Part 2 (1/2)

His talk had been about the energetic jets that shoot out from the disks around black holes, a recurring hot topic in the field. As new windows opened for telescopes across the electromagnetic spectrum, the jets showed more detail, fresh mysteries.

In his talk he had used the entire modern a.r.s.enal of theoretical attack: calculations, computer simulations, and finally, to truly convince, some easily digested cartoons. n.o.body really felt that they understood something unless they carried away a picture of how it worked. ”Get it right in the 'cartoon approximation' and all else follows,” his thesis adviser had sagely said.

Benjamin had shown that the jets were very probably confined by their own magnetic fields. This could only be so if they carried a net current out from their source, presumably a large black hole and its churning neighborhood. He had ended up with a simple declaration: ”That is, in a sense the flows are self-organized.” In other words, they neatly knit themselves up.

Then the knife question came from a figure Benjamin did not know, an angular face halfway back in the rows of chairs. Benjamin felt that he should know the face, there was something familiar about it, but there was no time to wonder about ident.i.ty now. A quick riposte to an attack was essential in the brisk world of international astrophysics. Ideas had their moment in the sun, and if the glare revealed a blemish, they were banished.

The question subtly undermined his idea. In a slightly nasal Brit accent, the voice recalled that jets were probably born near the disk of matter rotating about black holes, but after that were at the mercy of the elements as they propagated outward, into the surrounding galaxy.

Smoothly the questioner pointed out that other ways to confine and shape the jets were easily imagined-for example, the pressure of the galaxy's own gas and dust-and ”seemed more plausible, I should imagine.” This last stab was within the allowed range of rebukes.

Benjamin took a second to a.s.sume an almost exaggerated pose of being at ease, putting his hands in his pockets and rocking back on one foot, letting the other foot rise, balanced on its heel. ”Lack of imagination is not really an argument, is it?” he said mildly.

A gratifying ripple of laughter washed through the room. Those already half out of their seats paused, sensing a fight. Benjamin quickly went on, catching the momentum of the moment. ”To collar a jet and make it run straight demands something special about the medium around it, some design on its part. But if the jet is self-managed, right from the moment it was born, back on the accretion disk-that solves the confinement problem.”

Nods, murmurs. His opponent cast a shrewd look and again Benjamin could almost place that face, the clipped, precise English accent. The man said casually, ”But you have no way of knowing if a disk will emit that much current. And as well, I should think that no relativistically exact result could tell you that in general.” A smirk danced at the edges of the man's mouth. ”And you do realize that the black hole region must be treated in accordance with general general relativity, not merely relativity, not merely special special relativity?” relativity?”

The audience had turned to hear this, eyes casting back, and Benjamin knew that this was somebody important. The shot about relativity was a clear put-down, questioning his credentials. A nasty insinuation to make about a fresh Ph.D., the ink barely dry on his diploma. He drew in a long breath and time slowed, the way it does in a traffic accident, and suddenly he realized that he was frightened.

His was the second colloquium of the academic year, a prestigious spot in itself. The Astronomy Department liked to get the year off with a bang, featuring bold, invigorating topics. The air was crisp with autumn smells, the campus alive with edgy expectation, and Channing was in the tenth row in her blue good-luck sweater.

Act. Say something. But what?

He caught her eyes on him and stepped forward, putting his hands behind his back in a cla.s.sic pontifical pose, the way he had seen others signal that they were being thoughtful. In fact, he did not need to think, for the answer came to him out of nowhere, slipping into words as he began a sentence, not quite knowing where it was going.

”The disk dynamo has to give off a critical level of current,” he said easily, getting the tone of bemused thought. ”Otherwise it would not be able to coherently rotate.”

He let the sentence hang in air. The senior figures in the department were watching him, waiting for further explanation, and he opened his mouth to give it. His nostrils flared and he saw with crystalline clarity that he should say nothing, leave the tantalizing sentence to sink in. Bait. This guy in the back was a Brit, dish out some of his own style to him.

He had gotten everyone's attention and now the audience sensed something, heads swiveling to watch the Englishman. Stand pat? No Stand pat? No.

Benjamin decided to raise the stakes. A cool thrill ran through him as he added, ”I would think that was physically clear.”

Half the audience had already turned toward the back rows and when he spoke they quickly glanced around like a crowd at a tennis match following a fast volley.

The face in the back clouded, scowling, and then seemed to decide to challenge. ”I should think that unlikely” came the drawl, lifting at the last word into a derisive lilt, un-like-ly un-like-ly.

Benjamin felt a p.r.i.c.kly rush sweep over him. Gotcha Gotcha.

