String Theoretic Toy Models of the Big Bang

Recently, examples of toy cosmologies have been found that are exact solutions of String Theory. These solutions have the feature that the theoretical framework permits reliable calculation arbitrarily close to the big bang singularity. Thus one can understand both the big bang, and late time physics. I will describe these toy cosmologies, and how they fit into String Theory's chains of equivalences between gravitational and nongravitational theories. These equivalences are the means by which one theoretically probes the big bang.