E-Book Content
GENETIC FUTURE OF CROPS • VIRTUAL REALITY BEATS FEAR AND PAIN The Pros and Cons of New Bunker-Busting Nuclear Missiles
AUGUST 2004 WWW.SCIAM.COM
Who needs rockets? Power and thrust from 25 miles of cable in space
DYING FOR A DRINK Arsenic in Well Water Threatens Millions LAWRENCE M. KRAUSS On the Questions That Plague Physics
COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.
contents august 2004
SCIENTIFIC AMERICAN Volume 291 Number 2
features
BIOTECHNOLOGY
42
Back to the Future of Cereals BY STEPHEN A. GOFF AND JOHN M. SALMERON
Marrying traditional plant breeding with genetic insights, a technology called marker-assisted breeding could help launch a new green revolution. SPACEFLIGHT
50 Electrodynamic Tethers in Space
42 Better rice through smarter breeding
BY ENRICO LORENZINI AND JUAN SANMARTÍN
By exploiting fundamental physical laws, tethers may provide low-cost electrical power, thrust, drag, and artificial gravity for spaceflight. MEDICAL TREATMENTS
58
Virtual-Reality Therapy BY HUNTER G. HOFFMAN
Patients can get relief from pain or overcome their phobias by immersing themselves in computer-generated worlds. NUCLEAR WEAPONS
66
Nuclear Bunker Buster Bombs BY MICHAEL LEVI
New burrowing nuclear weapons could destroy subterranean military facilities—but their strategic and tactical utility is questionable. INFORMATION TECHNOLOGY
74
Next Stretch for Plastic Electronics BY GRAHAM P. COLLINS
Organic semiconductor devices can make more than just bendable displays. They will find use in wearable electronics and innumerable other applications. COSMOLOGY
82
Questions That Plague Physics A CONVERSATION WITH LAWRENCE M. KRAUSS
The physicist and best-selling author discusses th