The Best of Gregory Benford

by David G. Hartwell

  A rattling thump—and they stopped. He felt Patil slam aside the rattling gate. A sullen glow beyond bathed an ornate brass shrine to a Hindu god. They came out into a steepled room of carved rock. Clay felt a breath of slightly cooler air from a cardboard-mouthed conduit nearby.

  “We must force the air down from above.” Patil gestured. “Otherwise this would read well over a hundred and ten Fahrenheit.” He proudly pointed to an ancient battered British thermometer, whose mercury stood at ninety-eight. They trudged through several tunnels, descended another few hundred feet on a ramp, and then followed gleaming railroad tracks. A white bulb every ten meters threw everything into exaggerated relief, shadows stabbing everywhere. A brown cardboard sign proclaimed from the ceiling:

  first ever cosmic ray neutrino interaction recorded here in april 1965

  For over forty years, teams of devoted Indian physicists had labored patiently inside the Kolar gold fields. For half a century, India’s high mountains and deep mines had made important cosmic ray experiments possible with inexpensive instruments. Clay recalled how a joint Anglo-Indian-Japanese team had detected that first neutrino, scooped it from the unending cosmic sleet that penetrated even to this depth. He thought of unsung Indian physicists sweating here, tending the instruments and tracing the myriad sources of background error. Yet they themselves were background for the original purpose of the deep holes: Two narrow cars clunked past, full of chopped stone.

  “Some still work this portion,” Patil’s clear voice cut through the muffled air. “Though I suspect they harvest little.”

  Pushing the rusty cars were four wiry men, so sweaty that the glaring bulbs gave their sliding muscles a hard sheen like living stone. They wore filthy cloths wrapped around their heads, as if they needed protection against the low ceiling rather than the heat. As Clay stumbled on, he felt that there might be truth to this, because he sensed the mass above as a precarious judgment over them all, a sullen presence. Einstein’s crisp distinctions, the clean certainty of the Gedanken experiments, meant nothing in this blurred air.

  They rounded an irregular curve and met a niche neatly cut off by a chainlink fence.

  PROTON STABILITY EXPERIMENT

  TATA INSTITUTE OF FUNDAMENTAL RESEARCH, BOMBAY

  80TH LEVEL HEATHCOTE SHAFT,

  KFG 2300 METERS DEPTH

  These preliminaries done, the experiment itself began abruptly. Clay had expected some assembly rooms, an office, refrigerated ’scope cages. Instead, a few meters ahead the tunnel opened in all directions. They stood before a huge bay roughly cleaved from the brown rock.

  And filling the vast volume was what seemed to be a wall as substantial as the rock itself. It was an iron grid of rusted pipe. The pipes were square, not round, and dwindled into the distance. Each had a dusty seal, a pressure dial, and a number painted in white. Clay estimated them to be at least a hundred feet long. They were stacked Lincoln-log fashion. He walked to the edge of the bay and looked down. Layers of pipe tapered away below to a distant floodlit floor and soared to meet the gray ceiling above. “Enormous,” he said.

  “We expended great effort in scaling up our earlier apparatus,” Singh said enthusiastically.

  “As big as a house.”

  Patil said merrily, “An American house, perhaps. Ours are smaller.”

  A woman’s voice nearby said, “And nothing lives in this iron house, Professor Clay.”

  Clay turned to see a willowy Indian woman regarding him with a wry smile. She seemed to have come out of the shadows, a brown apparition in shorts and a scrupulously white blouse, appearing fullblown where a moment before there had been nothing. Her heavy eyebrows rose in amusement. “Ah, this is Mrs. Buli,” Patil said.

  “I keep matters running here, while my colleagues venture into the world,” she said.

  Clay accepted her coolly offered hand. She gave him one quick, well defined shake and stepped back. “I can assist your assessment, perhaps.”

  “I’ll need all your help,” he said sincerely. The skimpy surroundings already made him wonder if he could do his job at all.

