Chapter One

The engines had stopped after the bright flash. The ship, still moving, drifted away from the asteroid where the light had originated. Inside the cabin, two badly shaken humans sat bolt upright in the pilot and copilot's chairs, numb and frightened.

"Meu Deus! What just happened?" Zelle asked.

"I don't know!" Mak replied. "Engines aren't responding." He pressed buttons on his console. There was a muted click from somewhere and lights came on. "We have emergency lights, but they're battery powered. That flash probably took out our reactor. If I can restart it, the engines may work, but I don't know..."

Mak paused while he tried to reset the remaining switches. "Instruments are dead. Nothing from inside, all readouts are offline, nothing from the external sensors either. The visible band 'scope is working, probably because it's not electronic except for the tracking system. Which means it's almost useless."

"That's bad," muttered Zelle, pressing sensitive areas on the touchscreen that stubbornly refused to work. "Whatever hit us is still out there!"

"Yes, but unless that asteroid has a drive system..." Mak thought for a moment. "No, the neutrino sensors would have detected anything that powerful before we got close. The damage is probably done, but the drive system's not the worst part. Notice how quiet it is? The fans aren't circulating the air, which means life support is off-line. Not surprising, since it looks like everything that's not backed up by batteries shut down when the reactor kicked off.

"So, no life support. I estimate we have enough air, water, and food for maybe two weeks if we cut back on usage," Mak continued. "And I can't even be sure of the time estimate. No instruments, so I'm going by what I remember. Air is the most critical. We can go without eating, at least for a while, but we can't stop breathing. The good news is that the oxygen tanks are full. The matter converter keeps them topped off and I would have noticed if that wasn't happening.

"Not sure how much hydrogen is available, though; the scoops were running, but so were the engines. Figure at least 75% H-two capacity in onboard storage. So I've got fuel, if I can figure how to use it, but the active carbon dioxide scrubbers won't work without power. The passive ones were never intended to be more than an emergency backup in case the active system needed repairs, so as soon as they're saturated..." Mak's voice trailed off. He'd said all that needed to be said.

"But you got a full set of memory implants before we left. You can fix the reactor, can't you?" asked Zelle, his concern obvious.

"I got the implants, but they're not very useful because there was no time to integrate them with my other memories. Central said it would take at least a month to sort everything out, and anyway, even if I had full usable memory, getting the reactor back online depends on how bad it was damaged. I may not be able to restart it. For all I know, it may have been slagged beyond repair. It's frustrating. Some things I remember, but others that should be in my memories just aren't there.

"Change that; they're probably there if I can just find them." Mak chuckled bitterly. "Old people used to have that problem. The older they got, the worse their memories got. Everything was still in there somewhere, but the connections to find the memories were missing and I haven't even made my connections yet! Integration would have taken at least a month and we were in a hurry to leave.

"Now, I just don't know. There may not be time enough to locate what I need. Always assuming the information was part of the implant and that the fix is fairly simple. What if I don't have the necessary tools or spare parts?"

"Yes, I see what you mean. But it all starts with your memory, so if you can't integrate the downloads into usable memory within two weeks...?"

"We'll die out here," agreed Mak. "But here's the thing, my brain and the chip are constantly working on the implanted memories. There's nothing I can do to hurry the process, but if I concentrate on what I remember about the life support system, that may be enough to influence which memories are integrated first.

"Considering our needs in order, survival is our priority. Not just short-term survival, because we don't know how long we'll be out here. It could take months to limp back and the passive scrubbers won't last that long. Meaning that I've got to get the active system going. Not just to remove the carbon dioxide, but to split the molecules. We've got to have the oxygen. What's in the onboard tanks won't last more than two weeks, roughly as long as the passive filters.

"Here's the problem, I can use the chemical filters to take out the CO² and replace it with stored oxygen, but the chemicals in the filters can't be reused unless I run them through the matter converter. Which almost certainly isn't working right now. No electricity, except for the batteries, and that's not enough to even start the MC. Got to have juice to generate the containment fields, and even fully charged, the batteries don't have it. The atmosphere pumps also require electrical power, but I might be able to do something about that. And maybe...even if the power plant isn't putting out at 100%, I might be able to get it to provide enough juice to run the pumps and the matter converter."

Mak paused while he tried to remember." There may be a workaround. There's an auxiliary generator; it's normally used to restart the reactor after a shutdown. It might provide enough power to run the atmosphere pumps and keep the cabin warm, but I don't know because that's part of what I can't remember.

"Just to start with, I would have to convert the automatic controls to manual and switch the generator's output over to life support. I know how to do that, but I'm not sure the aux gen puts out enough power to run life support and the matter converter at the same time. The converter's internal fields draw a lot of power in the beginning, although some of the startup power is recaptured later on. I may have to alternate between it and life support, but I can probably do that and if I can, it will keep us alive.

