally the People’s Space Exploration Foundation, back home, hadn’t seen fit to provide us with a hatch that a complete disperser could go through, or a disperser that could go completed, through our hatches, so we had to check out components, get the three pieces ready to go together, and then plan to assemble them outside in space. All this, of course, without complaining, since you never knew what Streeyeptin might remember once we returned.

  When at last we were sure that all three pieces were working well and could be interfaced to the others, just five days out from Setepos, the captain turned on the antiproton spray and turned off the zero-point energy lasers that had propelled the ship all the way here from Nisu and were now braking us as we came into the Setepos System. Abruptly, the acceleration was zero, and we were weightless.

  The three assistants met with the captain just before we went outside to put the disperser into place. Our being chosen for this part of the mission meant we were “about to set the record for the fastest spacewalk in history,” Captain Baegess pointed out. “We think our system for protecting you will work, but of course this is the time we really find out. At least so far, for the last tenth of a day, nothing big enough to hurt you has hit the ship.”

  “Except the gamma radiation,” Krurix pointed out, voicing what Bepemm and I had been thinking.

  “Except the gamma radiation,” Captain Baegess agreed, “but that’s not nearly the problem that being blown apart would be.”

  Though we were now far below lightspeed, the velocity of our ship was still so high—about ten thousand times that of a slug coming out of a modern steam rifle—that a dust grain delivered more than enough energy to tear one of us in half, and as we were now entering the new solar system, dust was getting thicker outside the ship.

  Inside the ship we had been protected by our deceleration exhaust; any dust that drifted into the zero-point energy laser were either vaporized (if dark), or accelerated away from us at great speed (if reflective). The particles streaming away helped to clear space in front of us as well.

  But we couldn’t work outside with the laser turned on, and so it would not protect us from the dust we would be running into. Instead, the captain had flipped the ship back over so that its nose pointed in the direction we were going again. We would use the antiproton spray that had protected the ship during the long years of ac
celeration.

  The antiproton spray was simply a long tube running through a magnetic coil, pointing out into space ahead of us. There was a big negative charge on the ship end of the tube, and a big positive charge on the far end.

  Because antiprotons have a negative charge, a fine mist of antiprotons sprayed into the tube would accelerate away from the negatively charged ship, follow the lines of the magnetic field down the tube toward the positive charge that attracted them, and shoot out into space at close to lightspeed. When one of them struck a dust speck, a small part of the burst of energy released by the antimatter/matter reaction would be transferred to the speck (like a bomb going off next to a rock) and the speck would shoot off away from us (since the “explosion side” would always be toward us).

  The problem was that while a small part of the energy would move the dust speck, a large part of that energy would become hard gamma rays; those of us outside were going to be exposed to some radiation over and above the usual space crew’s dosage, even with the whole ship between us and the antiproton spray. “That’s why we want you to work fast,” Captain Baegess reminded us for the hundredth time. “Your suits provide some protection, but not nearly as much as being inside the hull of the ship. So get done quickly; we don’t want to have to treat anyone for cancer on the way back, and we want everyone to come back.”

  “Yes, sir,” I said, along with Astrogator’s Assistant Bepemm.

  Engineer’s Assistant Krurix added, “We feel just the same way.”

  The captain had a chronic problem with Krurix, who couldn’t seem to respond to simple orders without making a joke out of them, and Bepemm rolled her eyes at me as if to say, Here we go again, punished for whatever Krurix does, but either the captain was in a good mood or saw the humor in the situation, and said, “Then we’re all in agreement. Good, then. Go get it done.”

  The dispersion coil was simply a big set of superconducting electromagnets forming a lumpy torus; each of us would go outside with one-third of the torus. We would connect the parts together and mount them around the aperture of the laser—all the while taking a certain amount of hard gamma from antiproton reactions that took place far enough out to the sides so that the ship did not shield us from them.