Encounter With Tiber Page 11

  François nodded, gulping for air. “Peter, I think you’re going to have to apologize to whoever called.” He pushed his unruly dark hair back and stretched in the low gravity. “Practically every antenna in the Southern Hemisphere has been getting it.”

  “I think probably everyone will want to talk with their home countries and institutions,” Tatiana said. “And this time was allocated as down time, for the arrival of the Pigeon, so for the next hour and ten minutes, none of us has anything much we are supposed to be doing. If you don’t mind cutting the welcoming party short, we could all get onto communications links and see how much we can learn about this whole situation.”

  “I feel as welcome as I need to,” Lori said. “And Chris will explode if he has to sit here and make small talk while anything like this is happening. Let’s do it.”

  Haldin grinned. “Chris is not the only one who would explode. Well, at the least, let’s take this time and let everyone talk to home. The next thing after that is supposed to be dinner and rest, so let’s make dinner a general meeting where we pool our information.”

  Chris found that it was easy enough to find people who knew the basics, but seemingly impossible to find anyone who knew more than that, by phone. And the basics were scanty: sometime within the last twenty-four hours, on a wavelength of about 96 meters, a signal had begun to come in strongly from the direction of Alpha Centauri, the triple star, which is the closest star to the Earth. Bits and pieces of the signal seemed to be strangely ordered—it appeared to be a sequence of tones, two different pitches stuttered at an enormous rate—but unfortunately the Earth’s atmosphere is nearly opaque to radio at that wavelength, because it cannot penetrate the ionosphere. Thus it was impossible to catch more than brief snatches of it on even the most sensitive radio telescopes on the ground.

  Theories abounded. The media, naturally, was already claiming that it was messages from aliens; other hypotheses included various strange events in the stellar atmosphere of Alpha Centauri A or Alpha Centauri B, somehow causing one star or the other to act as a giant laser at that wavelength; a huge electrical storm in the atmosphere of a planet circling those stars; the gravity of Alpha Centauri A acting as a lens and focusing radio at that wavelength from a distant source, thus making it seem louder; and many more. The idea that it might be aliens was discounted by many, not just because of the sheer improbability, but also because it didn’t seem likely that an intelligent species would try to contact others using radio on a wavelength that would be mostly blocked by the water-vapor-rich atmosphere of any planet with life.

  All of these theories suffered mainly from the problem that little could really be known directly about Alpha Centauri. Alpha Centauri is the nearest star, but “near” is a relative term; it’s like saying that Key West is the nearest part of the United States to the South Pole. At the speed at which the Apollo astronauts went to the Moon, it would take a little less than 110,000 years—time enough for the last four Ice Ages—for a spaceship to get from Earth to Alpha Centauri. A radio signal, which is 26,500 times faster, takes about four years.

  Physically Alpha Centauri is not one star but three: Alpha Centauri A, a star very slightly larger than our Sun; Alpha Centauri B, a smaller star that is only a few astronomical units from A; and Proxima Centauri, a very dim, cool, small star which is so far away from A and B that astronomers debate whether it is really in orbit around them or just moving around the galactic center in an almost identical orbit.

  A and B orbit around their common center of mass—a point in empty space where the average of their masses would be if they were one single body—about every eighty years. In their endless slow waltz, A and B sometimes get as close as eleven AU to each other (ten percent farther than the distance from the Sun to Saturn) and sometimes swing out as far as thirty-five AU (sixteen percent farther than the distance from the Sun to Neptune).

  Chris called a dozen colleagues before it was time for the scheduled dinner on ISS; most of the people he called knew no more than he did. An hour on the phone produced only a list of people to call for the next day.

  Other people had had better luck. When they all gathered for sandwiches and squeeze bags of soup an hour later, there were a few other pieces of information which people had extracted.

  First of all, there were occasional long repetitive strings in the signal, sometimes with only small variations, sometimes with no variations at all. It was believed that it might be repeating on a cycle of hours or days in length, but there was so much noise that it might take months to get a copy of the whole signal—if it stayed on that long and if it was indeed repeating. It was clearly not the product of static discharges in an atmosphere anywhere—unless somehow a gas giant planet in that system had a lasable atmosphere that had spontaneously tuned itself to that frequency. The best guess was that the power level at which it was coming in was actually remarkably uniform.