"Full engine power, no way. Right now, we're dead in space but I may be able to use the steering engines to slow us down. Our orbit will decay, so we'll drift sunward. If we can survive long enough to reach Earth's orbit or at least get closer, I might be able to call for help. But out here, considering how much background noise I'd need to punch through? We're on our own."

"Lots of 'maybes', 'might's, and 'I don't knows', Mak. But I understand that you're doing the best you can. We just have to hope you locate those memories. Two weeks, reduced activity," Zelle mused. "I sure hope your brain understands the necessity of finding those memories! And from now on, we don't lift off until someone on board knows how to fix things!"

"Not to mention figure out why an uninhabited asteroid would flash us with some sort of weapon! And how that flash managed to kick our reactor off-line. We were fine until that happened," Mak observed.

"Yes. You work on remembering what you don't know, I'll see if I can come up with a rational explanation for what happened. My people do a lot more traveling in space, but my knowledge may not help because our rocket-powered ships aren't even in the same class as this one. I'm pretty sure we haven't got around to exploring the asteroid belt. But in this dimension..." Zelle shrugged. "There's no telling what might have happened. A previous expedition from your Prime could have left some sort of automated device. That bright light bothers me; the raiders that grabbed our dimension shuttle used bright flashes too. They could have been working out here."

"Lasers, most likely," Mak said, thinking aloud. "We know about them, but we don't use ours as weapons. Industrial applications mainly, according to my chip. But if that's what happened, if we got hit by a laser, we're lucky it didn't do more damage."

"It could still kill us," responded Zelle, "depending on whether you get the reactor started. But fortunately for us, your ships have ceramic hulls. This one may be able to shrug off a hit that would have blown a hole through our rocket-propelled ships."

"It survived some of the damage. We're still alive; all it did was kick the reactor offline. Whether it also caused some sort of flashback that damaged critical reactor parts..."

***

Ten days later, Mak's efforts paid off. The lights brightened and the air pump's murmur, something they'd never noticed until it stopped, broke the silence. The screen illuminated, displaying the readouts from the emergency battery pack and internal sensors. Recharging would take two hours and twelve minutes; the batteries had dropped to 38 percent of capacity.

"Reduced power output from the auxiliary generator, but it may be enough," reported Mak. "Even when it's working at max capacity, it puts out less than 5% of what the fusion plant does. The matter converter will operate, but it won't be anywhere close to 100% either. Not enough power available.

"I had to dial back the MC's input draw to keep from blowing the aux gen. There's not enough power for the strong EM fields needed for nuclear synthesis, but there's enough to split the carbon dioxide molecules. Which means we'll have oxygen and food--make that something edible--by hydrating the excess carbon. I doubt we'll like it. According to my chip, it tastes like burned toast. Calories, yes; we'll have enough to keep us alive for about a year, but no gourmet meals.

"And maybe not enough vitamins to keep us healthy, but it won't taste like poop. A good thing, because the MC recycles that too. Bottom line, there's enough power to split chemical bonds but not to rework nuclei. Hydrating carbon's a simple chemical reaction that requires comparatively little energy.

"The scoops that collect hydrogen for the engines, make that the generators that create the fields that scoop up hydrogen, are fried. That's where that faint burned smell is coming from. Most likely, that bright flash overloaded the fields and caused a flashback. The scoop-field generators will have to be replaced when we get home, but until then the only hydrogen we have is what's in the tanks.

"There's a workaround for that too, not a good one, but something. I'll divert some of the waste carbon from the MC to the steering engines. And that's the ultimate time limit for survival; we're burning next year's food to provide thrust. Here's the sequence; the steering impellers, life support, and the matter converter require electricity. Everything depends on the auxiliary generator, which won't work without fuel. We don't have nearly enough hydrogen, but carbon will work. At least for a while. Eventually, it will clog the aux gen's injectors.

"Of course, if I had full power the MC could convert the carbon to hydrogen, but I don't. Not only don't I have enough to run the MC at full power, I've got to apportion the generator's output! Life support has to run almost continuously, the matter converter has to run periodically, and only after it's switched off will I have power for the steering engines. And we won't get much boost because of the reduced power, tenth of a gee acceleration at most. I'll keep working on the reactor, but I have no idea whether I can restart it. The way I see it, we've got one chance only; we slow down, coast toward home, and hope for the best.

"And even if we do manage to reach Earth's orbit, maybe even when the Earth is on this side instead of the other side of the sun, we can't land. The steering engines aren't strong enough. But I think I can get the radios online; I remember that much. Maybe even get the telemetry link transmitting. If Central hears us, it will notify someone to send help. We'll also need some sort of beacon so the rescue ship can find us, but that part I haven't figured out yet."

"How long to reach Earth's orbit, Mak?"

"At least six months, depending on when Central picks up our signals. Right now, Earth Prime is heading away from us and we probably won't be able to catch up. And if they don't send help within a year, it won't matter. It's gonna be a boring trip, except for wondering if we'll last long enough to get there."

"Do you play chess?" asked Zelle innocently.

