"Diaspora" - читать интересную книгу автора (Иган Грег)

4. Lizard heart

Bullialdus observatory, Moon

24 046 104 526 757 CST

2 April 2996, 16:42:03.911 UT

Karpal lay on his back on the regolith for a full lunar month, staring up into the crystalline stillness of the universe and daring it to show him something new. He’d done this five times before, but nothing had ever changed within reach of his unaided vision. The planets moved along their predictable orbits, and sometimes a bright asteroid or comet was visible, but they were like spacecraft wandering by: obstacles in the foreground, not part of the view. Once you’d seen Jupiter close-up, firsthand, you began to think of it more as a source of light pollution and electromagnetic noise than as an object of serious astronomical interest. Karpal wanted a supernova to blossom out of the darkness unforeseen, a distant apocalypse to set the neutrino detectors screaming—not some placid conjunction of the solar system’s clockwork, as noteworthy and exciting as a supply shuttle arriving on time.

When the Earth was new again, a dim reddish disk beside the blazing sun, Karpal rose to his feet and swung his arms cautiously, checking that none of his actuators had been weakened by thermal stress. If they had, it wouldn’t take long for his nanoware to smooth away the microfractures, but each joint still needed to be tested by use in order to notice the problem and call for repairs.

He was fine. He walked slowly hack to the instrumentation shack at the edge of Bullialdus crater; the structure was open to the vacuum, but it sheltered the equipment to some degree from temperature extremes, hard radiation and micrometeorites. Looming behind it was the crater wall, seventy kilometers wide; Karpal could just make out the laser station on top of the wall, directly above the shack. The beams themselves were invisible from any vantage, since there was nothing to scatter the light, but Karpal couldn’t picture Bullialdus from above without mentally inscribing a blue L, a right-angle linking three points on the rim.

Bullialdus was a gravitational wave detector, part of a solar-system-wide observatory known as TERAGO. A single laser beam was split, sent along perpendicular journeys, then recombined; as the space around the crater was stretched and squeezed by as little as one part in ten-to-the-twenty-fourth, the crests and troughs of the two streams of light were shifted in and out of alignment, causing fluctuations in their combined intensity which tracked the subtle changes of geometry. One detector, alone, could no more pinpoint the source of the distortions it measured than a thermometer lying on the regolith could gauge the exact position of the sun, but by combining the timing of events at Bullialdus with data from the nineteen other TERAGO sites, it was possible to reconstruct each wavefront’s passage through the solar system, revealing its direction with enough precision, usually, to match it to a known object in the sky, or at least make an educated guess.

Karpal entered the shack, his home for the last nine years. Nothing had changed in his absence, and little had changed since his arrival; the racks of optical computers and signal processors lining the walls looked as gleamingly pristine as ever, and his emergency spares kit and macro repair tools had barely been moved from where he’d first placed them. He wasn’t quite alone on the moon—there were a dozen gleisners doing paleoselenology up at the north pole—but he was yet to receive a visitor.

Almost every other gleisner was in the asteroid belt, either working on the interstellar fleet, providing some kind of support service, or generally playing camp follower. He could have been there himself, in the thick of it—the TERAGO data was accessible anywhere, and being physically present at one site offered few advantages when overseeing repairs for all twenty—but he’d been tempted by the solitude here, and the chance to work without distractions, devoting himself to a single problem for a week, or a month, or a year. Lying on the regolith gazing up at the sky for a month at a time hadn’t been in his original plans, but he’d always expected to go slightly crazy, and this seemed like a mild enough eccentricity. At first, he’d been afraid of missing an important event: a supernova, or a distant galactic core’s black hole swallowing a globular cluster or two. Every speck of data was logged, of course, but even when the gravitational waves had taken millennia to arrive there was a certain thrill of immediacy about monitoring them in real time; to Karpal, now was a transect of space-time ten billion years deep, converging on his instruments and senses at the speed of light.

Later, the risk of being away from his post became part of the attraction. Part of the dare.

Karpal checked the main display screen, and laughed softly in pulse-coded infrared; the faint heat echoed back at him from the walls of the shack. He’d missed nothing. On the list of known sources, Lac G-1 was highlighted as showing an anomaly but it was always showing anomalies; this no longer qualified as news.

As well as recording any sudden catastrophes, TERAGO was constantly monitoring a few hundred periodic sources. It took an event of rare violence to produce a burst of gravitational radiation sufficiently intense to be picked up halfway across the universe, but even routine orbital motion created a weak but dependable stream of gravitational waves. If the objects involved were as massive as stars, orbited each other rapidly, and weren’t too remote, TERAGO could tune into their motion like a hydrophone eavesdropping on a churning propeller.

