From Tony Cheney Perhaps an explanation for the anomalous velocity of neutrinos from CERN to Gran Sasso in Italy (1 October, p6), compared with the velocity of light in a vacuum, depends on what you mean by a vacuum. Measurements of the speed of light in a vacuum may have a hidden error. We all know these days that the vacuum is not empty - it is an energy field seething with virtual particles. Perhaps light, when ploughing through the vacuum, is slower by 60 billionths of a second than neutrinos covering the same distance. Since neutrinos can zip through Earth as if it weren't there, the quantum vacuum isn't going to bother them much. Risky business From John Baker So, scientists in Italy are being prosecuted for failing to predict an earthquake (24 September, p 34). May I predict the number of prosecutions relating to other failures of risk management? Investment bankers in charge of disaster banks - no prosecutions; any public servants (other than scientists), for anything - none; politicians responsible for lax financial regulation, overspending and free credit - none; politicians, for misusing evidential and statistical information - none. Now that's what I call predictable. Chalfont St Giles, Buckinghamshire, UK that, because we are getting less and less of our nutrition from the marine food web, our brain capacity could diminish over several generations. Brain essentials From Michael Crawford, Imperial College London Your article "A brief history of the brain" (24 September, p 40) was wonderful, but missed an important point. During its first 2.5 billion years, life was largely anaerobic. It is likely that during this phase, synthesis of docosahexaenoic acid (DHA) would have been limited. DHA is a major essential fatty acid constituent of the photoreceptor and the brain. Its synthesis requires six oxygen atoms just to introduce six double bonds on top of the other high-energy requirements for fat synthesis. Snap the theory? From Richard Snell My interest in the account of the thoughts of cosmologist Max Tegmark was tempered by something more than surprise -I learned that the rejection of the early cosmic inflation or of the Copernican principle, that Earth does not occupy a special place in the universe, "are anathema to cosmology", (24 September, p 8). The tenor of opinions seemed consistent with the basis of scientific thought - that no hypothesis is above challenge and change in the light of subsequent discovery. If "anathema" is now considered appropriate to scientific discussion in certain circumstances, then it must have a meaning quite different to its current definition.
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