"No. I never learned," admitted Mak. "Different kind of games on Prime."

"Don't worry, I'll teach you!"

 

Chapter Two

Things had changed on Darwin. The danger was still there, but distant; no longer the wilderness experience that Matt and the others had faced, it was now roughly similar to what early trappers had faced when they pushed into the American west.

The transplants concern now was to how best to manage their planet. To this end, rules had been adopted. Development would be limited; the first rule for any endeavor was to not harm the local biosphere beyond tolerance. There would be no smog, no rivers that caught fire, no dead streams or lakes. There would also be no extinction of plants or animals due to human encroachment. People would live with, and be part of, the biosphere.

Those who ignored the new rules, who believed that the rule-makers had no jurisdiction, soon found out differently. The lessons were painful, sometimes fatal. Darwinites had little patience for the uncooperative.

***

Francisco, Bear, and Colin were sampling the latest dish from New Home's kitchens.

"Different," Francisco said.

"Sweet, but kind of spicy," Bear observed.

"I'll have a talk with the cooks. That one's off the menu," agreed Colin. "The spices smelled good, although considering the taste, 'spice' might not be the right word." The three grinned at each other and by mutual agreement, set aside the dishes holding the cook's latest attempt to create a grape-based pie sweetened with honey. Plus sage, and more than a hint of juniper that lingered unpleasantly after the sweetness was gone.

"Matt's asking a lot of us," Bear said.

"Yeah, but I'm not sure he understands. That jumper of his makes getting around easy. To my way of thinking, it's too easy," Colin said. "I'll use the one he gave me to save lives, but otherwise I'll leave it parked."

"The rifles are tempting too," Francisco agreed. "I know Matt said we're not to use them unless we're invaded, but what if someone decides we ought to thin out the dire wolves?"

"Some of our knuckleheads are arguing we do just that," Bear said, "because they're too dangerous. Their argument is that you can kill individual wolves, but not a large pack."

"Unless you have a rifle! Then it's fifty shots without reloading," Francisco pointed out. "No pack is that large."

"Yeah. They don't understand; if we let all that technology get loose, it's bound to change things," said Colin. "Old Earth couldn't control it and I doubt we can either. We didn't have any of that stuff when we got here, so we had to figure things out. But as soon as you start depending on tech, you don't need to think. Use a jumper to locate the wolfpack, then start shooting. Fifteen minutes, tops; no more dire wolves, not in that pack. And within a month, no wolfpacks."

"And no more Darwin's World," Bear said. "If we start shooting wolves from the air, others will too."

"And then the bison will multiply, unchecked," Colin agreed. "They'll eat the prairie grasses down to the roots, and after that they'll starve. And when that happens, we'll go hungry too. Technology will change things if we let it, and then we'll go down the same dark hole Old Earth did."

"I don't like the wolves," Bear said, "They almost got me a year ago. But they keep things in balance." He got up from the table and brought back a pitcher of ale and three mugs.

"That's a new batch," said Colin. "We added a few tiny cone-like things we think are hops, or will be after a few generations! They're not poison, and to be honest I like the bitter taste. Let me know what you think of it." He took a deep drink of the frothing brew and smacked his lips appreciatively.

Following his lead, the other men drank deep.

"Pretty good," opined Francisco. "Takes away the aftertaste of that pie!" The three chuckled at that comment.

***

The three had much in common; each was the leader or co-leader of a village.

Home had been first, built near the river as soon as they arrived. To house the tribesmen who had made the trek; no one anticipated that their protective palisade might someday need to be enlarged.

People who drifted in were welcomed. They settled inside the walls, building their huts wherever there was space. Until crowding became an issue, and people had to be turned away. There simply was no room inside the palisade for them, but just being close to the wall provided a kind of security. A few built shacks next to the wall, then more came and built their own shacks. Home was soon surrounded by squatters.

The town's residents helped the newcomers as much as possible. No one wanted to see fellow humans starve or fall victim to predators, but the squatters were quick to take advantage. Why risk hunting or gathering, when the villagers had food to spare?

The dependency could be tolerated to a point, then sanitation became an issue. Cats, wolves, even giant bears might be hiding in the dark! Easier and safer just to do what was necessary where you were. Most did, and the area soon stank like an open privy, which it had become. Finally, when the residents could take it no longer, the squatters were told to leave.

Ruth and Moira, realizing what had to be done, assumed leadership of the undisciplined mob and Francisco became their consort and enforcer. The solution was to build a village of their own. If Home could do it, so could they!

They found a site atop the bluff and a few miles south of Home. There was a spring-fed stream for water and the ground was suitable for building a palisade for defense. The former squatters built New Town, which was soon shortened to Newton. There was no reason to mess with what was working, so Francisco and his consorts remained in charge.

Newton's people soon got the chance to redeem themselves. The river flooded and Home, which had been built in the floodplain, was wiped out. Newton's people helped the refugees build the replacement village farther to the south, perhaps inevitably named New Home.