Lacerta G-1 was a pair of neutron stars, a mere hundred light years away. Though neutron stars were far too small to be observed directly—about twenty kilometers wide, at most—they packed the magnetic and gravitational fields of a full-sized star into that tiny volume, and the effects on any surrounding matter could be spectacular. Most were discovered as pulsars, their spinning magnetic fields creating a rotating beam of radio waves by dragging charged particles around in circles at close to lightspeed, or as X-ray sources, siphoning material from a gas cloud or a normal companion star and heating it millions of degrees by compression and shock waves on its way down their tight, steep gravity well. Lac G-1 was billions of years old, though; any local reservoir of gas or dust which might have been used to make X-rays was long gone, and any radio emissions had either grown too weak to detect, or were being beamed in unfavorable directions. So the system was quiet across the electromagnetic spectrum, and it was only the gravitational radiation from the dead stars' slowly decaying orbit that betrayed their existence.

This tranquillity wouldn’t last forever. G-1a and G-1b were separated by just half a million kilometers, and over the next seven million years gravitational waves would carry away all the angular momentum that kept them apart. When they finally collided, most of their kinetic energy would be converted into an intense flash of neutrinos, faintly tinged with gamma rays, before they merged to form a black hole. At a distance, the neutrinos would be relatively harmless and the "tinge" would carry a far greater sting; even a hundred light years would he uncomfortably close, for organic life. Whether or not the fleshers were still around when it happened, Karpal liked to think that someone would take on the daunting engineering challenge of protecting the Earth’s biosphere, by placing a sufficiently large and opaque shield in the path of the gamma ray burst. Now there was a good use for Jupiter. It wouldn’t he an easy task, though; Lac G-1 was too far above the ecliptic to be masked by merely nudging either planet into a convenient point on its current orbit.

Lac G-1’s fate seemed unavoidable, and the signal reaching TERAGO certainly confirmed the orbit’s gradual decay. One small puzzle remained, though: from the first observations, G-la and G-1b had intermittently spiraled together slightly faster than they should have. The discrepancies had never exceeded one part in a thousand—the waves quickening by an extra nanosecond over a couple of days, every now and then—but when most binary pulsars had orbital decay curves perfect down to the limits of measurement, even nanosecond glitches couldn’t be written off as experimental error or meaningless noise.

Karpal had imagined that this mystery would be among the first to yield to his solitude and dedication, but a plausible explanation had eluded him, year after year. Any sufficiently massive third body, occasionally perturbing the orbit, should have added its own unmistakable signature to the gravitational radiation. Small gas clouds drifting into the system, giving the neutron stars something they could pump into energy-wasting jets, should have caused Lac G-1 to blaze with X-rays. His models had grown wilder and more daring, but all of them had come unstuck from a lack of corroborative evidence, or from sheer implausibility. Energy and momentum couldn’t just be disappearing into the vacuum, but by now he was almost ready to give up trying to balance the books from a hundred light years away.

Almost. With a martyr’s sigh, Karpal touched the highlighted name on the screen, and a plot of the waves from Lacerta for the preceding month appeared.

It was clear at a glance that something was wrong with TERAGO. The hundreds of waves on the screen should have been identical, their peaks at exactly the same height, the signal returning like clockwork to the same maximum strength at the same point on the orbit. Instead, there was a smooth increase in the height of the peaks over the second half of the month—which meant that TERAGO’s calibration must have started drifting. Karpal groaned, and flipped to another periodic source, a binary pulsar in Aquila. There were alternating weak and strong peaks here, since the orbit was highly elliptical, but each set of peaks remained perfectly level. He checked the data for five other sources. There was no sign of calibration drift for any of them.

Baffled, Karpal returned to the Lac G-1 data. He examined the summary above the plot, and sputtered with disbelief. In his absence, the summary claimed, the period of the waves had fallen by almost three minutes. That was ludicrous. Over 28 days, Lac G-1 should have shaved 14.498 microseconds off its hour-long orbit, give or take a few unexplained nanoseconds. There had to he an error in the analysis software; it must have become corrupted, radiation-damaged, a few random bits scrambled by cosmic rays somehow avoiding detection and repair.

He flipped to a plot showing the period of the waves, rather than the waves themselves. It began as it should have, virtually flat at 3627 seconds, then about 12 days into the data set it began to creep down from the horizontal, slowly at first, but at an ever-increasing rate. The last point on the curve was at 3456 seconds. The only way the neutron stars could have moved into a smaller, faster orbit was by losing some of the energy that kept them apart—and to be three minutes faster, instead of 14 microseconds, they would have needed to lose about as much energy in a month as they had in the past million years.

"Bollocks."

Karpal checked for news from other observatories, but there’d been no activity detected in Lacerta: no X-rays, no UV, no neutrinos, nothing. Lac G-1 had supposedly just shed the energy equivalent of the moon annihilating its antimatter double; even a hundred light years away, that could hardly have passed unnoticed. The missing energy certainly hadn’t gone into gravitational radiation; the apparent power increase there was just 17 percent.

And the period had fallen about 5 percent. Karpal did some calculations in his head, then had the analysis software confirm them in detail. The increasing strength of the gravitational waves was exactly what their decreasing period required. Closer, faster orbits produced stronger gravitational radiation, and this impossible data agreed with the formula, every step of the way. Karpal could not imagine a software error or calibration failure that could mangle the data for one source only while magically preserving the correct physical relationship between the power and frequency of the waves.

The signal had to he genuine.

Which meant the energy loss was real.