  Everyone was enjoying throwing in theories when the chime sounded for the phone. Tatiana, as commander, picked it up; a moment later she put it up on speakers.

  “No doubt you’ve heard,” said a voice with a Midwestern drawl that Chris recognized at once as the chairman of the University Space Research Associates, “about the noise from Alpha Centauri. Is Dr. Terence there?”

  “Yes, I am, Bob.”

  “Well, in the last few hours some big changes have happened. When the radio noise from Alpha Centauri began, several observatories in the Southern Hemisphere contacted the Center for Short-Lived Phenomena, and they called the USRA, and NASA, with a suggestion. You have the FSRT, which is the most sensitive radio detector ever constructed. Moreover, you are sitting above the Earth’s atmosphere, which is to say you can get clear reception of the radio signal now emanating from Alpha Centauri. Of course it would be best if the FSRT were already in place on the Moon, since that would allow us to take advantage of the conditions there, but the fact is that conditions at ISS are better for radio observations in the millimeter wavelength than they are anywhere on Earth, ever. And we don’t know how long the signal will last. Thus NASA has authorized us to modify our test for the FSRT; we are asking that you immediately mount a loop antenna, running the length of the truss, and connect that to the FSRT, then attempt to record the signal now coming from Alpha Centauri. A full set of directions and specifications, plus orders from everyone’s national governments, will follow immediately by datalink. You’re going to go out there and get a good copy of that signal for us.”

  “I—thank you,” Chris said. “I’m looking forward to it.”

  “We’re very fortunate that you happened to be there with the appropriate tool,” the chairman said. “Orders follow, as they say; good luck.” With a sharp click, the call was disconnected.

  “So all we have to do is make a 90-meter loop antenna,” Lori said, “out of whatever we just happen to have brought along.”

  “And rig it overnight,” Chris added. “And have the FSRT work perfectly during its tryout—”

  “Besides,” Denisov added, “you may not recall this, but due to budget cutbacks years ago in your country, there is nowhere on the outward-facing part of the truss to mount any equipment whatsoever—we can’t do any kind of real astronomy here on the station.”

  “I had forgotten that there aren’t any brackets or places to attach things on that side of the station,” Chris admitted.

  Haldin seemed to think for the space of three long breaths, and then she shrugged. “Well, it will do all our careers some good if it works, and hurt nothing if it doesn’t.”

  Denisov nodded. “And we do have a small stock of supplies. We have some large clamps and some insulated wire, probably enough to mount a loop on the outward-facing surface of the truss. Do you have any way of connecting to such a loop?”

  “Some of the test circuit stuff takes standard plugs,” Chris said. “Yeah, I think so.”

  “Then let’s get to work on it,” Haldin said. “We need to work out the technical details now.”<
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  After a six-hour nap, Chris found himself going out for an EVA with Peter Denisov. Despite the apparent grumpiness of the heavyset Russian, Chris was getting to like him; he’d come to realize that the cosmonaut was intolerant of nonsense and convinced of his own judgment, but more than willing to adopt a good idea once he was convinced of it. (I sometimes have odd memories of him—he used to come and visit my father, and the two of them would go out on the town, usually with women my father had found from wherever it was that he turned them up; I can remember my mother claiming that he must be subscribing to the Bimbo of the Month club. Then the next day Peter would be down in the basement at the workbench with me, helping me put together a model, or we’d be out in the woods riding minibikes, or a thousand other things—for an old grouch, Peter Denisov was pretty good at acting like a teenager.)

  The airlock was tiny, really just a small attachment onto a hatch, and the two men had to go through it separately, each tucking himself and his bulky spacesuit into the small, closet-sized space, half-squatting, waiting for the air to be pumped out of the lock and back into the Big Can, then opening the outer door and climbing out with a bag of supplies and closing the outer door behind himself. Denisov, as the more experienced of the two, went first, and when Chris emerged and closed the hatch, he was already set up and ready to go. “Before we start,” Denisov said, his voice crackling through the radio in Chris’s helmet, “is this your first EVA?”