Bear's Town, located farther to the west, had been named for the founder. The core population had come from Newton and New Home.

Their new village was considerably improved over the earlier designs. The palisade was larger and surrounded by a ditch. It had also been designed with possible future expansion in mind; a new palisade could be joined to the first and a section of wall removed. The interior was also better planned than the others. Passageways made walking easy and ensured that every hut had convenient access.

Winters, even this far south, were harsh, the winds strong, but the pit houses they built for themselves were snug and a simple hearth fire in the center was enough to keep them warm. Local materials were used and construction was easy. The network of relationships that had sprung up between the villagers helped everyone. Who could say when the next disaster would come, or which village might be affected? The only certainty was that whatever happened, the people would help each other.

The leaders, like the townspeople themselves, often met informally to discuss issues that affected everyone. Today's meeting had come about in that way.

***

"Matt intends that I take over the job he was doing, picking up orphaned and injured kids and shuttling them to Prime," Colin said. "It will take up some of my time, but it needs doing and it won't fundamentally change anything, so I'll do it. I'll go where I need to, pick up the kids, drop them off on Prime, and head back here. It will not only save lives, my doing this links every community on Darwin together. The others aren't close enough to meet up like we do, but they know they're not alone. And now that every leader's got one of Matt's signalers, they can get help in an emergency. If a town gets wiped out, we'll send people to help them rebuild. Or if it happens to us, we ask them for help."

Colin drank deep, then topped off his mug before continuing. "New Home pretty much runs itself now, so I can spare the time. But Matt's not done with us, and that may create problems down the trail. Francisco, he wants you to be a diplomat. Assuming we ever manage to make contact with the extraterrestrials, that is, and he wants Lee to be some sort of general. He gave him a jumper too, same as the one he gave me, not that it means anything yet. The jumper hasn't moved since Matt delivered it!"

Colin grinned, and the others smiled back. Matt was influential, no question about it, but there was also no question that Darwin's people were independent. "So far, Lee's refusing to touch the thing. Says he's not going to, short of an off-world attack. He got a hundred rifles too, same as we did, but they're locked up in a shelter he built. He figures we don't need anything we can't make for ourselves."

Colin looked at the others, who nodded back. They understood Lee's point of view. "I don't know when it will happen, but it looks like Matt intends to take our best people. He doesn't have an army or a navy yet, and I'm not sure he ever will, but if he needs one we're it.

"Make warriors out of Prime's people? Good luck with that! Sild did all right after he got here, but as for the rest? Matt's figuring the leaders will come from Darwin, but I doubt it will work. His troops will have to come from that other version of Prime, the one with all those people, and I expect they'll insist on having their own officers in command." Finished with what he wanted to say, Colin drained his mug and went to refill the pitcher.

"I agree about not using what we can't make for ourselves," Francisco said. "We've got the closest thing to an Eden right here on Darwin that a reasonable mind can expect. Everything we need is here, as long as we're willing to work for it, but that's only if we don't try to change things. Old Earth did, and next thing you know the animals were mostly gone and there were too many people! But it won't happen to us. We'll do better, because we have the knowledge the ancients didn't. It won't be easy, though; we're already getting push-back from a bunch of would-be eco-engineers. I, for one, won't let it happen! I'm part of nature, we all are. Instead of changing it, we know it works fine just the way it is, and I'm willing to live with it.

"Far as I'm concerned, those who don't feel that way can emigrate to Prime, but not me. I like Darwin the way it is. One of these days it will get me, but so what?

"A fellow is supposed to have asked once, 'Do you want to live forever?' I don't know that I do. So far, I've got plenty to interest me. Life is good. We're not likely to get sick or be crippled by age even, so I don't see how it could be better. I've got everything here that any man needs or has a right to expect."

"I agree," said Colin as he topped of mugs. "I'll use the jumper to do what Matt was doing, rescuing hurt or orphaned kids and transporting them to Prime, but other than that, it stays parked."

"Unless we're invaded," reminded Bear. "I agree with Lee. I say we depend on nothing we can't make for ourselves and leave things the way we found them as much as possible. Small changes only, so that natural processes aren't overwhelmed. That's really the only way we can keep this Eden you mentioned the way it is."

***

Mesk and Visz were waiting when Matt arrived. He was annoyed at being called away from what he'd been working on, and it showed. "You asked to meet," he grumped. "What have you got?"

"A message, and the sender says he's got something we need to hear. I understand part of it, but not all, and it sounds important so I called you." Mesk handed him a cup of coffee, the new Hawaiian blend, then sat down. Matt glanced at him, eyebrows raised, but Mesk only shrugged and nodded to Visz. Matt found a seat and sipped at his coffee.

"I understand why you named Poim's world as you did," Visz began. "You thought it was like Prime, but it's not. Start with language, they speak a derived form of Portuguese. That means they have a different ancestry and a different culture. Somehow, Portugal or a Portuguese-speaking colony--Brazil, perhaps--became the dominant nation on their version of Old Earth.

