The Sciences September/October 1996 [antikvár]

I ' ;l ¦ ' ¦ I ' 1 I: ^ 1 ,¦ ' r I \ I ! I ' . , ' ' i ' ' i ' ' I 'ii' 'I,''- ' Initial Conditions EDITOR'S NOTEBOOK It is sobering, in the prime of adult life, to contemplate the likely condition of the vessels that supply one's own heart with blood. Since the landmark cardiovascular study of hundreds of young soldiers killed in the Korean War, heart specialists have known that even in twenty-somethings, chances are the coronary arteries are already stiffening with age and partly blocked with plaque. The process is as insidious as it is painless. Happily, it need not be life threatening. Mair Zamir has closely studied coronary fluid dynamics and, in his article "Secrets of the Heart" (page 26), explains why heart muscle is uniquely vulnerable to vascular disease. More important, his insights offer a novel but compelling reason for taking the trouble to exercise. As I cheer the prowess of Olympic athletes from the comfort of my couch, or leap around the world via my virtual presence on the Internet, my heart beats on without complaint, like a benevolent but permissive parent who can't say no. Its prodigious reserve capacity—presumably built in to meet the extraordinary demands my Stone Age forebears would make on it in preventing some predator from turning them into dinner—can force so much blood through my plaque-lined arteries that no downstream heart-muscle cell is ever moved to hint chat trouble could be brewing. Only when I zap the athletics on television and head to the parks for my ovm run, ride, climb or swim do such cells work hard enough to call for more blood than my network of poor closed vessels can momentarily deliver. Then, assuming the deficit is short lived, my coronary arteries will heed the cellular signals and do what only flesh can: they will grow, regenerate, infiltrate and detour ever more deeply into tissue and around the circulatory blockage. In our cover story for this issue Midori Ashida ponders how best to manage another of the hazards that science has not learned to control, the sudden slippage of the earth. Earthquake predicrion, Ashida argues in "Faulty Premise" (page 15), is a mug's game. Holding out the hope that seismology could one day issue fair warning of coming temblors with the accuracy and timeliness of, say, a weather forecast has too often been just bait to lure public money. The error is not in making available a moderate level of funding for that goal. But, to paraphrase Ashida's essay, let the investment fit the promise. That slogan might well be applied to the subject of "The Fire Next Time," by William J. Hogan, Roger O. Bangerter and Charles P. Verdón (page 20): fusion power. Fusion is the energy source that, as critics of fusion research joke, "is only twenty years away, and always will be." And so one might be excused for raising eyebrows about the projected $1.1 billion the government will spend to build the National Ignition Facility (NIP), a machine designed to reach what fusion specialists call ignition: more energy from the fiasion reactions than goes into turning them on. But such skepticism would be misplaced. After decades of labor and no litde frustration, there is good reason for optimism about the eventual success of fusion power. Two caveats are in order. First, as Hogan et al. point out, radioactive waste generated in a fusion plant would be low level and short lived, provided the walls of the fusion chamber are made of suitable materials to begin with. One cannot countenance construction shortcuts that would give rise to more-dangerous and longer-lived radioactive isotopes. Second, fusion requires tritium, an essential and costly ingredient for making a themionuclear explosive. Suitable safeguards against the unintended distribution of tritium must be maintained. With those caveats, it makes sense to support the next step in the research effort on fusion power. With the end of the cold war, work on the understanding of fusion processes has gotten a substantial boost from declassification. Within a factor of two (down from a factor of 1,000), it is now known how much energy will be needed to achieve ignition. The NIP and its French counterpart, the Mégajoule laser project, are Hkely to pull off just what they have set out to do: no mean accomplishment, given the history of the business of making energy "too cheap to meter." —Peter G. Brown 2 the sciences • Seplember/Oclohcr 1996