Scientific American (may 2004)

TRANSIT OF VENUS: FIRST IN 122 YEARS • SCIENCE REVIVES FREUD Using DNA to Program Synthetic Living Machines MAY 2004 WWW.SCIAM.COM The Big Bang Might Not Have Been the Beginning Do Fuel Cells Make Environmental Sense? The Pervasive Future of Better GPS COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. $4.95 contents may 2004 SCIENTIFIC AMERICAN Volume 290 Number 5 features COSMOLOGY 54 The Myth of the Beginning of Time BY GABRIELE VENEZIANO String theory suggests that the 13.7-billion-year-old universe we know is only part of an infinite expanse that predates the big bang. ENERGY 66 Questions about a Hydrogen Economy BY MATTHEW L. WALD Fuel cells are generating excitement as clean alternatives for powering automobiles. But the environmental benefits of shifting to a hydrogen-based economy are cloudy. BIOTECHNOLOGY 74 Synthetic Life BY W. WAYT GIBBS Biologists have tinkered with the genes inside organisms for decades. Now, with “circuits” of interacting DNA, they are beginning to create programmable living machines. NEUROSCIENCE 82 Freud Returns BY MARK SOLMS Modern biological descriptions of the brain may fit together best when integrated with Freud’s controversial psychological theories. Also: Counterpoint from J. Allan Hobson, who argues that Freud’s thinking is still highly suspect. 54 Are time and space older INFORMATION TECHNOLOGY 90 than the big bang? Retooling the Global Positioning System BY PER ENGE GPS units already serve more than 30 million users, from hikers to airline pilots. The next wave of improvements will make the technology even more accurate, reliable, useful and ubiquitous. PLANETARY SCIENCE 98 The Transit of Venus BY STEVEN J. DICK When Venus crosses the