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NAUTILUS EDUCATION | BETA PRODUCT Going Dark: Scavenging Exotic Matter Instead of scavenging hydrogen gas, Jia Liu, a physics graduate student at New York University, has pro- posed foraging for dark matter, the invisible exotic material that astronomers think makes up the bulk of the galaxy. Particle physicists hypothesize that dark matter consists of a type of particle called the neutralino, which has a useful property: When two neutralinos collide, they annihilate each other in a blaze of gamma rays. Such reactions could drive a ship forward. Like the hydrogen scooper, a dark-mat- ter ship could approach the speed of light. The prob- lem, though, is that dark matter is dark—meaning it doesn’t respond to electromagnetic forces. Physicists know of no way to collect it, let alone channel it to produce rocket thrust. If engineers somehow overcame these problems and built a near-light-speed ship, not just Alpha Cen- tauri but the entire galaxy would come within range. In the 1960s astronomer Carl Sagan calculated that, if you could attain a modest rate of acceleratton—about the same rate a sports car uses—and maintain it long enough, you’d get so close to the speed of light that you’d cross the galaxy in just a couple of decades of shipboard time. As a bonus, that rate would provide a comfortable level of artificial gravity. On the downside, hundreds of thousands of years would pass on Earth in the meantime. By the time you got back, your entire civilization might have gone ape. From one perspective, though, this is a good thing. The tricks relativity plays with time would solve the eter- nal problem of too-slow computers. If you want to do some eons-long calculation, go off and explore some distant star system and the result will be ready for you when you return. The starship crews of the future may not be voyaging for survival, glory, or conquest. They may be solving puzzles. Going Warp: Bending Time and Space With a ship moving at a tenth the speed of light, humans could migrate to the nearest stars within a lifetime, but crossing the galaxy would remain a jour- ney of a million years, and each star system would still be mostly isolated. To create a galactic version of the global village, bound together by planes and phones, you'd need to travel faster than light. 10 Contrary to popular belief, Emstein’s theory of rela- tivity does not rule that out completely. According to the theory, space and time are elastic; what we perceive as the force of gravity is in fact the warping of space and time. In principle, you could warp space so severely that you'd shorten the distance you want to cross, like fold- ing arug to bring the two sides closer together. If so, you could cross any distance instantaneously. You wouldn’t even notice the acceleration, because the field would zero out g-forces inside the ship. The view from the ship windows would be stunning. Stars would change in col- or and shift toward the axis of motion. It seems almost mean-spirited to point out how far beyond our current technology this idea is. Warp drive would require a type of material that exerts a gravita- tional push rather than a gravitational pull. Such mate- rial contains a negative amount of energy—literally less than nothing, as if you had a mass of —50 kilograms. Physicists, inventive types that they are, have imagined ways to create such energy, but even they throw up their hands at the amount of negative energy a starship would need: a few stars’ worth. What is more, the ship would be impossible to steer, since control signals, which are restricted to the speed of light, wouldn’t be fast enough to get from the ship’s bridge to the propulsion system located on the vessel’s perimeter. (Equipment within the ship, however, would function just fi When it comes to starships, it’s best not to get hung up on details. By the time humanity gets to the point it might actually build one, our very notions of travel may well have changed. “Do we need to send full humans?” asks Long. “Maybe we just need to send embryos, or maybe in the future, you could completely download yourself into a computer, and you can remanufacture yourself at the other end through something similar to 3-D printing.” Today, a starship seems like the height of futuristic think- ing. Future generations might fi itquamt. © george musser is a writer on physics and cosmology and authorof The Complete Idiot's Guide ToString Theory(Alpha, 2008). He was a senior editor at Scientific American for 14 years and has won honors such as the American Institute of Physics Science Writing Award. HOUSE_OVERSIGHT_015471