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A 400-YEAR-OLD HOAX? • $1-MILLION PROOF FOR THE SHAPE OF SPACE
JULY 2004
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Mad Cow Disease: Faster Tests, Future Therapies When Methane Ruled Climate Nanosensors Based on Magnetic Effect
COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.
contents july 2004
SCIENTIFIC AMERICAN Volume 291 Number 1
features
ASTRONOMY
50
The Extraordinary Deaths of Ordinary Stars BY BRUCE BALICK AND ADAM FRANK
In five billion years, our dying sun will unfurl into one of the firmament’s premier works of art: a planetary nebula. GENETIC ENGINEERING
62 Gene Doping BY H. LEE SWEENEY
Gene therapy for restoring muscle lost to age or disease is poised to enter the clinic, but elite athletes are eyeing it to enhance performance. INFORMATION TECHNOLOGY
70
Magnetic Field Nanosensors BY STUART A. SOLIN
50 Cat’s Eye nebula
The recently discovered effect called extraordinary magnetoresistance could enable future computer disk drives to have massive capacities and be blazingly fast. ATMOSPHERIC SCIENCE
78
When Methane Made Climate BY JAMES F. KASTING
Today methane-producing microbes are confined to oxygen-free settings, such as the guts of cows, but in Earth’s distant past, they ruled the world. BIOTECHNOLOGY
86
Detecting Mad Cow Disease BY STANLEY B. PRUSINER
New tests can rapidly identify the presence of dangerous prions—the agents responsible for the malady. Several compounds also offer hope for eventual treatment. MATHEMATICS
94
The Shapes of Space BY GRAHAM P. COLLINS
A proof of the century-old Poincaré conjecture helps mathematicians understand three-dimensional space. CRYPTOGRAPHY
104
The Mystery of the Voynich Manuscript BY GORDON RUGG
Cryptographic analysis of a fa