  “Labor we have,” she said. “Equipment, little.”

  “I brought some cross-check programs with me,” he said.

  “Excellent,” Mrs. Buli said. “I shall have several of my graduate students assist you, and of course I offer my full devotion as well.”

  Clay smiled at her antique formality. She led him down a passage into the soft fluorescent glow of a large data-taking room. It was crammed with terminals and a bank of disk drives, all meshed by the usual cable spaghetti. “We keep our computers cooler than our staff, you see,” Mrs. Buli said with a small smile. They went down a ramp, and Clay could feel the rock’s steady heat.

  They came out onto the floor of the cavern. Thick I-beams roofed the stone box. “Over a dozen lives, that was the cost of this excavation,” Singh said.

  “That many?”

  “They attempted to save on the cost of explosives,” Patil said with a stern look.

  “Not that such will matter in the long run,” Singh said mildly. Clay chose not to pursue the point.

  Protective bolts studded the sheer rock, anchoring cross-beams that stabilized the tower of pipes. Scaffolding covered some sections of the black and rusty pile. Blasts of compressed air from the surface a mile above swept down on them from the ceiling, flapping Clay’s shirt.

  Mrs. Buli had to shout, the effort contorting her smooth face. “We obtained the pipes from a government program that attempted to improve the quality of plumbing in the cities. A failure, I fear. But a godsend for us.”

  Patil was pointing out electrical details when the air conduits wheezed into silence. “Hope that’s temporary,” Clay said in the sudden quiet.

  “A minor repair, I am sure,” Patil said.

  “These occur often,” Singh agreed earnestly.

  Clay could already feel prickly sweat oozing from him. He wondered how often they had glitches in the circuitry down here, awash in pressing heat, and how much that could screw up even the best diagnostics.

  Mrs. Buli went on in a lecturer’s singsong. “We hired engineering students, there are many such, an oversupply—to thread a single wire down the bore of each pipe. We sealed each, then welded them together to make lengths of a hundred feet. Then we filled them with argon and linked them with a high-voltage line. We have found that a voltage of 280 khz…”

  Clay nodded, filing away details, noting where her description differed from that of the NSF. The Kolar group had continuously modified their experiment for decades, and this latest enormous expansion was badly documented. Still, the principle was simple. Each pipe was held at high voltage, so that when a charged particle passed through, a spark leaped. A particle’s path was followed by counting the segments of triggered pipes. This mammoth stack of iron was a huge Geiger counter.

  He leaned back, nodding at Buli’s lecture, watching a team of men at the very top. A loud clang rang through the chasm. Sparks showered, burnt orange and blue. The garish plumes silhouetted the welders and sent cascades of sparks down through the lattice of pipes. For an instant Clay imagined he was witnessing cosmic rays sleeting down through the towering house of iron, illuminating it with their short, sputtering lives.

  “—and I am confident that we have seen well over fifty true events,” Mrs. Buli concluded with a jaunty upward tilt of her chin.

  “What?” Clay struggled back from his daydreaming. “That many?”

  She laughed, a high tinkling. “You do not believe!”

  “Well, that is a lot.”

  “Our detecting mass is now larger,” Mrs. Buli said.

  “Last we heard it was five hundred tons,” Clay said carefully. The claims wired to the NSF and the Royal Society had been skimpy on details.

  “That was years ago,” Patil said. “We have redoubled our efforts, as you can see.”

  “Well, to see that many decays, you’d have to have a hell of a lot of observing volume,�
� Clay said doubtfully.

  “We can boast of five thousand tons, Professor Clay,” Mrs. Buli said.

  “Looks it,” Clay said laconically to cover his surprise. It would not do to let them think they could overwhelm him with magnitudes. Question was, did they have the telltale events?

  The cooling air came on with a thump and whoosh. Clay breathed it in deeply, face turned up to the iron house where protons might be dying, and sucked in swarming scents of the parched countryside miles above.

  He knew from the start that there would be no eureka moment. Certainty was the child of tedium.

