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  “How powerful?” Larry asked.

  “Well, power is one thing we’re trying to measure. We start with a spherical one-gee field one kilometre across here, which we can hold stable for about a millisecond. By the time we concentrate it, collimate and pulse it, we’ve lost most of the power. The wave front spreads as well, weakening the field strength. We’d be happy to end up delivering maybe a ten-millionth of a gee at the other end, but we don’t know what we’ll get.

  “In fact the job tonight is to find out what we can deliver at the other end. The beam isn’t all that well collimated and there’s a hell of a lot of leakage. In theory we should be sending a perfect column of parallel gravity waves. In practise, we’re sending a conical beam, narrow at this end but broadening rapidly as it moves out. And the gee waves aren’t exactly parallel either. We’re guessing that we can deliver a ten-millionth gee, but we’d settle for anything within a factor of ten of that.”

  “And they can detect gravity pulses that small?”

  “We send to those stations because they have the best detectors, the same type we use. The Titan and Ganymede stations are studying the interactions of the gravity fields of Saturn and Jupiter’s satellite families. The Venus station is mapping the gravity field there, trying to use the Solar tidal effect to deduce the planet’s internal structure. And JPL is where they designed the sensors they’re all using. Their detection gear is good, and they use a range of sensitivities. One at low end, a middle range, and a heavy-duty job,” Sondra concluded.

  “Could they measure, say, a millisecond one-tenth push-pull gee burst? Something like that, a million times more powerful that what they’re used to getting from us?”

  Suddenly Sondra understood. “You want to amplify the gee field with your process and then beam it to them!”

  Larry grinned wickedly. “That’ll make them sit up and take notice, won’t it?”

  Sondra thought for a moment, and the more she thought, the more she liked the idea. By its very nature, the experiment would attract attention to Larry’s amplification effect. Attention, hell! It would blow the doors off gravity detectors all over the System. Every gravity researcher between here and the Sun would be certain to hear about it within hours, and all of them would be clamouring for more information, more verification.

  That was Larry’s idea, obviously, to get the news of the Chao Effect off Pluto, spread out as far and wide as possible.

  “It ought to work, Larry,” she said. “No doubt about it, it ought to work. If we can set up the Ring to amplify the gravity field, modulate it, and collimate the gravity waves.”

  “That side of it I know we can do. I’m just worried about their seeing it at the other end and being able to measure it.”

  “Don’t worry about it. All of those labs run their detectors twenty-four hours a day, recording their reading constantly. The detectors are built to operate and record automatically, to prevent a sloppy operator from missing something. If we can send it, they’ll see it.”

  “Then let’s give them something to see,” Larry said, sitting down at the controls.

  ◊ ◊ ◊

  Long before the Ring of Charon was first powered up, astrophysics had ceased to be a strictly observational science. Active experiments, involving massive energies, were common. Not only at the Ring, but at facilities large and small across the System, powerful forces were being explored.

  Unfortunately, there were also many observatories, on Earth and in space, designed to detect incredibly weak signals from millions of light-years away. Too much input could destroy them easily. The high-energy experimenters had it beaten into their heads that they must give broad notification of their plans, offering plenty of time to shut down delicate gear. Failure to do so risked destroying some colleague’s delicate detection gear halfway across the Solar System.

  There was another, more complex reason for thorough warnings of experiments. Back in the old days, when all the observatories were on Earth, or within the orbit of the Moon, it was always possible to call on the phone with late-breaking news, so as to get a second observation of the phenomenon in question. Coordinating observations between two or more observatories was at least reasonably straightforward. Even in cases where the observation had to be synchronized to the nanosecond, there was no great problem when the two points were tiny fractions of a light-second apart. However, the speed of light had changed the forms of etiquette: phones and easy synchronization were out of the question once there were observatories orbiting every planet from Mercury to Saturn. A wave of light energy that passed Saturn might not cross Earth’s path for four hours. A two-way contact, query and reply, would take eight hours.

  Communications workers invented the event radius to handle this sort of problem, and the astronomers eagerly took it up.

  Consider how electromagnetic signals move. All of them move at the speed of light, and unless manipulated by a focusing device, all types of electromagnetic radiation (for example, lightwaves or radio signals) radiate out from a given point on the surface of a sphere that is expanding at the speed of light. Think of a dot drawn on the surface of an inflating balloon. The dot, representing a signal, moves outward, riding the skin of the balloon as it expands.

  The distance between that dot and the center of the balloon, between the surface of the radiative sphere and the center of radiation, is an event radius.

  No data about a given event can be received until the dot, the information, passes through the observer as the information sphere expands at the speed of light. Event radii can be measured in conventional linear measures, but it is generally more convenient to refer to them in light-time. Thus, Earth’s distance from the sun, one hundred fifty million kilometres, is an event radius of about eight light-minutes. If the Sun blew up, Earth would not know it for eight minutes.

  But knowing the light-time distance was not the only problem. At times the situation grew even more frustrating as the movement and gravity wells of the planets themselves introduced slight redshifting problems and microscopic time-dilation effects. More than once, careers were saved or wrecked by the discovery of an error in compensating for those effects.