"But before that could happen, the previously dominant nations had to lose their position. I'm guessing they probably wiped themselves out, which caused the timeline split that led to Poim's world. Not sure when it happened; so far, I've explored far enough back in their history to know it had to be at least a century ago, and probably quite a bit earlier than that.

"Anyway, we kept on developing, but they started over after the war. And that led to differences, not only in technology but how they live. That war had another result, overpopulation; that's been the post-war norm throughout human history. Which led to a shortage of living space, and what they had was more polluted even than on our version of Old Earth. They needed a solution in a hurry, so they put most of the planet's resources into looking for an answer. They found one, their version of the dimension hopper. It may have been by accident; I haven't gone that far back in their past, so I don't know for sure, but what I do know is that theirs is different. According to their history, that happened just over a century and a half ago. The how it happened is public information, the mechanics of what was discovered are still classified. I haven't managed to bypass that block and I don't want to take a chance on offending them.

"Their controls are built in. They appear to be based on a combination of binary arithmetic and ordinary higher-level functions, but that only tells me how they select destinations, not how the system works. But back to how the dimension hopper changed their society; they had three problems, overpopulation, pollution, and desperation. They considered moving excess people to other versions of Earth, but almost no one wanted to go. Meaning they'd have had to expel them by force, and anyway, it wouldn't have worked. By the time they'd moved a jumper load to a different world, there would have been more than enough births to make up for the ones they'd just shipped out.

"So they kept the people on P 2 and off-worlded almost everything else. As soon as the new farms started producing, they imported the food by jumper. Then they shut down the ones on Poim's world. That freed up a lot of space right there. And while this was going on, they were also geo-engineering Poim's world. The deserts aren't. The Sahara, the Gobi, the Kalahari, the North American west and all the other former dry areas are gone, vanished. They're drier than the tropics, but not by all that much. A lot of people live there now.

"They built new villages wherever they could find room, piped in desalinated ocean water, and over time forced local ecosystems to change. They could do it, because they needed the space and they didn't have to worry about all the national borders that Prime had back in the 21st Century. The war, or maybe a series of wars, saw to that.

"Poim's Earth is a mass urban area now, nothing but wall-to-wall people. Food production is on a different Earth, probably several Earths. They're all versions of Earth, but on different dimensions. Mining, manufacturing, waste disposal, everything not involved in day-to-day living is on another dimension. They manage, but only because they can easily cross dimensions. And so far as we know, Prime, Poim's World, and a few others that are almost identical to ours have that kind of dimension-crossing technology.

"The Poimies knew something of space travel, but they never progressed beyond rockets. They never discovered the electronic impeller drive, but it didn't matter; access to an alternate Earth beat anything they could have found in the solar system. They never quite abandoned the idea of space travel, but they never devoted a lot of resources to it either. It never went beyond the early stages, because dimension crossing was better. The people interested in space now are motivated more by nostalgia than curiosity.

"Now look at what they don't have," Visz continued. "No Central, and no matter converter. Those are critical to understanding why their society is so different from ours. Dimension hopping made it all possible; they didn't need a Central, because they had people to do what Central does for us. No matter converter, because they had more resources than we do, still do, because there are an infinite number of Earths to exploit. And they're constantly exploring to make sure they don't run out of resources.

"The upshot of all this is that they are present in a lot more dimensions than we are. We've explored other dimensions, it's how we found Darwin, but we never did more than visit. We went in just long enough to find out whether the planet had a human presence. And when we found one, we never tried to contact them.

"We had no need to, and considering our shrinking population, plenty of reasons not to. Which is probably why the raiders encountered them but never found us. So far.

"On Prime, we had highly developed space travel and gave it up. We didn't need it, because we had Central and the matter converter.

"Plus overpopulation wasn't our problem, quite the opposite. It's an unfortunate side effect of pervasive electronic communication; our population had begun to shrink."

Mesk interrupted briefly. "You've done a lot of work! Just curiosity, or something more?"

"A lot more," Visz said. "You'll understand, but I need to get there in my own way."

Mesk nodded and sat back, waiting.

"Now we need to look more closely at our history," Visz continued, "particularly developments that led to other discoveries. About a century after the international computer network started operation, a team of mathematicians and scientists at MIT worked out the basics of controlling and focusing energy fields. The MIT people took the lead, but half a dozen other US universities contributed. China, Russia, Europe too, and not just people, because the research wasn't cheap. We'd had worldwide wars, but this was the first worldwide science project.

"Anyway, they learned how to manage energy fields, but figuring out how to convert nuclei didn't happen overnight. Synchrotrons and the LHC smashed nuclei apart using high velocity particles; the new high-density energy fields smashed particles together using a brute-force approach. In the process, they found they could create new elements.

"Portable matter converters can create light elements using even lighter ones as building blocks, but the big industrial units can even create trans-uranics. Not that we need them, because their half-lives are too short for them to be useful, but the technology is there if we ever need it.

