“So a ship traveling at infinite velocity could fly right through a star without any trouble.”
“That’s the theory, sir. The point is that once you’ve accepted the existence of hyperspace gates, you’ve introduced a fundamental change to the laws of physics, one that we don’t yet fully understand. Maybe the gates fold space. Maybe they fold time. Maybe they do both, or something else entirely. We simply don’t know. So time travel would not be the strangest imaginable consequence of hyperspace gates.”
Huiskamp nodded. “Do you see that helmet behind you?”
“Yes, sir.”
“Take a good look at it. What do you think?”
“Looks like a standard IDL helmet, but without the lining or identifying features. Badly weathered, like it was left out in the sun for a long time.”
“Do you think that much weathering could occur in three years?”
“I suppose so, sir. Depending on the environment.”
“What if I told you that helmet is thirteen hundred years old?”
Haas regarded the admiral cautiously, as if expecting a trap. “Are you… saying this helmet is… an artifact of some ancient alien civilization?”
“No. I’m saying it’s an IDL helmet that was manufactured three years ago and yet has somehow experienced thirteen hundred years of weathering.”
“Oh,” said Haas, his eyes affixed on the helmet. Huiskamp could tell he was wondering just how bad the admiral’s head injury was.
“Lost your fondness for the idea of time travel?” Huiskamp asked.
“Well, sir,” said Haas, rubbing his scalp. “It’s just… if you ask me whether God exists, I will probably tell you that it’s not a possibility I can discount. But if you tell me God is waiting for me in the corridor….”
“The way things are going, Haas, we’re all going to meet God a bit sooner than we had planned. In the meantime, though, we’ve got some harsh realities to deal with. One of them is that space helmet. I have some reason to believe that it is thirteen hundred years old despite having been manufactured only three years ago. I’m asking you if that’s possible.”
“Theoretically, sir. Can I ask what the evidence is?”
“I’ll show it to you if you like, although I don’t think you’ll find it very convincing. What I want to know is whether it’s possible that someone wearing that helmet went through a hyperspace gate three weeks ago and reappeared in the year 883 A.D.”
Haas thought for a moment. “Sir, are you talking about Andrea Luhman?”
“That’s right.”
“Huh.”
“Care to elaborate, Haas?”
“Sorry, sir. It’s just… this has been bothering me since we received that final transmission from Andrea Luhman. We’ve seen gate failures before, but nothing like that. Even when the Cho-ta’an hit that frigate and it drifted halfway through the gate before the connection was severed… the total mass was conserved. The frigate was cut in half like someone had taken a laser to it, but it was all there—one section in the Gliese system and one in Alpha Centauri. Gates don’t make things disappear. They’re always in one place or the other. So it never made any sense that Andrea Luhman just vanished.”
“She could have gone through another gate. Maybe one of the Cho-ta’an gates.”
Haas shook his head. “We’ve never had a failure with a gate like that. You tell the gate where you want to go and it takes you there. The code we send to a gate isn’t like a key that unlocks a padlock. It’s more like a set of notes we play on a piano to create a particular chord. If the gate receives the notes for the Sol gate, it will take you to the Sol gate. If the notes are wrong or the gate malfunctions, it isn’t going to work at all. It won’t just send you to some random gate.”
“But would it send you back in time?”
“That’s your theory, not mine, sir. But I will say that it doesn’t make any less sense than Andrea Luhman showing up at an unknown gate—or disappearing entirely.”
“Why do you say that?”
“The time variable is the one we understand the least. If you send the right coordinates to a gate, it will take you to your destination. That’s an axiom that’s been tested thousands of times with a perfect success rate. But what if there’s an additional data point that we’ve been supplying to the gates without realizing it?”
“What data point is that?”
“Relative velocity, sir. Andrea Luhman went through the Fomalhaut gate faster than any ship has ever gone through a gate before. We don’t have any data on what happens when a ship goes through at nearly a third of light speed.” He glanced at the helmet. “At least we didn’t.”
