Boundary

by Eric Flint

  "I think you will be more than satisfied with the challenge and the subject matter, A.J."

  When they reached the cases, Helen picked up one of them. It was startlingly heavy, but Helen set her jaw and forced herself to carry it as though it wasn't any heavier than she'd expected. She wasn't sure why. Habit, she supposed, of never showing weakness in a profession that was still mostly male-dominated.

  By the time they reached the dig area, her arm felt like it was about to pull out of its socket and she was cursing her perverse pride.

  Then she caught A.J. grinning at her.

  "You know, I usually get help carrying that one, ma'am."

  "Then why didn't you offer any, you twit?" Joe demanded.

  "She seemed to want to handle it. Who am I to tell her otherwise?"

  With a groan of relief Helen put the case down. "Just what is in there?"

  "Fuel-cell generator. Some of the gadgets I'm going to use need some pretty high-power juice, and I knew this dig wasn't exactly going to have electric outlets handy. Now, you just give me some peace and quiet to set up and test some stuff, and I'll be able to get started."

  Helen indicated a tarp and field tent nearby. "We set one up for you near the site. You'll need us to show you what to do, right?"

  "Certainly. I'm no paleontologist. I need to see what you need done, and you'll probably have to give me feedback on the data, so I can refine it to what you really need."

  Helen caught a faint glint of color from behind the mirrored glasses as he entered the darker area of the tent. She realized that A.J. must be using a VRD or projective display on or from his glasses.

  "I'll give you a holler when I'm ready."

  They spent the next hour or so making sure the site was cleared of anything that might interfere with A.J. Baker's work—tools, canvas coverings, they even swept away dust. Finally Helen heard a call from the tent. She went over, with Jackie and Joe following.

  "You're ready, A.J.?"

  "Ready to work my magic, yes, indeed." A.J. turned. To Helen's astonishment, there appeared to be a literal halo of light hovering around the man's head. A gasp from Jackie confirmed it was not her imagination.

  "Oh, for the love of—A.J., you showoff!" Joe snorted. "And there's no way it should be a halo, anyway. Why not horns?"

  "How do you do that?" Jackie demanded.

  A.J. patted the large pouch on his belt. "Fairy Dust. From Dust-Storm Tech. Finest intelligent dust sensor motes on the planet. These are integrated with micromotile units to let them fly, as long as I can either keep' em supplied with enough power to scavenge—or I'm willing to let them drain the hell out of the onboard batteries for the sake of a few seconds of showing off. Yeah, that's a cheap stunt using their illuminators, but it's fun."

  He opened the flap. The halo, which at closer range appeared to be made up of hundreds or even thousands of individual tiny sparks of light, poured itself into the pouch.

  "These things aren't toys, though. It's the heart of my approach. Thousands of ultrasensitive sensors all over the survey area, networking themselves together automatically, then using all that data to pull out a really detailed picture of whatever lies below. The trick is knowing what sensors and modalities to use and how to combine them and process the data the right way. Now, let's take a look at this dig of yours."

  As they headed to the dig area, Jackie glanced at the belt pouch curiously. "I've heard of them being used for things like inventory tracking and so on, but . . ."

  "That's just the tip of the iceberg," A.J. said. "Even back in the first decade of this century, when Dust, Incorporated, Ember, and a few others first started making intelligent sensor motes, it was clear there were a lot of potential uses for distributed sensor and computing networks that were embodied as near-microscopic motes that each had their own power, communication, computation, sensor, and memory capacity. I honestly don't think I could list every use I've thought of for these things in the past few years."

  "So these motes can look right through the rock?"

  A.J. laughed. "Not exactly. Let me take a look at what we have and I'll explain a little more."

  Helen showed him around the dig area, letting the imaging and sensor expert kneel down to examine the fossils and surrounding rock. She saw him reach into the pouch and then let fall a ghostly shimmer of the dust-mote sensors across the area. From the side, Helen could see that the light behind his glasses was directed into his eye; what she'd seen vaguely before was the reflection. A Virtual Retinal Display, then, rather than a mini heads-up display projection. The VRD flickered brightly from his eye for a moment or two.

  "Hmm, interesting." The imaging specialist seemed to have the habit of talking to himself. "Yeah, we can work with that."

  He turned back to Jackie. "The motes are really excellent at sensing things, and if I combine the signals from thousands of them across the area, that's great—but only if there's something to sense. And there's no way anything their size can produce the beefy signals I'm going to need. Penetration through rock depends on a lot of different things—the type of signal, the wavelength, the precise type of rock, presence of moisture, and the power available probably being the most dominant, although there's a bunch of other ancillary ones. For the most part, I can control three of those variables—type, wavelength, and power. The trick here is that we have something of a dilemma. We want lots of penetration, but we also want lots of detail. As a rule, penetration increases with increasing wavelength—but the level of detail that can be detected decreases with increasing wavelength. If I want a shorter wavelength to give me a readable return, then I need a lot of power."