"Translating theory into what became the M-C technology was again a team effort, the second worldwide science-engineering project, this time including engineers from different nations. Grad students and post-doc fellows too; a lot of people worked on the project. They were happy to get the opportunity, because the M-C was cutting edge technology. And they coordinated everything through the network that by then they'd started calling 'the Web', and it was, a web linking everyone and almost everything on Earth.

"The first matter converter was crude. It absorbed an enormous amount of energy and needed an enormous building to contain it, one made with non-magnetic materials. It used the very powerful internal fields that nowadays are shielded by an equally-powerful field, but they lacked the technology back then to do that. And while they were working on improving and shrinking the MC, they discovered the dimension jumper.

"Both are based on the same principles, and for that matter so is the electronic impeller drive. There was an earlier electromechanical version, a sort of hybrid. It was maintenance intensive, but it worked. The electronic version is in all ways better. The important thing is that one discovery led to another, and the Web was the key. Everything, literally everything, was available somewhere on the Web, as were a number of artificial intelligence programs. They began interacting with each other.

"At some point, the AI developed a kind of sentience. That made it much more powerful; it could not only manage the flood of data, it could analyze it and integrate it. That sentient Web is what we now call Central. Without that sense of self-awareness that enabled Central to not only use information, but improve on how it's distributed and used, we might never have discovered the matter converter or the dimension jumper.

"But we had Central, then the MC, and after that the dimension hopper. Poim's world didn't. Best guess, their timeline split from Prime's at least two or three centuries ago, but probably less than four. Again, it's only a suspicion, because I haven't gotten that far back in their history. There are similarities, but also an enormous number of differences, and so far no shared point of convergence.

"They have a computer network. It's not aware, in the sense that Central is, but I suspect that's only a matter of time and added complexity. They have their version of the dimension hopper too, meaning that within a generation or two his people would have discovered the matter converter."

"Not sure I follow," Mesk said. "Ours became sentient, theirs didn't. Why didn't their computer net develop sentience?"

"The war I mentioned almost certainly went nuclear," Visz explained. "It would have had to, in order to wipe out the dominant nations of the time. A nuclear exchange meant repeated EMP's, which almost certainly destroyed their network. Best guess, the replacement net doesn't have nearly the capacity that Central does, nor does it have as many nodes. Maybe it hasn't been around long enough.

"Even so, the replacement network was good enough. They discovered how to build that first jumper and in a sense, that led to a kind of dead end. They put all their resources into perfecting dimension-crossing technology.

"Instead of looking for other planets, they just jumped to other versions of Earth. If by chance they found themselves on an inhabited version, they left right away. There were plenty of others with no people."

"Okay. That makes sense," Matt said. "They're in thousands of dimensions, we're in a bare handful and only two, Prime and Darwin, have more than a handful of people.

"None of this explains who the aliens are," Mesk said thoughtfully, "but it tells us a lot about them. They need resources, which is why they were exploring. Not just new territory, but mineral deposits. That would explain why it was a prospecting team they hit, and it also tells us that they don't have the matter converter. They didn't have a dimension jumper either, until they grabbed Poim's ship. So, probably no knowledge of how to control really strong energy fields.

"The attackers are almost certainly from Poim's dimension. There are likely to be related versions on our dimension too. We don't know that, but we also don't know there aren't any, so we have to prepare.

"Which means we need an effective defense. If they attacked Poim's people, there's no reason to suppose the ex-tees of our dimension won't attack us.

"We also know that they have an advanced form of space travel, probably on the level of what we gave up. But until they captured that jumper, they had not been able to cross dimensions. They were on a world where they can't live without supplementing their air. They were exploring what to them is a marginal world.

"They immediately attacked, because externally the jumper didn't look anything like their ship. It represented a different technology, probably higher than theirs, and that tells us quite a bit more about them. Quick to attack means that they have enemies. Our people, Poim's too, would have simply left that version of Earth to them. They want it, we don't need it, why fight over it? But they didn't give Poim's scouts a choice. They're also non-human; that's why they took the bodies of the scouts, to figure out who and what they'd run into. Conclusion, they're probably our equal in space technology or nearly so, but not in other areas. They want advanced technology and they need mineral resources, but they needed help to breathe on the version of Earth they attacked. That means they're not interested in Earth as living space. That's a lot of guessing, so what do you think? Does it sound correct?"

"There could be a different explanation for the air tanks," Matt said thoughtfully. "What if they're afraid they'll pick up diseases? Or vermin? If you lived on a planet without flies or fleas, wouldn't you do everything you could to avoid importing them?"

"Point," Visz admitted. "But then there are the legs that bend backwards."

"There are Earth species that do that," Matt countered. "Quadrupeds are like that, hind legs that flex in the opposite direction. It's really not that different, just longer or shorter bones between the joints, and their arms appear to be roughly the same as ours."

"But they grabbed the bodies!" Visz argued. "That points to a different species. They expected to run into enemies, but not humans. So they took specimens."

