Abstract

A strangelet is a small piece of strange quark matter, which consists of roughly equal numbers of u, d, and s quarks. Some have said that strange quark matter could be more stable than ordinary nuclear matter for which the quarks are collected into groups of three as neutrons and protons. At a time when our understanding was largely qualitative it was suggested that a single strangelet could grow without limit by absorbing ordinary nuclei. This raised fears that making a single strangelet in a high energy accelerator could result in the destruction of the earth. Improved theory supplemented with additional experiments, have removed all justification for such catastrophic scenarios. Calculations of color-flavor locking allow for a number of variations of strange quark matter, some of which have a lower energy than any other arrangement of quarks. Such material might be found inside of neutron stars for which the necessary pressure and low temperature are available. Those calculations that predict a density larger than that of compressed neutrons have been ruled out by the recent observation of a neutron star with a mass 2.0 times the mass of the sun.