  In a universe whose elementary constituents are point particles there does
not seem to be any obvious mechanism for avoiding the initial singularities in
physical quantities in the standard model of cosmology. In contrast in string
theory these singularities can be absent even at the level where spacetime is
treated classically. This is a consequence of the basic degrees of freedom of
strings in compact spaces, which necessitate a reinterpretation of what one
means by a very small universe. We discuss the basic degrees of freedom of a
string at the classical and quantum level, the minimum size of strings (string
uncertainty principle), the t-duality symmetry, and string thermodynamics at
high energy densities, and then describe how these considerations suggest a
resolution of the initial singularity problem. An effort has been made to keep
this writeup self-contained and accessible to non-string theorists.