“You’re suggesting that the code we transmit is the spatial coordinates and the velocity relative to the gate is the time coordinate?”
“It’s one explanation, sir.”
“If that were the case, every ship going through a gate would travel backwards in time. The fastest any ship has gone through a gate before Andrea Luhman was what, a tenth of light speed? Why didn’t they go back in time?”
“Maybe they did, sir. The function might be logarithmic.”
“Meaning that it would be much more pronounced at higher velocities.”
“That’s right, sir. Maybe traveling point zero one light speed takes you back a second. Point one light speed takes you back an hour. Point three light speed takes you back thirteen hundred years.”
“Half of light speed takes you to the dawn of humanity. Full light speed takes you to the birth of the universe.”
“Something like that, sir. Although there are some theoretical—as well as practical—problems with accelerating a ship to more than about ninety-nine percent light speed.”
“Even so, wouldn’t we have noticed this effect, even at lower velocities?”
“Not necessarily, sir. Understand that there is no such thing as universal time, which means the idea of traveling across space instantaneously is really no more than a helpful approximation. If you’ll allow me to indulge in an illustration, sir?”
“Go ahead.”
“A ship disappears from the Gliese system at time t1. It appears in the Geneva system at time t2. According to the ship’s clock, no time has passed. But are t1 and t2 simultaneous, or are they a second apart? Or an hour? Or a week? How would you know?”
“We do have Galactic Standard Time.”
“GST is determined by pinging the gates. The gates talk to each other through hyperspace and agree as to the current ‘standard time.’ But the system assumes that gates are communicating in real time, which begs the question: what is real time? So the problem is circular: how do we know hyperspace travel is instantaneous? Because the gates tell us it is. But what is instantaneity? It’s whatever the gates tell us it is.”
“You mean the gates could be lying to us.”
“No, sir. I mean there’s no objective reality for the gates to lie to us about.”
“But if there is no such thing as universal time, and the gates are presenting us with a version of universal time, then isn’t that a kind of lying as well?”
“I suppose so, sir. Keep in mind that the transmitters and receivers on the gates are human embellishments. All the gates themselves do is relay the message. So it’s really our fault for using the gates for something that perhaps they weren’t intended for.”
“You think we’d be better off without GST?”
“I think GST is a benign fiction, like simultaneity itself. The fact is, human brains weren’t designed to deal with the effects of travel at velocities even a small fraction of light speed. We’re wired to think of time as a constant, like the sun rising and setting. But it’s not. If you’ll allow me another illustration: suppose you have two atomic clocks perfectly synchronized to each other. The clocks are located in between the Gliese gate and the Geneva gate. Using conventional space travel, you transport clock A to the Gliese gate and clock B to the Geneva gate. But as it happens, the origin point for the clocks is p
hysically closer to the Gliese gate than to the Geneva gate, so in order to get the clocks to their destinations at the same time, you put clock B on a faster ship.”
“I get it, Mr. Haas. Velocity causes time to slow. Now the clocks are out of sync, and we don’t know which is the ‘real’ time. But why not just make sure the origin point is directly between the two gates and that the two ships travel at exactly the same velocity? Then the clocks would remain in sync, yes?”
“You could do that, yes. But the fact that you have to go to such lengths to make sure the clocks stay in sync suggests that simultaneity isn’t a property of empirical reality, but rather an artifact of the way you conduct your experiment. If I have a thermometer that is only accurate as long as the temperature is precisely forty-six degrees Celsius, then I don’t have a useful thermometer. If I can determine simultaneity only in one very particular and rare set of circumstances, I don’t have a useful way of measuring simultaneity.”
“I see.”