  He traced the tangled circuitry for two days before he trusted it. “You got to open the sack ’fore I’ll believe there’s a cat in there,” he told Mrs. Buli, and then had to explain that he was joking.

  Then came a three-day trial run, measuring the exact sputter of decay from a known radioactive source. System response was surprisingly good. He found their techniques needlessly Byzantine, but workable. His null checks of the detectors inside the pipes came up goose-egg clean.

  Care was essential. Proton decay was rare. The Grand Unified Theories which had enjoyed such success in predicting new particles had also sounded a somber note through all of physics. Matter was mortal. But not very mortal, compared with the passing flicker of a human lifetime.

  The human body had about 1029 neutrons and protons in it. If only a tiny fraction of them decayed in a human lifetime, the radiation from the disintegration would quickly kill everyone of cancer. The survival of even small life-forms implied that the protons inside each nucleus had to survive an average of nearly a billion billion years.

  So even before the Grand Unified Theories, physicists knew that protons lived long. The acronym for the theories was GUTs, and a decade earlier graduate students like Clay had worn T-shirts with insider jokes like IT TAKES GUTS TO DO PARTICLE PHYSICS. But proving that there was some truth to the lame nerd jests took enormous effort.

  The simplest of the GUTs predicted a proton lifetime of about 1031 years, immensely greater than the limit set by the existence of life. In fact, it was far longer even than the age of the universe, which was only a paltry 2 x 1010 years old.

  One could check this lifetime by taking one proton and watching it for 1031 years. Given the short attention span of humans, it was better to assemble 1031 protons and watch them for a year, hoping one would fizzle. Physicists in the United States, Japan, Italy, and India had done that all through the 1980s and 1990s. And no protons had died.

  Well, the theorists had said, the mathematics must be more complicated. They discarded certain symmetry groups and thrust others forward. The lifetime might be 1032 years, then.

  The favored method of gathering protons was to use those in water. Western physicists carved swimming pools six stories deep in salt mines and eagerly watched for the characteristic blue pulse of dying matter. Detecting longer lifetimes meant waiting longer, which nobody liked, or adding more protons. Digging bigger swimming pools was easy, so attention had turned to the United States and Japan…but still, no protons died. The lifetime exceeded 1032 years.

  The austerity of the 1990s had shut down the ambitious experiments in the West. Few remembered this forlorn experiment in Kolar, wedded to watching the cores of iron rods for the quick spurt of decay. When political difficulties cut off contact, the already beleaguered physicists in the West assumed the Kolar effort had ceased.

  But Kolar was the deepest experiment, less troubled by the hail of cosmic rays that polluted the Western data. Clay came to appreciate that as he scrolled through the myriad event-plots in the Kolar computer cubes. There were 9 x 109 recorded decays of all types. The system rejected obvious garbage events, but there were many subtle enigmas. Theory said that protons died because the quarks that composed them could change their identities. A seemingly capricious alteration of quarky states sent the proton asunder, spitting forth a zoo of fragments. Neutrons were untroubled by this, for in free space they decayed anyway, into a proton and electron. Matter’s end hinged, finally, on the stability of the proton alone.

  Clay saw immediately that the Kolar group had invested years in their software. They had already filtered out thousands of phantom events that imitated true proton decay. There were eighteen ways a proton could die, each with a different signature of spraying light and particle debris.

  The delicate traceries of particle paths were recorded as flashes and sparkles in the house of iron outside. Clay searched through endless graphic printouts, filigrees woven from digital cloth.

  “You will find we have pondered each candidate event,” Mrs. Buli said mildly on the sixth day of Clay’s labors.

  “Yeah, the analysis is sharp,” he said cautiously. He was surprised at the high level of the work but did not want to concede anything yet.

  “If any ambiguity arose, we discarded the case.”

  “I can see that.”

  “Some pions were not detected in the right energy range, so of course we omitted those.”

  “Good.”