  Webling had sent out a standard notice of her planned experiment hours before. Larry and Sondra knew they had to send out advance warning of their modifications of the experiment, but they were nervous about doing it. Yet without the warning, they would infuriate any number of other experimenters. Not a good idea for an experiment that was half public relations.

  Sondra drafted the notice to JPL:

  ALERT TO JPL GRAVITY LAB: THIS WILL SERVE AS NOTICE OF A MODIFIED COLLIMATED GRAVITY-WAVE PROCEDURE. TIMES OF TRANSMISSION TO YOU AND OTHER SENSOR LABS UNCHANGED, BUT NEW TECHNIQUE SHOULD PERMIT 10 TO SIXTH INCREASE IN POWER TRANSMISSION. PLEASE RIG FOR MORE POWERFUL INPUT AND ADVISE AFFECTED LABS.

  They sent similar messages to the other participating labs, warning them of the high-power pulse on the way, requesting relay to other facilities that might be affected.

  It seemed more than a bit foolhardy to be doing a secret experiment while providing a general warning that it was about to happen. The speed of light came to their rescue. Sondra was careful to send the alerts through the station’s automated signal system, without any human intervention. Many eyes on many worlds would read their messages, but no one on Pluto would know what was up until queries and replies came back from those labs. And by then, of course, it would be far too late to stop the experiment.

  Figuring in speed-of-light delays, there would be nearly an eight-hour lag between the send-off of the warning to the closest lab on Saturn, and the earliest possible response back to Pluto.

  That should serve as protection enough, so long as no one at the base noticed what they were up to in real time. To avoid that problem, Sondra and Larry agreed to stay as close as possible to Webling’s original experiment design, in the hope of avoiding premature attention.

  Given the difficulties of aiming the untested graser system
, Webling had designed the original run to hit the closest, easiest target first and work out to longer range from there. The positions of the planets dictated that Saturn be the first target. Sondra used the original aiming data as she set up the run.

  It was a complicated job. She glanced again at the chronometer when she was halfway through it. Three hours until this control room had its shot at the Ring. She sighed and went back to the complex job of resetting the controls.

  ◊ ◊ ◊

  With a beep and a flashing green light, the control panel announced that the Ring was ready for the graser run.

  With ten minutes to spare, the myriad magnets, coolant pumps, mass drivers, particle accelerators and other components of the Ring system were configured to form a Chao Effect-amplified gravity well, to modulate and to collimate the gravity waves from it, and to fire tight pulses of collimated gravity power toward Titan.

  Or at least, Sondra thought they were ready. She took another look at the control system. This was definitely a wild setup. No wonder the station’s old fogies hadn’t been able to believe it.

  The countdown clock came on and started marking the passage of time. Eight minutes left.

  Larry sighed and rubbed his weary eyes. Now it came down to one last set of checks to make, and one last button to push.

  One last button.

  They could have programmed those last checks on the automatic sequencer as well, even told the computer to start the actual firing of the system. If the experiment had been dependent on split-second timing, they would have.

  But timing wasn’t that vital here. Besides, letting the computer do the work would not have been right. This was a human moment, the triumph both of human ingenuity over a technical and scientific problem, and of human cussedness over damn-fool rules. It was a way to proclaim a breakthrough to all humanity—and, equally important to Larry, it was a way to thumb his nose at Raphael. No computer could be programmed to do that properly.

  Seven minutes left.

  Still, there was something about the moment that surpassed even Larry’s deep-seated need to defy the director. It was dawning on Larry that this wasn’t just an experiment, not just an attention-getting device for saving their careers. This was history. No one had ever attempted such a thing. This was gravity control on a grand scale. Crude, limited—yes. But this one moment could change everyone lives.

  Six minutes.

  Just how ready was he to change the course of history? Larry licked his dry lips and glanced nervously over at Sondra. She nodded once, without looking up from her readouts. Everything was ready. In nervous silence, the last few minutes slid away to seconds. And then it came to the time itself.

  For a brief moment, a frightened voice in Larry’s head told him no, told him not to do this thing. He ignored the voice of fear, of caution, and stabbed the button down.

  Thousands of kilometres over his head, the Ring activated the gravity containment, and then pulsed the first waves of gravity power toward Saturn. Larry pulled his finger from the button and looked around blankly, feeling the moment to be a bit anticlimactic. There should have been some dramatic effect there in the lab to make them know it had happened. Maybe I should have programmed the lights to dim or something, he told himself sarcastically.

  Of course, nothing happened in the control room. The action was far away overhead, at the axis, the focal point, of the Ring of Charon.

  But by now, the action was rushing its way down toward Saturn. The first pulse was already millions of kilometres along its way.

  From here on, the automatics did take over. The sequencer fired again. The second millisecond pulse leapt from the Ring. And the third, the fourth. It was too late to bring it back. Far too late. There was nothing they could do but press on. They would catch hell no matter what they did now.

