Stardust Memories: Tiny Records of Galactic History DECEMBER 2000 $4.95 WWW.SCIAM.COM Nanotubes: the Future of electronics PROTEIN CLUES TO ALZHEIMER’S Controlling Urban Sprawl Rulers of the Jurassic Seas The reiGn of icHthyosaurs Copyright 2000 Scientific American, Inc. Volume 283 www.sciam.com Number 6 COVER STORY Rulers of the Jurassic Seas 52 Contents December 2000 Ryosuke Motani Fish-shaped reptiles called ichthyosaurs reigned over the oceans for as long as dinosaurs roamed the land. Only recently have paleontologists discovered why these amazing monsters were so successful. Nanotubes for Electronics Philip G. Collins and Phaedon Avouris These threadlike macromolecules are stronger than steel, but the immediate uses for them have nothing to do with strength. Their greatest value may be in faster, more efficient and more durable electronic devices. 62 The Secrets of Stardust J. Mayo Greenberg 70 Tiny grains of dust floating in interstellar space have radically altered the history of our galaxy. They also carry a record of the Milky Way’s past. The Science of Smart Growth 84 Donald D. T. Chen Are there alternatives to urban sprawl? While pundits and pols debate the issue, studies in the real world point to better ways of organizing communities. TRENDS IN PHYSICS The Coolest Gas in the Universe 92 Graham P. Collins, staff writer The bizarre quantum vapors called Bose-Einstein condensates exist at temperatures just above absolute zero. Nevertheless, they are one of the hottest topics in experimental physics. 5 Copyright 2000 Scientific American, Inc. Contents December 2000 Volume 283 www.sciam.com Number 6 Piecing Together Alzheimer’s 76 Peter H. St George-Hyslop The stunningly complex biochemical puzzle that underlies this crippling disease remains incomplete, but parts that seemed unrelated just a decade ago are now fitting into place and offer prospects for treatments. 8 FROM THE EDITORS LETTERS TO THE EDITORS 10 50, 100 & 150 YEARS AGO 14 PROFILE 38 Computer scientist Lynn Conway reveals her secret work as a man. TECHNOLOGY & B USINESS 44 After flying high with the military, telesurgery lands hard. Q&A: Operating by remote control? CYBER VIEW 50 Why the U.S. doesn’t get digital radio. WORKING KNOWLEDGE 100 Disposable diapers. THE AMATEUR SCIENTIST 102 by Shawn Carlson Calibrating a thermometer. MATHEMATICAL RECREATIONS by Ian Stewart Counting the gaps between primes. 106 1 2 1 2 3 16 17 31 32 2 4 5 6 18 19 20 33 34 35 2 4 7 8 9 21 22 23 24 36 37 38 39 4 6 4 108 BOOKS Did you hear the one about Laughter: A Scientific Investigation? Also, The Editors Recommend. 113 WONDERS by the Morrisons The enduring luster of gold, silver and copper. CONNECTIONS by James Burke 114 ANNUAL INDEX 2000 117 ANTI GRAVITY by Steve Mirsky 120 N E W S & A N A LY S I S 16 The next hurdle for RU 486. 16 A prehistoric smokehouse. 26 Hacking for Uncle Sam. 20 Plastic competition for silicon. 22