“And it gets worse, sir,” Haas said. “This is all theoretical. That is, because of the principle of general relativity, I know that velocity causes time to slow, and therefore that the clocks will be out of sync by a certain amount. But at interstellar distances, I have no practical way of checking the accuracy of the theory. Suppose I travel to the Gliese gate and you travel to the Geneva gate. I record the time on clock A and send it in a message to you at light speed. Gliese and Geneva are about eight point two light years apart, so it takes eight point two years for the message to reach you. Assuming that exactly eight point two years has passed for each of us, you know that the time on your clock should be precisely eight point two years later than the timestamp in the message. So far, so good. But this illustration assumes that the Gliese gate and the Sol gate are stationary relative to each other, and that’s not the case. Like any two points in the galaxy, they are moving away from each other. That creates a problem for us, because light speed is a constant, meaning that it is the same relative to the Gliese gate and relative to the Sol gate, even though the two gates are moving at different velocities relative to each other. The message I send you is traveling away from me at exactly light speed, but it is also traveling toward you at exactly light speed, even though we are moving away from each other.”
“You’re losing me, Mr. Haas.”
“Maybe a more conventional illustration will help. Suppose I’m on a train moving slowly away from a train station. We want to verify that the clock on the train shows the same time as the clock at the station, but I can’t stop the train, and we have no radio. So while you stand outside the station, I write down the time on a baseball and throw it a few seconds after the train passes.”
“You call this conventional?”
“In a manner of speaking, sir. Suppose, for the sake of illustration, that zero time elapses between the moment I write the time on the ball and the moment I throw it. You catch the baseball and mark the time at the station at that moment. You see the time I’ve written doesn’t precisely match the time on the clock at the station. Why is this?”
“Because it took some time for the ball to reach me.”
“Right, sir. To calculate how much, you just need to know how fast the train was moving and how fast I threw the ball. To simplify things, we’ll assume you also know exactly how far I was away from the station when I threw the ball. My velocity relative to you is simply the velocity of the baseball minus the velocity of the train. Suppose the train is traveling away from you at ten kilometers per hour and I throw the ball toward you at fifty kilometers per hour. The velocity of the ball relative to you is therefore forty kilometers per hour. Suppose that I’m precisely forty meters from you when I throw the ball. Traveling at forty kilometers per hour, the ball takes a thousandth of an hour to reach you. There are thirty-six hundred seconds in an hour, so that’s three point six seconds. You find that this is the exact difference between the time written on the ball and the time you caught it. Problem solved. The clocks are in sync. Well, close enough for a train schedule, anyway. Thanks to general relativity, there will still be a tiny discrepancy, but nothing to worry about on a practical level.
“Now let’s get back to our hyperspace gate problem. Instead of a train, I’m at the Gliese gate. Instead of a train station, you’re at the Geneva gate. I’m moving away from you at a velocity of around sixty-eight kilometers per second. Instead of throwing a baseball, I send you a timestamp via laser. You compare the laser timestamp to the time on the atomic clock at the Geneva gate and find a discrepancy, but because of your experience at the train station, you are now confident that the discrepancy is a result of the delay between me transmitting the message and you receiving it. So you perform a simple calculation to determine the velocity of the message, subtracting the velocity of the Gliese gate (relative to you) from the speed of light. Light travels at 299,792 kilometers per second, and the Gliese gate is moving away from you at sixty-eight kilometers per second. The message therefore traveled at…” Haas tapped at his wrist comm. “…299,724 kilometers per second, or slightly less than light speed. Do you see the problem, sir?”
Huiskamp thought for a moment. “The message was sent by laser. A laser beam is light. The speed of light is a constant.”
“Exactly. A beam of light can’t travel at less than light speed. Relative to any given point, it always travels at 299,792 kilometers per second. That means the message’s velocity relative to you is light speed, and the message’s velocity relative to me is also light speed, even though we are moving away from each other. This is the tiny discrepancy I mentioned earlier. Except at these velocities it’s no longer tiny. It’s as if the baseball’s velocity were the same whether or not you accounted for the movement of the train.”