  ◊ ◊ ◊

  The Observer had no concept of free choice. All that it did, or thought, or decided, it was compelled to do, each stimulus producing the appropriate response. There would not be, could not be, any situation not provided for. In its memory and experience, going back far beyond its own creation, all was supposed to be categorised, understood, known. There should have been nothing new under this or any other star.

  It could not fear the unknown, because such a concept was beyond it. To it, the unknown was inconceivable.

  Thus, it struggled to force new phenomena into old categories—for example, choosing to see the alien ring as a mutation, a modification of its own form.

  Having reached this flawed identification, it accessed the concept of change and mutation as recorded in its memory store. It explored the possible forms change might take, and the results of those changes. As best it could tell, the alien fit within the possible parameters. That was enough data to satisfy the Observer.

  It only remained to determine what its distant cousin was doing. But then, the answer arrived, full-blown and complete, from its heritage memory store.

  It was a relay. It was echoing a message from home, announcing that it was time. Perhaps the normal means of contact had failed, and this new ring had sailed between the stars to bring its message.

  Of course. What else could it be? The Observer searched the length and breadth of its memory, and did not find an alternative answer.

  To one of the Observer’s kind, memory was all. Finding no other answer in its memory proved there was no other answer.

  It was a way of being that had always worked.

  ◊ ◊ ◊

  Jupiter was next, or rather Ganymede. Larry told himself he must remember not to treat the inhabited satellites as mere appendages of the planets. The residents of the gas-giant satellite settlements were always annoyed by that sort of thing. After all, no one referred to the Moon as being part of Earth. Titan, Ganymede and the other inhabited satellites were worlds in their own right. Larry knew he had best bear that in mind—if things worked out the way they might, he would have a lot of contact with the gravity experts on Titan and Ganymede.

  Yeah, those are vital points right now, Larry thought sarcastically. He was finding other things to worry about, trying to avoid the big picture. He had caught himself doing that all night, again and again. He was unable to face the meaning, the consequences of what he was doing. He did not want to be in charge of changing the world. The hell with it. Larry plunged in the start button again. The beam regenerated itself and leapt toward Jupiter’s satellite.

  At least, they hoped it was heading toward Ganymede. Though Sondra had run graser experiments before, they were at a ten-millionth of this power. She was finding the collimated gravity beam difficult to control even with computer-automated assistance and Larry to backstop her.

  And, be it confessed, she too was more than a bit nervous about dealing with such massive amounts of power. Even with all the signal loss and fade-outs of their crude directionalising system, they were still pulsing bursts of three hundred thousand gravities out from a point source—albeit a point source smaller than an amoeba, a point source that went unstable after a few seconds. A million kilometres from the Pluto-Charon system, the pulse had lost half its power, and lost half again in another million.

  By the time it reached even the closest of its targets, the beam had lost virtually all its power, was reduced to a one-millisecond tenth-gee wisp of nothing. And since it was phased with the repulser beam, the net gravitational energy directed at a target was exactly zero. The beam pushed exactly as hard as it pulled. It was physically impossible for the beam to be anything but harmless. Besides, each beam firing only lasted a millisecond and acted on the entire target body as a whole. The beam was a push-pull type, she told herself again. The push-pull couldn’t fail, not without the entire system failing utterly. It was impossible for this beam to hurt anyone or anything.

  But such reassurances weren’t enough to keep her from getting nervous. “How’s it going, Larry?” she asked for what seemed like the hundredth time.

  “Still fine,” Larry replied, more than
a bit distracted himself. The amplified gravity source still collapsed every thirty seconds or so, and Larry had to regenerate the point source. The strain was getting to him. He had hoped to automate the process, but he had rapidly discovered that he barely had time to look up from his primary controls before the source would go unstable again.

  It wasn’t until halfway through the Jupiter run that he had the time to set up the automation system. He instructed the computer to look over his shoulder, figuratively speaking, and watch the regeneration procedure he used.

  After the seventh or eighth time, the computer had “learned” the regen procedure in most of its permutations and was able to take over the job itself. Larry breathed a sigh of relief and leaned back in his chair. They were on their way.

  He wondered what their reactions would be—especially what the Jet Propulsion Laboratory would think.

  The speed of light was the limiting factor now. Gravity waves moved at lightspeed, just like any other kind of radiation. At the moment, Pluto, Saturn, and Jupiter were all roughly lined up one side of the Sun, with Venus and Earth on the other sides of their orbits, only a few degrees away from the Sun. Of the planets in question, Saturn was currently the closest to Pluto, and Earth the furthest away.

  Larry frowned and scribbled a quick diagram on a scratch pad to help him keep it all straight. After a few brief calculations, he added the round-trip-signal time in hours for each planet.

  planet position Earth Venus Sun Jupiter Saturn Pluto

  station JPL VISOR - Ganymede Titan GRS

  round trip signal

  time in hours

  from Pluto 11.2 11.1 - 9.4 8.27 0

  Those were round-trip-signal times. So Titan Station, orbiting Saturn, would receive its dose of gravity waves in just over four hours. Even if Titan signaled back to Pluto immediately when the gravity waves arrived, it would still take more than four more hours for Pluto to get the word.