Number 158 (Story #3), December 30, 1993 by Phillip F. Schewe and Ben Stein THE CONNECTION BETWEEN CHAOS AND GENERAL RELATIVITY was the subject of a workshop in July in Alberta, Canada. Just as the nonlinear equations governing fluid flows lead to chaotic conditions, so Einstein's nonlinear equations governing spacetime are expected to lead to chaotic behavior, particularly in the vicinity of strong gravitational fields. For example, Matthew Choptuik of the University of Texas reported studies of how light waves might collapse into black holes. David Hobill of the University of Calgary and others are adapting the "Mixmaster universe" theory---a model in which the universe at certain times may be expanding in some directions and contracting in others---in an effort to study localized behavior, such as gravitational collapse or the origin of galaxies. One obstacle faced by these researchers is that a good definition of time, necessary in following the extreme sensitivity of chaotic systems to the specification of boundary conditions, is problematic in the warped spacetime described by general relativity. Therefore Richard Churchill of Hunter College is seeking "to figure out a definition of chaos that doesn't include time." (Science News, 4 Dec.)