Title: What Made the Big Bang so Big: Testing Physics With the
        Cosmic Microwave Background

Abstract:

The cosmic microwave background (CMB) serves as a "backlight" throughout
the evolution of the universe, encoding details of physics at energies up
to a trillion times higher than any accessible to particle accelerators. 
New instrumentation now offers the tantalizing possibility of detecting the
"smoking gun" signature of primordial inflation through its imprint on the
linear polarization of the microwave background. A positive detection would
have profound consequences for both cosmology and high-energy physics.  It
would not only establish inflation as a physical reality, but would probe
physics at energies approaching Grand Unification. I will present the
scientific motivation behind measurements of the CMB polarization and
discuss how recent experimental progress could lead to a detection in the
not-very-distant future.