  “First one,” Chris agreed. “We’ve all had the training, but I’m sure that—”

  “I’m sure you’ll be fine, too,” Peter replied. “Tatiana, cut the floodlights please.”

  “Roger,” her voice crackled in their headsets.

  “Now, Chris,” Peter said, “I just wanted to suggest that you look up away from the Earth for a moment or two. It’s a view every astronomer should have.”

  I know what he saw, now, and can understand a little of how it must have struck him; when I was a kid and Dad would describe being outside in space for the first time, I didn’t understand why he was so excited about there being “so many stars” when after all he was an astronomer and he should have known how many of them there were anyway. Now I have a little more idea that when you have imagined something but never really seen it directly, for your whole life, just possibly the first time you see it may strike you dumb.

  They spent the ten minutes, while they waited to come around to the day side of the orbit, looking up into the stars, many times as many as you can see from Earth, the bright ones brighter by far than earthly eyes are used to. They had something pretty important to do, and no doubt they were strongly reminded of that by the brilliant beacon of Alpha Centauri—so close that even though it’s just a run-of-the-mill double star with a combined brightness only about one and a half times our own Sun, it’s still the third brightest star in our sky.

  Chris waited, floating with one hand to hold him in place, till the Sun emerged over the Earth; in less than a minute, the glare on his visor erased the swarm of stars, leaving the sky black. The job was simple—or it would have been simple, on Earth. Nothing is simple in orbit, where the rules wired into your nerves by half a billion years of evolution stop working, and you’re encumbered by a thick, heavy pressure suit. The HT-based habitat was attached to the center node, aft of the truss (a long, thin structure on which the immense bank of solar panels that powered the station was mounted). The truss itself had a hexagonal cross section as wide as a hallway in an ordinary house; normally if one had to get to either end of it, one either climbed from strut to strut, along the structural members, inside the truss, or worked tethered to one of the structural members and crawled along the “bottom” (Earth-facing) side, when there were Earth-monitoring or space-science experiments to be conducted.

  As the Russians had pointed out, one of the many budget cuts the American Congress had imposed on the ISS had involved planning for a truss that was only “half useful,” in that there were no built-in places to attach experiments or equipment that faced out toward space. The United States, having successfully lured other nations into the cooperative enterprise, had almost at once begun to limit its capabilities, like a used car salesman who shows you something too good to be true and then tries to talk you into taking something grossly inferior for the same price. I can remember Dad growling to himself, after the mission was over, that a few hundred ex-lawyers in Washington had decided that everything interesting in the universe had to be in the same direction, the one that allowed orbiting astronauts to take photographs of their districts.

  As a result, Chris’s first EVA was an interesting exercise in improvisation. Station supplies had included a few dozen Clancy clamps, toothed clamps on a piece of pipe that tightened their grip when a small disk on the pipe was spun to the right, and a large roll of vacuum-proof silver bell wire. (To work in space, bell wire couldn’t have just an ordinary plastic jacket, because many plastics in a vacuum outgas the volatiles that keep them soft; hence, the insulation on the wire was a special fiberglass. And because the expense of getting the wire into orbit and the special insulation was already so high, it only added a small fraction to the cost to make the conductor out of extremely pure silver, which was both a better conductor and more flexible than copper or aluminum.) A small committee of experienced engineers and machinists had spent a long time figuring out what ought to be in the ISS’s tool and supply kits; so far their record was holding up.

  If the truss had been on the ground, it might have taken Chris alone only a few minutes to accomplish the basic job of putting a loop of bell wire onto its space-facing side with the Clancy clamps—he would only need to stretch a few meters of the wire along the girder, put a clamp over it, spin the disk, and move on to repeat the process.