Mesk nodded. "We can't be certain until we have a one of them to examine, but that doesn't mean we shouldn't be thinking about it now. And that's all we've got so far, thinking, because they haven't been back yet. No raids, or none we know of, just--nothing."

The other two were digesting that when Central interrupted with a priority communication alert.

"Accepted. Deliver your message," ordered Mesk.

<Message from space, possibly the ship that Mak and Zelle were in when communications ceased.>

"Central, question: why the ambiguity?" Matt asked.

<The communication protocol is different. The voice is Mak's, probability in excess of 90%, but response is slower than expected. Second voice, Zelle, probability greater than 87%.>

"Could Mak and Zelle be on a different ship? One from the other Prime, perhaps?"

<Unlikely, Matt. Differences are less than 12%. Probability, damage to their ship. Possibility exists that Mak repaired the radio or otherwise found a way to communicate.>

"What did the message say?" Mesk asked.

<'Request assistance.' That message repeated several times, then stopped.>

"We have ships available, do we not?" Matt asked. "How long to arm one? Based on what happened to Poim's scout, I think we need weapons. "

<The need was foreseen. Ships are available. One standard day to convert large industrial lasers to laser cannons suitable for use in space. Four standard hours to install and test them. Estimated time to completion, 28 hours.>

"Arm three ships and deliver them here when they're ready. Plot a course; direction, closest estimate to the vector that signal came from."

<Commands acknowledged.>

Matt stood up, refilled his cup, and left. Bare moments later, he boarded his jumper and told Central his destination. He was going to Darwin; the people there would need to know about this latest development.

He would fly one of the ships, but what about backup? Poim and Joao, perhaps? For a moment, he felt a pang of grief. Once, that someone would have been Lilia, but she had grown tired of waiting. His family, the children...

Well. Matt shrugged off the depression that had taken him by surprise. He tried not to think about what he'd lost, but... She wouldn't have to wait long before she found a new consort.

And in the final analysis, he'd had no choice.

Matt suppressed his feelings and tapped the screen, heading for Bear's Town.

"Central, can you get a message to Poim?"

<Yes, Matt. I will record your message, send a jumper, and radio him when it arrives on his world.>

"Message as follows. We've heard from Mak and Zelle. If you'd like to go along on the rescue, meet me on Prime. Add a time, when the ships I ordered will be completed, and a location where they'll be waiting."

<Command acknowledged, Matt.>

 

Chapter Three

Matt decided that the best place to meet Poim and Joao was at the nearest spaceport, in this case 189km east of the central Rockies. He sent a quick message via Central and boarded his jumper for the short flight.

The three ships he'd ordered were waiting, parked side by side in the center of the hardpan.

Matt barely glanced at them; he'd received a quick memory download right after returning from Darwin. As a result, he now 'remembered' having flown similar ships dozens of times. Identical, except for the armaments that Central had added on; unlike Mak's scout, the new destroyers, Matt's name for them, packed a punch.

"As my message mentioned, we've heard from Mak and Zelle. I'm going out to rescue them and I thought you might want to come along. I also intend to have a look at what crippled their ship."

"Certainly," said Poim. He glanced at the field and frowned at the nearest ship. The menacing black hull dwarfed their jumper.

"Three ships; does that mean we'll each be piloting one? We've never flown anything that big; our ships are larger at takeoff, much smaller after the booster rockets fall away. Our biggest is less than half the size of these."

"Not a problem; the computer will fly it. You've at least been to space, according to Central's records, which is one reason I asked for you. I also want to familiarize your people with our ships. The ship that hit your jumper came from space. Which means you'll need ships of your own."

"We've flown," Joao acknowledged, "but only as far as the moon. Even so, I understand why you would want us along; dimension crossing isn't the same thing at all. One moment you're at home, the next you're on a different Earth. We've never been able to measure the interval.

"But space is different; the trips take a lot longer, plus you're surrounded by vacuum. If your ship leaks, and it's happened a few times, the suit will save your life. Had we known what you had in mind, we'd have brought our pressure suits. They're tailored to us."

Matt nodded. "I understand your caution, but our ships are different. Your rockets go as far as the moon, while ours were designed to spend most of their time out in the Big Dark.

"Start with the hulls; ours are ceramic, and each sub-section is cast as a single unit. The sections are welded together during assembly, so the hull becomes equivalent to a single ceramic casting. No leaks, in other words, and no weak spots, other than the entry port, and because of the thickness and the beveled design it's really not weak at all. That space just behind the entry is an airlock. The inner door is closed during flight, which adds an additional margin of safety.

"The hulls can be disassembled for upgrading, but again, during reassembly they're re-welded into a single unit.

"Central assured me that the ships are perfectly spaceworthy, and maybe they are, but if necessary one ship can accommodate all of us. Long enough to get back to Earth, at least. And even if the ships are as perfect as Central claims, something happened to the one Mak and Zelle took.

"Accident? Enemy action? Since I don't know, it's better to be safe than sorry. It's one of the reasons why I wanted three armed ships.

