Free Ark by Stephen Baxter Page A

around the extra dimensions, like spiderweb wisps around the hosepipe. That was how the dimensions stayed compact in the first place. And that meant—
    “You can squeeze the hosepipe,” Holle burst out, her imagination racing away.
    Liu turned to her. “And how would you do that, Ms. Groundwater?”
    “With a particle acce—” She stumbled over the word.
    “Accelerator?”
    “Yes. With an accelerator you’re manipulating matter at its smallest levels. You can yank on the tiny strings.”
    Everybody was staring at her. Don and Kelly looked around, Don with amusement, Kelly with something more like resentment.
    “I’m sorry,” she said. “I was thinking out loud.”
    “Don’t be sorry,” Liu said. “You got it about right; that is what we’re planning. We’re setting up a hadron collider outside the city, based on scavenged components from accelerators in the US and overseas. Though we’re still years away from even a ground test the energies required are ferocious . . .” He gestured at the board. “And can you see how that basic concept is expressed in my equations?”
    “No,” she said frankly.
    Kelly laughed. “That figures.”
    But Liu was unperturbed. “That’s not important. Intuition is the thing. But though we have a conceptual design for the creation of the warp bubble, we have a fundamental problem. The energy requirement is literally astronomical. A warp bubble is an artifact of curved space-time analogous in some ways to a black hole. Now, suppose we built a bubble a hundred meters in radius. That should be big enough to house a respectably sized spacecraft, shouldn’t it? Give me an order of magnitude estimate of the mass-energy required.”
    The students huddled over their computers. Kelly muttered, “The radius of a black hole is twice the mass times the gravitational constant divided by speed of light squared . . .”
    “Ten to power twenty-nine kilograms,” Venus Jenning called out. She was a black girl whose family had come from Utah, fleeing the gathering Mormon uprising. As far as Holle could tell she’d figured that number out in her head. Even while she worked, she was reading a yellowing paperback book under her desk, a gaudy science fiction title.
    “Give me that in English,” Liu snapped back. “What does that number mean?”
    Kelly said, “One-tenth the mass of the sun. You’d have to convert one-tenth of all the sun’s mass to energy to be able to build a warp bubble of that size.”
    “Not exactly practical,” Liu said. “And that remains our fundamental problem, after years of studying this concept. We just don’t have the energy resources to build a warp bubble of the size we need.” He drew a big red cross through the equations and diagrams on the board.
    Again Holle found herself thinking out loud. “If the answer’s not the one you want, maybe you’re asking the wrong question.”
    Liu turned to her again.
    “I’m sorry,” she said. “It’s something my dad always says.”
    “Then what is the right question?”
    Zane said quietly, “Maybe, how big a warp bubble can we create?”
    Liu thought that over. “OK. Let’s run with that. What’s the most energetic event humans can control?”
    “Nuclear bombs,” Thomas Windrup called. “Thermonuclear actually.”
    “Right,” Liu said. “And the biggest blast of all was?”
    That sent them scrambling to their computers, and whispering into search engines.
    It was Susan Frasier who came up with the answer. “30th October 1961. A Russian test. Fifty-seven megatons, detonated at Novaya Zemlya.” She smiled, always friendly, always eager to please.
    “All right. And if that mass-energy was applied to creating a black hole?”
    It took them a minute to find out how to convert energy measured in an equivalent tonnage of TNT into joules. This time Kelly made sure she was the first to come up with the final answer. “Its radius would be ten to minus twenty-seven meters.”
    Liu said, “Give me