  Mrs. Buli leaned over to show him a detail of the cross-checking program, and he caught a heady trace of wildflowers. Her perfume reminded him abruptly that her sari wrapped over warm, ample swells. She had no sagging softness, no self--indulgent bulgings. The long oval of her face and her ample lips conveyed a fragile sensuality…

  He wrenched his attention back to physics and stared hard at the screen. Event vertices were like time-lapse photos of traffic accidents, intersections exploding, screaming into shards. The crystalline mathematical order of physics led to riots of incandescence. And Clay was judge, weighing testimony after the chaos.

  He had insisted on analyzing the several thousand preliminary candidates himself, as a double blind against the Kolar group’s software. After nine days, he had isolated sixty-seven events that looked like the genuine article. Sixty-five of his agreed with Mrs. Buli’s analysis. The two holdouts were close, Clay had to admit.

  “Nearly on the money,” he said reflectively as he stared at the Kolar software’s array.

  “You express such values,” Mrs. Buli said. “Always a financial analogy.”

  “Just a way of speaking.”

  “Still, let us discard the two offending events.”

  “Well, I’d be willing—”

  “No, uh, we consider only the sixty-five.” Her almond eyes gave no hint of slyness.

  “They’re pretty good bets, I’d say.” Her eyebrows arched. “Only a manner of speech.”

  “Then you feel they fit the needs of theory.”

  Her carefully balanced way of phrasing made him lean forward, as if to compensate for his judge’s role. “I’ll have to consider all the other decay modes in detail. Look for really obscure processes that might mimic the real thing.”

  She nodded. “True, there is need to study such.”

  Protons could die from outside causes, too. Wraithlike neutrinos spewed forth by the sun penetrated even here, shattering protons. Murderous muons lumbered through as cosmic rays, plowing furrows of exploding nuclei.

  Still, things looked good. He was surprised at their success, earned by great labor. “I’ll be as quick about it as I can.”

  “We have prepared a radio link that we can use, should the desire come.”

  “Huh? What?”

  “In case you need to reach your colleagues in America.”

  “Ah, yes.”

  To announce the result, he saw. To get the word out. But why the rush?

  It occurred to him that they might doubt whether he himself would get out at all.

  They slept each night in a clutch of tin lean-tos that cowered down a raw ravine. Laborers from the mine had slept there in better days, and the physicists had gotten the plumbing to work for an hour each night. The men slept in a long shed, but gave Clay a small wooden shack. He ate thin, mealy gruel with them each evening, carefully dropping purification tablets in his water, and was rewarded with untroubled bowels. He lost weigh
t in the heat of the mine, but the nights were cool and the breezes that came then were soft with moisture. The fifth evening, as they sat around a potbellied iron stove in the men’s shed, Patil pointed to a distant corrugated metal hut and said, “There we have concealed a satellite dish. We can knock away the roof and transmit, if you like.”

  Clay brightened. “Can I call home?”

  “If need be.”

  Something in Patil’s tone told him a frivolous purpose was not going to receive their cooperation. “Maybe tomorrow?”

  “Perhaps. We must be sure that the devotees do not see us reveal it.”

  “They think we’re laborers?”

  “So we have convinced them, I believe.”

  “And me?”

  “You would do well to stay inside.”

  “Um. Look, got anything to drink?”

  Patil frowned. “Has the water pipe stopped giving?”

  “No, I mean, you know—a drink. Gin and tonic, wasn’t that what the Brits preferred?”

  “Alcohol is the devil’s urine,” Patil said precisely.

  “It won’t scramble my brains.”

  “Who can be sure? The mind is a tentative instrument.”

  “You don’t want any suspicion that I’m unreliable, that it?”

  “No, of course not,” Singh broke in anxiously.

  “Needn’t worry,” Clay muttered. The heat below and the long hours of tedious work were wearing him down. “I’ll be gone soon’s I can get things wrapped up.”

  “You agree that we are seeing the decays?”

  “Let’s say things’re looking better.”