What was happening out there? Or had happened, a century ago? Karpal looked down a column of figures showing the separation between the neutron stars, as deduced from their orbital period. They’d been moving together steadily at about 48 millimeters a day since observations began. In the preceding twenty-four hours, though, the distance between them had plummeted by over 7,000 kilometers.

Karpal suffered a moment of pure vertiginous panic, but then quickly laughed it off. Such a spectacularly alarming rate of descent couldn’t be sustained for long. Apart from gravitational radiation, there were only two ways to steal energy from a massive cosmic flywheel like this: frictional loss to gas or dust, giving rise to truly astronomical temperatures—ruled out by the absence of UV and X-rays—or the gravitational transfer of energy to another system: some kind of invisible interloper, like a small black hole passing by. But anything capable of absorbing more than a fraction of G-1’s angular momentum would have shown up on TERAGO by now, and anything less substantial would soon he swept away, like a pebble skipping off a grindstone, or blown apart like an exploding centrifuge.

Karpal had the software analyze the latest data from TERAGO’s six nearest detectors, instead of waiting an hour for the full set to arrive. There was still no evidence of any kind of interloper—just the classical signature of a two-body system—but the energy loss showed no sign of halting, or even leveling off.

It was still growing stronger.

How? Karpal suddenly recalled an old idea which he’d briefly considered as an explanation for the minor anomalies. Individual neutrons were always color neutral: they contained one red, one green and one blue quark, tightly bound. But if both cores had "melted" into pools of unconfined quarks able to move about at random, their color would not necessarily average out to neutrality everywhere. Kozuch Theory allowed the perfect symmetry between red, green, and blue quarks to be broken; this was normally an extremely fleeting occurrence, but it was possible that interactions between the neutron stars could stabilize it. Quarks of a certain color could become "locally heavier" in one core, causing them to sink slightly until the attraction of the other quarks buoyed them up; in the other core, quarks of the same color would be lighter, and would rise. Tidal and rotational forces would also come into play.

The separation of color would be minute, but the effects would be dramatic: the two orbiting, polarized cores would generate powerful jets of mesons, which would act to brake the neutron stars' orbital motion a kind of nuclear analogue of gravitational radiation, but mediated by the strong force and hence much more energetic. The mesons would decay almost at once into other particles, but this secondary radiation would be very tightly focused, and since the view from the solar system was high above the plane of Lac G-1’s orbit the beams would never be seen head-on. No doubt they’d become spectacularly visible once they slammed into the interstellar medium, but after only 16 days they’d still he traveling through the region of relatively high vacuum that the neutron stars had swept clean over the last few billion years.

The whole system would be like a giant Catherine wheel in reverse, with the fireworks pointing backward, opposing their own spin. But as they bled away the angular momentum that kept them apart, gravity would draw them tighter and they’d whip around faster. The nanosecond glitches in the past might have involved small pools of mobile quarks forming briefly, then freezing back into distinct neutrons again, but once the cores melted completely it would be a runaway process: the closer the neutron stars came to each other, the greater their polarization, the stronger the jets, the more rapid their inward spiral.

Karpal knew that the calculations needed to test this idea would be horrendous. Dealing with interactions between the strong force and gravity could bring the most powerful computer to its knees, and any software model accurate enough to he trusted would run far slower than real time, making it useless for predictions. The only way to anticipate the fate of Lac G-1 was to try to see where the data itself was heading.

He had the analysis software fit a smooth curve through the neutron stars' declining angular momentum, and extrapolate it into the future. The fall grew faster, gently at first, but it ended in a steep descent. Karpal felt a cool horror wash through him: if this was the ultimate fate of every binary neutron star, it helped make sense of an ancient puzzle. But it was not good news.

For centuries, astronomers had been observing powerful gamma-ray bursts from distant galaxies. If these bursts were due to colliding neutron stars, as suspected, then just before the collision—when the neutron stars were in their closest, fastest orbits—the gravitational waves produced should have been strong enough for TERAGO to pick up over a range of billions of light years. No such waves had ever been detected.

But now it looked as though Lac G-1’s meson jets would succeed in bringing the neutron stars' orbital motion to a dead halt while they were still tens of thousands of kilometers apart. The Catherine wheel’s fireworks, having finally triumphed, would sputter out, and the end wouldn’t be a frenzied spiral after all, but a calm, graceful dive—generating only a fraction as much gravitational radiation.

Then the two mountain-sized star-heavy nuclei would slam straight together, as if there’d never been a hint of centrifugal force to keep them apart. They’d fall right out of each other’s sky—and the heat of the impact would be felt for a thousand light years. Karpal dismissed the image angrily. So far, he had nothing but a three-minute anomaly in an orbital period, and a lot of speculation. What was his judgment worth, after nine years of solitude and far too many cosmic rays? He had to get in touch with colleagues in the asteroid belt, show them the data, and talk through the possibilities calmly.

But if he was right? How long did the fleshers have before Lacerta lit up with gamma rays, six thousand times brighter than the sun?

Karpal checked and re-checked the calculations, fitted curves to different variables, tried every known method of extrapolation.

The answer was the same every time.

Four days.