”It follows directly from a conservation theorem,” Benjamin said smoothly, savoring the line, striding to the overhead projector and slapping down a fresh viewgraph. He had not shown it in the talk because it was an arcane bit of mathematics, not the sort of thing to snag the attention of this crowd. No eye-catching graphics or dazzling data-crunching, just some lines of equations with double-integral signs, ripe with vector arrows over the symbols. A yawner-until now.

”Starting with Maxwell's equations,” he began, pointing, then glanced up. ”Which we know to be relativistically correct, yes?”

This jibe made a few of the theorists chuckle; everybody had learned this as undergraduates, but most had forgotten it long ago.

”So performing the integrals over a cylindrical volume...” He went through the steps quickly, knowing that n.o.body this late in the hour wanted to sit through five minutes of tedious calculations. The cat was out of the bag, anyway. Springing a crisp new viewgraph-and then two more to finish the argument, all tightly reasoned mathematics-tipped his hand. He had antic.i.p.ated this question and prepared, deliberately left a hole in his argument. Or so the guy in the back would think-was thinking, from the deepening frown Benjamin saw now on the distant, narrow face-and knew that he had stepped into a trap. thinking, from the deepening frown Benjamin saw now on the distant, narrow face-and knew that he had stepped into a trap.

Only it wasn't so. Benjamin had not really intended it that way, had left the three viewgraphs out because they seemed a minor digression of little interest to the hard-nosed astrophysicists who made up most of the audience.

”So we can see that this minimum level is quite enough to later on confine the jets, keep them pointing straight, solve the problem.” He added this last little boast and stepped back.

The Brit face at the back curled up a lip, squinted eyes, but said nothing. A long moment pa.s.sed as the colloquium chairman peered toward the back, rocking forward a little, and then saw that there would be no reply. Game, point, match Game, point, match, Benjamin thought, breathing in deeply of air that seemed cool and sharp.

There were two more questions, minor stuff about possible implications, easy to get through. In fact, he let himself strut a little. He expanded on some work he contemplated doing in the near future, once he and Channing had the wedding business over with and he could think, plan the next step in his career. He felt that he could get away with a slight, permissible brag.

Then it was over, the ritual incantation from the chairman, ”There is wine and cheese in the usual place, to which you are all invited. Let us thank our speaker again...”

This applause was scattered and listless, as usual as everybody got up, and the crowd left. His major professor appeared at his elbow and said, ”You handled that very well.”

”Uh, thanks. Who is that guy?” Benjamin glanced at the crowd, not letting any concern into his face.

”Dart. Kingsley Dart.”

”The similarity solutions guy from Oxford?”

”Right. Just blew in yesterday afternoon, visiting for a few days. Thought you had met him.”

”I was squirreled away making viewgraphs.”

”You sure nailed Dart with those last three.”

”I hadn't really planned it that way-”

An amused grin. ”Oh, sure.”

”I didn't!”

”n.o.body gets timing like that without setting it up.”

”Well, my Benjamin did,” Channing said, slipping an arm around his. ”I know, because he had them in the very first version of the talk.”

Benjamin smiled. ”And you told me to drop them.”

”It worked perfectly, didn't it?” she said, all innocence.

He laughed, liking the feeling of release it brought, liking that she had made him seem a lot more the savvy Machiavellian than he was, liking the whole d.a.m.ned thing so much it clutched at his heart somehow in the frozen moment of triumph. Off to the side two of the big names of the department were talking about the implications of his work and he liked the sound of that, too, his name wafting pleasantly in the nearly empty room. He could smell the aging, polished wood, the astringent solvent reek of the dry markers from the blackboard, a moist gathering in the cloying air of late afternoon. Channing kept her arm in his and walked proudly beside him up the two flights to the wine and cheese.

”You were great great.” She looked up at him seriously and he saw that she had feared for him in this last hour. Berkeley was notorious for cutting criticisms, arch comments, savage seminars that dissected years of research in minutes of coldly delivered condemnation.

She had kept close to him through the aftermath, when white-haired savants of the field came up to him, holding plastic gla.s.ses of an indifferent red wine, and probed him on details, implications, even gossip. Treating him like a member of the club, a colleague at last. She had tugged at his arm and nodded when Dart came into view, earnestly talking to a grand old observing astronomer. Dart had a way of skating over a crowd, dipping in where he wanted, like a hummingbird seeking the sweet bulbs. Eventually he worked his way around to Benjamin, lifting eyebrows as he approached, his face in fact running through the entire suite of ironic messages, very Euro, before shooting out a hand and saying, ”Kingsley Dart. Liked the talk.”

Firm handshake. ”You seemed to disagree with most of it.”

A shrug. ”Testing the ideas, just testing.”