"There are half a dozen life-support suits on board each. They may not be an exact fit, they're there in case we have to go outside the hull. I doubt you'll need them, but I might.

"We don't know what happened to Mak and Zelle. If their ship is damaged to the point my ship can't make an airtight seal with theirs, I'll figure out how to extract them.

"As to the suits, you'll learn more about them after we're on board. The information's in the computer. By the way, you'll interface with the computer using helmets, but other than that your ships are identical to the one I'll be flying."

Matt noticed the glances they shared with each other as they approached the ship; his comment about the computer doing the actual flying hadn't reassured them.

But perhaps a complete briefing, using the information he 'remembered', would.

"Length of this model, a destroyer, is 147.5 meters. The mean diameter of the hull is 61 meters." He passed by the open hatch and headed for the ship's nose, a blunted cone whose flowing lines were interrupted by four equally-spaced projections. Rounded in front like the nose itself, they blended seamlessly into the hull about four meters ahead of where the curve flattened to become the ship's midsection.

"This is the bow. The term doesn't mean much, the impellers can fly it in any direction including sideways; but since this is where the lasers are mounted, 'bow' works as well as any."

"Each ship has four laser cannons with a 50cm discharge lens. Power output can be varied to an extent, so we rate them by the diameter of the optical cavity. The lenses are in the domes, which are normally closed as you see them now. The domes retract as soon as the accumulators begin powering up.

"They can be aimed, but only enough to vary the common focus point. That's less than a fourth of a degree in any direction, so for practical purposes they're fixed. You designate the target, the flight computer aims the lasers by pointing the ship at the target. Right now, they're set to converge at their minimum range, 1000 km. That's for safety; any closer, you're likely to hit debris from the explosion.

"They can be fired one at a time or salvoed, meaning all four are fired at the same time. That gives you the equivalent energy output of a two-meter laser, something even Central hasn't been able to cram in a ship this size.

"I asked, and the answer I got was that in order to carry a reactor capable of powering four one-meter lasers and the bigger systems such a ship would need, it would have to be at least ten times larger than this one. It's not just the lasers, it's the cooling systems and everything else that goes with them. A bigger ship would also need more powerful propulsion units and a larger power plan, probably more than one. Doable, according to Central, but such a ship--they'll be called cruisers, if we ever build them--wouldn't be nearly as flexible as this model. But if it turns out later on that we need them, Central assures me it can be done.

"The lasers pack plenty of offense, but even so, weapons management is important. If you salvo all four, you're looking at 30 seconds to a minute before the systems return to nominal. Until they do, the lasers are out of action.

"But Central assures me that no known armor can survive that jolt, so other than in training, I doubt you'll ever need to fire all four at once. The lasers don't just burn their way through a hull; that many joules, delivered to a single point in less than a millisecond, is equivalent to exploding a fair-sized nuke. Approximately a meter of hull, depending on the focus setting, is converted to a superheated plasma. The hull material itself forms the fireball."

Matt glanced at the other two to make sure they were following the discussion. They were.

"If you alternate the discharges by firing one laser at a time," he went on, "you'll be able to fire continuously until the waste heat builds to a dangerous level. If you fire them as pairs, you'll be unable to fire for at least ten seconds after both pairs are discharged. Recycle time depends on power plant output, the capacity of the cables to carry the necessary current, and again, how fast the waste heat can be dumped off into space.

"Opening the louvers over the radiator fins...they're located in the after part of the hull...increases efficiency, but a couple of minutes of discharge will leave you glowing like a comet until the heat bleeds off. Meaning that if your enemy is using an infrared tracker or missile, passive countermeasures won't work; you'll have to try to target an incoming missile with your lasers, meaning even more heat buildup. It's a vicious cycle that can bite you in the ass, so think about what you're doing. You can think ahead, the flight computer may not be able to. Its response will always be predictable.

"Fortunately, the lasers are not your only armament. You've got four railguns, one on the end of each stub wing, that can be aimed ahead or behind. If you fire them at a 90º angle, the recoil will cause flight problems. Fire all four while they're pointed up or down and the ship will end up spinning like a top. While spraying copper slugs in a circle. I suggest you avoid doing that unless you're surrounded and enemy ships are attempting to board. But first, make sure there are no friendlies in the vicinity; the slugs don't care who they hit.

"The magazine bays are in the wings, the only place we had room for them, but since the guns are mounted on the wingtips it works out. Mags hold 50 slugs and are modular, so reloading is simple and fast. Release the four locks, pull out the three empties, plug in full ones and lock them in place. The mags mate up with slides after installation. When one is expended, it's dumped and the next slides into position. Feeding slugs to the railgun takes place automatically.

"Two issues to keep in mind; counting the ready magazine and the three in reserve, you've got 200 slugs per gun. Magazines can only be loaded into the gun bay when it's pointed ahead, the normal position unless you ever find yourself being pursued or, as I mentioned before, surrounded.