Letters.Matters of flavor "Physics bedrock cracks, sun shines in" (SN: 6/23/01, p. 388) says that solar neutrinos neu·tri·no (n  -tr  n )n. pl. oscillate 1. To swing back and forth with a steady, uninterrupted rhythm. 2. To vary between alternate extremes, usually within a definable period of time. os cil·la tor n.os between different flavors on
the trip to Earth and that those taking a longer path have more time to
oscillate into kinds of neutrinos that the sun doesn't produce. Do
the scientists note a variation in neutrino types based on the
eccentricity eccentricity, in astronomy: see orbit. of Earth's orbit? When Earth is closest to the sun,
electron neutrinos would have less time to oscillate.
Douglas Nelson Salt Lake City, Utah About 7 percent fewer solar neutrinos hit detectors when Earth is furthest from the sun, compared with when it's closest, says Arthur B. McDonald, director of the Sudbury Neutrino Observatory in Ontario. However, whether the Earth-sun distance also influences the oscillation of the sun's electron neutrinos into other flavors remains unknown. "It is something we will analyze for in the future, "McDonald says. --P. Weiss Not so clear cut The article "Amazon forest could disappear, soon" (SN: 7/14/01, p. 24) says, "Logging and burning for agriculture currently claim about 1 percent of the Amazon rain forest rain forest: see forest. per year." This simply is not true. We have been hearing this and even more alarming "statistics" about Amazon deforestation (programming) deforestation - A technique invented by Phil Wadler for eliminating intermediate data structures built and passed between composed functions in function languages. for more than 20 years. Yet NASA Landsat images show that little more than 10 percent of the original forest has been cleared. Even if the clearing has been going on for only those 20 years (and it has been proceeding for far longer than that), this amounts to but half of the rate claimed. The facts are, to be sure, troubling, but you do a disservice to those making reasonable efforts to curtail the clearing by restating exaggerated and discredited numbers. G.A. Esworthy Apes, N.C. Current Landsat images show that about 15 percent of the rain forest in Brazil, which makes up 80 percent of the Amazon rain forest, has been deforested, says Mark Cochrane, a research scientist at Michigan State University in East Lansing. Each year about 0.5 percent of the rain forest there is lost to burning, agriculture, or logging. Nearly an equal amount is substantially degraded by human activity, Cochrane says. Outside Brazil, at least 0.4 percent of the South American rain forest was lost each year between 1986 and 1992. That's the period for which the most recent estimates are available, says Kip Desch, manager of the Deforestation Mapping Group at the University of Maryland's Global Land Cover Facility. --S. Perkins |
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