  But on the ISS, that required a whole set of other actions. First of all, attached to the structure itself by their tethers, Chris and Denisov were effectively co-orbiting with the station—that is, they were bodies occupying their own separate orbits around the Earth that happened to coincide, mostly, with that of the station. Thus there was a tendency, because co-orbiting is never perfect, for things to slowly drift to different positions. Everything, including Peter and Chris, had to be on a tether all the time, and tended to drift to the end of the tether, or to wrap around the girders.

  Then there was the matter of having something to push against. If you twist on the disk of a Clancy clamp on Earth, the disk turns easily and the clamp fastens, because the force of your hand turning the disk encounters very little resistance, and the equal and opposite force twisting the soles of your feet in the opposite direction is easily overcome by the friction of your shoes. But in space there’s nothing to control that opposite force; as you turn the disk, the disk turns you, unless you hold yourself in place with your other hand.

  Thus as Chris and Denisov worked their way out to one end of the truss, back to the other end, and then back to the habitat, they had to perform many more tasks than they would have had to do to accomplish the equivalent job on Earth. First, they would move forward to tether themselves, the bag of Clancy clamps, and the coil of bell wire into position. Then they would move back to detach the tethers from their previous positions, and then forward again so that finally after several minutes they were in position to accomplish any progress.

  Then Denisov would take the coil of bell wire and stretch about five meters of wire along the girder, using the previously attached clamps to anchor it behind him and holding onto the girder with his outspread arms wrapping around up toward his shoulders, putting his hands on the “top” so that the wire was held in place where it could be clamped. Then Chris would tow the bag of clamps over, fish out one (with one hand, while hanging on with the other), clip the clamp to his own suit for a moment, close the bag and release it, take the clamp off its clip, fit it over the wire Denisov was holding, brace himself with his other hand, and spin the disk to tighten the clamp.

  After that they would repeat the process again.
It took them about six hours in all—plus an extra twenty minutes or so spent in fetching more supplies.

  When Chris climbed back in, he ached in an amazing array of places from the use of so many muscles in such unfamiliar ways, and his coverall under his pressure suit was drenched with sweat. By universal agreement, Chris and Peter got an extra shower that day; theoretically they should then have napped, but within minutes of getting into a fresh coverall, Chris had swallowed some freeze-dried coffee and aspirin, and was on the job of getting the FSRT plugged into the external contact system that Tatiana Haldin and Lori had set up to use the big-loop antenna. In less than an hour, fiddling and scanning, François and Chris had managed to bring in the signal from Alpha Centauri.

  When they were sure that the signal was coming in clear, the data were being recorded, the datalink to groundside was working, and that the FSRT was behaving as it should, Chris stretched and said, “Well, now, finally, I’m going to use some of that flexibility they say we have, and take that nap.”

  By the time Chris arose, the hypothesis that it was an alien signal had gone from the least likely (at least to the well-informed and scientifically literate) to the most likely. François briefed him as he gobbled a quick breakfast.

  “They say it is coming in in a high tone/low tone/blank pattern; if we assume the blanks are spaces, then since it is coming as triple beeps, it looks very much like a transmission in base eight.”

  Base eight, Chris thought; there’s the first clear evidence that it’s really aliens—or at least that if it’s a hoax, someone has really thought the hoax through. The most common numbering system on Earth is base ten. That is we have ten digits, zero through nine, and each place in a number (counting left from the decimal point) represents a power of ten—5280 is 5 x 103 + 2 x 102 + 8 x 101 + 0 x 100, or as we say it out loud, “Five thousand two hundred eighty”—so casually that we don’t tend to remember there’s multiplication and addition in there, five thousands plus two hundreds plus eighty (which is the swallowed English pronunciation of the original “eight tens”). More recently the computer industry has taught many people to work in “hexadecimal”—base sixteen, in which there are sixteen digits (1–9 plus A–E, representing 10–15 respectively), or in bytes, which are base 256 numbers for practical purposes. (16 and 256 are both powers of two, and because the basic machinery of computers, down at the microscopic level, works on binary [base 2] numbers, this makes for compact information storage; if they were not powers of two, some combinations of symbols would have to be meaningless within the system, thus “wasting” some of the potential information it could carry.)