 According to Gasperini (2008), string cosmology’s prediction of a pre-big-bang universe results from a principled application of symmetry principles. Furthermore, string theory has a built in mechanism (namely a minimum string length) that seems to rule out singularities of infinite curvature or spatial length shrinking to zero. As was the case in LQC, the values of physical quantities in string theory are constrained by quantum mechanical laws; and so some quantities that grew beyond bounds in classical theory are well-behaved in quantized versions of that theory.