CANCER-KILLING VIRUSES • DANGEROUS MELTING IN THE ARCTIC China: The Next Space Superpower OCTOBER 2003 WWW.SCIAM.COM Star Clusters Born of Galactic Collisions The Economics of Child Labor Protecting Farms against Agricultural Terrorism — see page 20 COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC. $4.95 contents october 2003 SCIENTIFIC AMERICAN Volume 289 Number 4 features ASTRONOMY 46 The Unexpected Youth of Globular Clusters BY STEPHEN E. ZEPF AND KEITH M. ASHMAN Globular star clusters were thought to be the stodgy old codgers of the universe, but many, in fact, are young. MATERIALS 52 Artificial Muscles BY STEVEN ASHLEY New polymers that act like electrically controlled muscles could power robots and prosthetic limbs, replace speaker diaphragms and literally change the shape of aviation. ENVIRONMENT 60 Meltdown in the North BY MATTHEW STURM, DONALD K. PEROVICH AND MARK C. SERREZE Sea ice and glaciers are melting, permafrost is thawing, tundra is yielding to shrubs. How will it all affect the Arctic— and the rest of the planet? BIOTECHNOLOGY 68 Tumor-Busting Viruses BY DIRK M. NETTELBECK AND DAVID T. CURIEL Researchers are investigating treatments for cancer that would infect the body with viruses lethal only to tumor cells. HUMAN SPACEFLIGHT 76 China’s Great Leap Upward 52 Robot walks using artificial muscles BY JAMES OBERG How China hopes to become the newest space superpower. ECONOMICS 84 The Economics of Child Labor BY KAUSHIK BASU Campaigns against child labor work better when they combine the long arm of the law with the invisible hand of the marketplace. www.sciam.com SCIENTIFIC AMERICAN COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC. 5 SCIENTIFIC AMERICAN Volume 289 Number 4 departments 8 SA Perspectives Biotechnology even Europe can love. 10 10 12 18 20 How to Contact Us On the Web Letters 50, 100 & 150 Years Ago News Scan ■ ■ ■ ■ ■ ■ ■ ■ 101 103 42 Staking Claims Gaps in defending food against terrorism. Sexuality research ducks a conservative budget ax. The race to find the superconductivity state. Play it again: Treating musicians’ repetitive stress. Mapping the earth’s gravity. Flaws in studies of hormone replacement therapy? By the Numbers: Interracial marriages. Data Points: Fast-cracking crust. 38 Innovations A serendipitous discovery could provide engineers with a dream material: inexpensive titanium. 44 If the patent office needs a good, sharp kick, this tinkerer can provide it. 44 Insights Pekka Haavisto of the United Nations worries about the environmental impact of Gulf War II. 92 Working Knowledge Smart fabrics for smart athletes. 94 Technicalities The world’s largest video arcade could fit in your living room. 98 Reviews Small Things Considered explores the trade-offs that make all designs imperfect. Pekka Haavisto columns 43 Skeptic BY MICHAEL SHERMER One hundred and six billion arguments against immortality. 101 Puzzling Adventures BY DENNIS E. SHASHA Strategic bullying. 102 Anti Gravity BY STEVE MIRSKY Later, ’gator. 103 Ask the Experts What causes insomnia? Why is the sky blue? 104 Fuzzy Logic BY ROZ CHAST Cover image by Kenn Brown; SRI International (preceding page); Kate Brooks (left) Scientific American (ISSN 0036-8733), published monthly by Scientific American, Inc., 415 Madison Avenue, New York, N.Y. 10017-1111. Copyright © 2003 by Scientific American, Inc. All rights reserved. No part of this issue may be