“How is that possible?”
“Well, velocity is a measure of distance traveled over time. If the velocity of the message is the same for both of us, and the distance between the Gliese gate and the Geneva gate and their velocities relative to each other are known variables, then something else has to give.”
“Time.”
“That’s right, sir. So in trying to determine whether our two clocks are in sync, we have actually made the problem worse, because we’ve had to bend time to compare our two measurements. And of course we could take a shortcut by transporting both clocks to one of the gates and then sending one of them through to the other gate, but then we’re once again assuming the fidelity of what we’re trying to check. If I send a clock from the Gliese gate to the Geneva gate at one kilometer per hour, it will remain in sync when it gets to the other side. If I send a clock through at half light speed, it will remain in sync when it gets to the other side. In both cases, no time has passed according to the gates. Perfect simultaneity. But is this simultaneity a property of spacetime or is it an artifact of the gates? It all becomes hopelessly muddled after a while. So we take shortcuts, the same way we do with space. We assume the gates are telling us the truth when they tell us what time it is, but what they actually provide is a helpful approximation.”
“But an approximation of what? If time is just an illusion, then what are the gates giving us?”
Chapter Eighteen
Despite the hopeful picture Jason had painted for Lauren Foley, Freedom had no good options. With her current acceleration, she couldn’t outrun the Cho-ta’an ships. If by some miracle she were able to eliminate the eleven ships on her tail, more would be coming. Those that had destroyed Philadelphia and Renaissance had probably already started decelerating and heading back her way. Freedom was seventy-two days from the Chrylis gate at its current speed and acceleration, and even if she could reach it—and the Cho-ta’an hadn’t already seized it—the ships on her tail would just follow her through. Unless she could rendezvous with another ship beyond the gate, she’d be stuck facing another wave of Cho-ta’an ships alone. Her best bet had been to rendezvous with Kilimanjaro in the Procyon system, but they still had received no word from Admiral Chiang. In a
ll likelihood, Kilimanjaro had met the same fate as Philadelphia and Renaissance.
Even if Kilimanjaro were still online and Freedom could get to the gate ahead of the Cho-ta’an, there was another problem: piloting a large ship like Freedom through a hyperspace gate at much more than ten percent of light speed was extremely dangerous. The gates were three hundred meters in diameter, providing a sizeable margin of error for a small ship traveling at a few thousand kilometers per second. But Freedom was nearly fifty meters at its widest point, and if it maintained its current acceleration, it would be traveling at nearly a quarter of light speed by the time it reached the gate. The slightest miscalculation or variation in thrust at that velocity could be catastrophic.
By the same token, a slight course correction at this point would cause them to miss the gate completely. That was probably the best option, as bad as it was. If the Cho-ta’an had wasted some of their missiles against GODCOM, there was a chance Freedom could fight them off. Worst case, she would at least draw them away from the Geneva system for a few weeks. There were still a few smaller IDL ships left in the Geneva system. If they could figure out how to trigger the failsafe on the Geneva gate—or wreck it the old-fashioned way, with a kamikaze run—they would hamper the Cho-ta’an’s ability to move more ships into the system. Without a lot more ships, it would take the Cho-ta’an a long time to subdue Geneva itself. Most of the population would starve, but some would survive. As long as humans held the planet, they could conceivably build more ships and retake the system.
No, Jason thought. It was no good. If the Cho-ta’an hadn’t seized the Chrylis gate as well, they would soon, which meant that destroying the Geneva gate would be of minimal help. As long as the Chrylis gate was online, the rest of the Cho-ta’an fleet was at most a year away from the Geneva system. Even if the idiots running Geneva could get their act together in the face of the Cho-ta’an threat, that wasn’t nearly enough time to build a fleet of warships. The only way the Genevans would have a chance to fight back was if the Chrylis gate was out of commission as well.
The Legacy of the Iron Dragon: An Alternate History Viking Epic Page 12