  Helen nodded along with Jackie, as A.J. continued to carefully sift his Fairy Dust onto the ground in the area of the fossils and the rock still left to be removed.

  "So what do you use? GPR? Seismics?"

  "The short answer is yes." A.J. grinned. "Ground Penetrating Radar is just fine, for some things. But for others, some acoustic signals are good. Seismic shock is related to acoustics, of course, but I can induce different signal characteristics with acoustics than with a simple seismic signal. I can also sometimes get results with powerful magnetic fields. They react with the metals in the ground and bones, and bones are often packed with metal compared to their surroundings. I also use radiation detection—as I'm sure you know, sometimes fossils accumulate significant radioactives."

  Helen nodded.

  "There have been times I've used radiation directly in imaging, but that's not really practical in this setting, so I'll have to settle for whatever I get on the passives. Straight centimeter-scale radio waves on as high power as I can manage is another thing I'm going to try. While that wouldn't normally penetrate very far, a lot of your fossils here aren't all that far below the surface. I also try to use digital pulses where possible."

  "Does that make them penetrate farther?" Helen asked. It didn't seem likely to her.

  A.J. shook his head, smiling in acknowledgement of her doubtful tone. "Not directly, no. But what it does do is make it much, much easier for me to pick up the return signal from the noise, because I can listen for a specific pattern. I know what I'm looking for, in essence, and that really increases the chances of picking it up. Where the motes come in is in registering the returns from all different modes in thousands of closely related vectors, which the sensor net can coordinate and extract as precise survey points in spacetime. The motes construct their own ad hoc network and then derive their own relative positions with very high accuracy. Between time-of-flight, multiple triangulation, and a few other tricks like performing interference patterns, the network characterizes itself to within very small fractions of an inch. This means that the combined received signals are known to an extremely high degree of accuracy. That takes some processing time—that's what it's doing now, since I've stopped playing Tinkerbell.

  "So once the network's fully characterized, I start setting off the signal pulses. I let the network know"—he tapped his gl
asses and the virtual control interface that only he could see—"exactly what signal I'm about to send, then trigger it. The net records all the responses it can, I hit it with another pulse; maybe change modes, it starts building up a rough picture. I examine it, see if I've got something coming up. Maybe I go back, do a few more GPR or radio shots, or try another acoustic signal, or shift frequencies. Eventually, I've got all the data I think will be useful. Then I can really go to town on this stuff; sensor fusion, bandpass filtering, synthetic aperture, Kalman and Weiner filters, all that kind of thing, plus some tricks of my own.

  "With a handful of these motes and no special signal generators, I can use the ambient sound to locate and determine the number, direction, and general composition of your tents—without any of my dust motes actually touching the tents. Heck, with equipment twenty years older, I could send any two of you off to have a conversation, and not only locate you, but pick out your entire conversation, whispered, on the other side of a hill three hundred meters off. These motes have access to my own neural net code, expert systems, fuzzy logic structures, all sorts of stuff in the control unit and local heavy-duty processors, like in the main control unit here."

  He patted another simple metallic box on his belt. "Give me powerful signal sources, and I'll guarantee to map out anything you want, above or below ground. And in this case, I'll even guarantee that you'll have enough detail to count teeth in a skull."

  "Can you keep a record of how you produce the results?" Helen asked.

  "Not only can I," A.J. answered, pacing out the area again as though measuring it, "it's pretty much part and parcel of the process—nice alliteration there, huh? I keep the raw data and track the sequence of filtering and analysis, all the way in. I have to—sometimes you don't get the best results and you need to experiment by taking out one step, moving it to another point in the sequence, and so on. It can make a big, big difference in the final results whether you filter first and then run an enhancement process, or enhance first and then filter, for instance. Pillage, then burn, so to speak."

  He stopped, nodded to himself, then turned back towards the tents. "Well, it's getting pretty dark out here, but rather than waste time, I'll just get started."

  Jackie and Helen held the lights as A.J. unpacked a number of devices with thick, rugged power leads.

  As he did so, Helen studied him, a bit surreptitiously. Somewhat to her surprise, she was starting to find the man interesting.

  In many ways, A.J. Baker was obviously a classic geek. Who else got that enthusiastic about dry-as-dust technical matter? But the muscles visible in his arms when he hefted the first case—the one that had nearly pulled Helen's shoulder out of its socket—made it clear that A.J. was in far better physical condition than the average geek.

