In the New Scientist of 5 July 2008 is an article 'Crucible of Creation' on pp 28 - 31. Part of it concerns the ratio of the isotopes Li-6 and Li-7 which formed just after the Big Bang. They discuss the work of Maxim Pospelov of the Perimeter Institute in Waterloo, Ontario. Pospelov proposes that the Li-6/Li-7 ratio was affected by the presence of the stau, supersymmetric partner of the tau lepton, which catalysed fusion reactions involving beryllium-7 with protons (thereby preventing much Be-7 from decaying to Li-7, instead converting it to He-4 via B-8); and later of helium-4 with deuterons to give lithium-6. This latter reaction is said to have taken place THREE HOURS after the Big Bang. Therefore the stau must have a half-life of the order of hours, far longer than that of any other unstable particle. Why is this thought possible or likely? To what would the stau decay? Such a long-lived particle must surely form in energetic cosmic-ray reactions. It should be far more penetrating than the similarly charged muon, because of its great mass. So why hasn't it already been found? - for example in experiments in deep mines looking for proton-decay or cosmic neutrinos.