“High up enough that it won’t flood before 2040.”
“But that still leaves a lot of choice.” She thought about where Cape Canaveral had been situated-on the Atlantic shore, the eastern coastline of America. Why there? For safety reasons, she remembered. You always launched rockets eastward, to get a boost from Earth’s own rotation. Launching from Canaveral had meant that any failure would result in a rocket, flying east, falling harmlessly into the sea. Now the same principle surely applied. “Look,” she said, stabbing a finger at the map. “Gunnison. Twenty-three hundred meters above the old sea level. In 2040 it will be close to the eastern coast of the surviving land. A safe place to launch east.” What else? She dug her handheld out of her bag and quickly interrogated it. “The town’s on a valley bottom, so plenty of flatland. There’s an airport nearby, so you have transport links, and this reservoir, the Blue Mesa, can provide water. And it’s a college town, so there’s a population of workers already in place-”
Harry Smith approached them. “Actually that took you only four minutes. Yes, that’s why Gunnison, Colorado, is going to host the world’s latest, and maybe last, space launch facility. Twenty years ago you’d never have believed it. Good bit of deduction, Ms. Groundwater. OK, you’re free to go.”
They got to their feet, handed back the atlas, and ran for the stairs.
“And, Ms. Groundwater- don’t be late again. Next time you might find somebody else sitting in your seat…”
12
When they got to the classroom, in the back of a large, emptied-out chamber labeled “Edge of the Wild” on the museum’s second floor, Liu Zheng was in full flow. He stood before an interactive whiteboard, rapidly assembling and erasing graphics, and allowing annotated equations to scroll by. “The essence of an Alcubierre warp bubble is simple,” he said. “Conceptually at any rate. You have an isolated region of spacetime.” This was marked as a circle on his two-dimensional diagrams, but he mimed a sphere with closed hands. “Your spaceship is in this zone here…”
As he talked, a dozen kids all about Holle’s age sat at tables before him, and worked at handhelds and laptops, muttering and murmuring in pairs and threes. Zane led Holle to an empty table. As she passed, the students glanced at her indifferently and looked away.
Holle recognized a few of the kids in here, including Kelly Kenzie, a friend or maybe rival since they were little. Kelly was locked in intense conversation with a red-haired boy who looked a bit older. There were Cora Robles and Susan Frasier working in a huddle, two bright, pretty girls together. And Thomas Windrup and Elle Strekalov, sitting so close they might have been conjoined twins, as they had been all the way through grade school. Elle was a lot better-looking than Thomas, and the class gossips didn’t know why they stayed together. There was a lot of noise in here, and among the noisiest were Joe Antoniadi and Mike Wetherbee. Joe, an Italian-American whose family had fled New York, was likable, friendly, easy to impress. Even as Zheng talked, Mike was cracking jokes in his broad Australian accent and making Joe laugh. Mike’s family were refugees from an almost entirely abandoned continent.
They reached their table. Zane had a laptop, and Holle dug her handheld out of her bag.
If the students had been indifferent to Holle, Liu Zheng didn’t so much as register her presence. He just carried on with what he was saying. “So how do you fly to the stars? Well, you engineer the space-time metric. You arrange it for spacetime to expand behind you, mimicking the inflationary conditions of the early universe. And you make spacetime collapse ahead of you, mimicking a black hole, say. Thus your spacetime bubble is pulled and pushed, driven ahead across the manifold. You are riding a propagating wave in spacetime.”
“Like surfing!”
“Yes, Mr. Meisel. Though I myself have never surfed.”
Holle thought she understood. The spacecraft would be embedded in spacetime like a toy insect in a block of glass. You didn’t transport the ship itself, but a whole chunk of the spacetime around it.
“This is the essence of the warp bubble. The transported spacetime must be large enough to keep you away from the regions of heavy curvature associated with the warp bubble itself-which would manifest, of course, like strong gravity fields. But what of travel faster than light? Einstein tells us that it is impossible to move faster than light-speed as measured against local landmarks. ” He emphasized the words heavily. “The trick is to carry those landmarks with you. The ship itself is not traveling at all relative to the spacetime bubble around it. It is the bubble itself that propagates at multiples of light speed, as desired. You are not traveling faster than light, because you are carrying the light with you…”
Zane was already working, paging through notes on his laptop. Holle arranged for the board’s contents to be downloaded to her handheld, and she made notes alongside Liu’s diagrams and equations. All around her the students chatted, argued, joked, and scrolled through what looked like entirely disparate bits of work. This was not like the mostly calm, mostly studious atmosphere she had got used to at the grade schools in Denver.
“The warp bubble as a method of transportation has some paradoxical properties. Because the ship is stationary relative to local landmarks, there are none of the effects we associate with special relativity: no time dilation, no Lorentz-Fitzgerald contraction. Clocks aboard the ship stay synchronized with those at the starting point, and indeed at the destination. And there will be no inertial effects.”
“What does that mean?” Holle whispered.
“You wouldn’t feel any acceleration,” Zane said. “The ship’s not moving compared to the spacetime it’s embedded in. So you don’t get squished against the back wall of your cockpit when you turn on the warp drive.”
“However, there are issues of control, for you run the risk of outrunning any signal sent forward to control your own bubble. Therefore, we think it likely that any piloted mission will have the parameters of bubble formation, propagation, dissipation and so on loaded by a remote station before launch; the crew of the starship inside the bubble will essentially be passengers.”
Joe and Mike burst into gales of laughter over some private joke.
Holle leaned over to Zane. “Is it always like this?”
“Like what?”
“Noisy. Everybody messing around.”
He shrugged. “There are no rules. They just put the material in front of you and expect you to make what you can of it.”
“And if you can’t cope with that,” said the boy next to Kelly, twisting back, “you can go back to the kiddie schools and play with the plastic bricks. There’s always somebody ready to take your place.” He grinned. “Don Meisel. Who the hell are you?”
Holle found herself blushing as she told him her name. A year older than Holle, Kelly was growing into a tall, confident blonde, no great beauty but a leader. And this boy Don, who Holle hadn’t met before, looked that bit older again. His eyes blue, his hair red, a stronger color than Holle’s own pale strawberry, he looked relaxed in his own skin, lively, fearless.
“Your first day?” Don asked.
“Yes,” said Holle. “It’s great.”
“Sure it is. That a Scotch accent?”
“Scottish, I-”
“You up to scratch on relativity?”
Her dad had gone through it with her. “Sure.”
“Special relativity is trivial,” Kelly said. “Nothing more than Pythagoras’s theorem. So how are you on your Christoffel symbols?”
“On my what?”
Kelly and Don just laughed, and turned away.
Zane said, “They’re teasing. They’re talking about tensor calculus. The mathematics of general relativity. Which is what you need to describe how spacetime curves around a warp bubble…” He showed her some of Liu’s equations. She recognized derivatives, but some of the symbols were strewn with superscripts and subscripts. “ That is a tensor,” Zane said. “A kind of multidimensional generalization of a vector, which is a quantity with both magnitude and direction-”