  We present an exact solution of superstring theory that interpolates in time
between an initial type 0 phase and a final phase whose physics is exactly that
of the bosonic string. The initial theory is deformed by closed-string tachyon
condensation along a lightlike direction. In the limit of large tachyon vev,
the worldsheet conformal field theory precisely realizes the Berkovits-Vafa
embedding of bosonic string theory into superstring theory. Our solution
therefore connects the bosonic string dynamically with the superstring,
settling a longstanding question about the relationship between the two
theories.