  On a personal level, the muscles impressed Helen even less than the flamboyantly awkward geeky mannerisms. But she found the combination rather intriguing. It reminded her of . . .

  Well, herself, actually.

  Since Helen didn't have that damnable male ego to deal with— the one that crucified every high school geek in existence—her own mannerisms weren't as awkward as A.J.'s. At least, she hoped not. But she could get just as enthusiastic when discussing paleontological issues, which were often literally as dry as dust. And on the few occasions when she ventured into public gymnasiums for a workout, she usually got admiring looks from all the men present and envious ones from the women. Even from women half her age.

  From men half her age, she always got admiring looks. Ogles, often enough, to call things by their right name.

  The thought of young men rallied her. Stop this, woman. He must be fifteen years younger than you are.

  Thus fortified, Helen went back to studying A.J. from the perspective of an expert in one field watching another at his own. She did her best to ignore the treacherous little voice at the back of her mind, as it worked its way through simple mathematics.

  Don't be silly. He's not as young as he looks. Can't be, not even in his cutting-edge field. He's got to be at least twenty-five or twenty-six. Maybe twenty-seven. Subtracted from thirty-eight, that is not fifteen years younger. It's only eleven. Maybe even less.

  Shut up.

  "Okay, here we got your GPR unit." A.J. held up a wide metallic antenna unit, followed by a cylindrical object that looked like a solid rod of metal but probably wasn't. "And this here's the impactor for seismic signals, some electromagnetic pulsers—keep metal and electronics that aren't shielded well away, folks—and my own shriekers. High-power ultrasonic pulsers."

  The "shriekers" were strange things, looking a bit like large versions of the paddles found on a defibrillator unit, but ending with quivering blobs that looked like nothing so much as firm blue jello. They were labeled Kaled 1 and Kaled 2.

  "What's that stuff?" Jackie asked, pointing to the blue blobs.

  "Couplant gel. The attenuation of the signal through air is something fierce, so you try to use couplant to bring it more directly to the target. I wash the area off with a high-pressure water jet, then push the gel up against the rock. That increases the efficiency by many times. Even so, it'd be just plain useless without the Fairy Dust. You can immerse a sample in liquid and get good results, but in the field you just wouldn't get the penetration needed. With the sensor motes properly programmed and all over the place, and digitized pulses for signature return filtering, I can get results out of returns almost a hundred times weaker than I could with normal sensors."

  "Anything else we can do to help?" Helen put in, seeing that he was now laying out his devices in a carefully planned order.

  "Yeah," A.J. said. "Go away. Meaning no offense, just that once I start taking the readings the more people and objects in the area, the harder it's going to be for me to compensate for the signals. I have to sit dead still while the data's being gathered, and even so I'll probably be having an effect that I'll notice later."

  "No problem, we understand." Helen and Jackie started off. "Let us know when you're done."

  "Sure thing," A.J. replied absently, already staring at a display on his VRD unit. "Your problems are just about over."

  Chapter 4

  "What the hell is that?"

  A.J. was taken aback by the vehemence of Helen's question. "Hey, cool down. And why are you asking me? You're the paleontologist. I just image what's there."

  Joe shook his head, then bent down to A.J. and spoke quietly. "Look, I don't know what you think you're doing, but cut out the joking and give us the real data."

  A.J.'s eyes narrowed. "That is the real data. Top of the line. Imaged in three different spectra, multiple wavelengths, filtered, neural-net-processed, compared with known data for verisimilitude, and data-fused and analyzed out the wazoo. If I wasn't doing this for you and my own entertainment, you'd be paying about a hundred grand for this little job—over and above expenses. That is exactly, precisely, and inarguably what is down there."

  "But that's just . . . impossible," Joe said defensively. He gestured at the projected image before them.

  The computer-enhanced graphic showed the entire dig area in three-dimensional, mostly pastel false color. The rock still to be removed was present as an outline, an overlay of faintly gray glass. The fossils of the three raptors were clearly visible, the two newer ones now fully visible in their curved death poses. In addition, two more raptor skeletons were revealed, one on either side of the other three, making a rough three-quarter circle around the perimeter of the dig area. All five skeletons were fully articulated, possibly the finest specimens of Deinonychus ever uncovered— and all of them were sitting on a stippled red and purple layer that was the K-T boundary itself. White dots showed the position of hundreds of the strange pebbles, both around and past the raptor skeletons.

  But it was what squatted ominously in the center of the image, in the middle of the rough circle delineated by the fossilized predators, that was the focus of such utter disbelief. It was large—close to four meters long, from
end to end—and was as clearly defined as the other skeletons. The problem was . . .