  Technical discussions of the Laser Interferometer Gravitational Wave
Observatory (LIGO) sensitivity often focus on its effective sensitivity to
gravitational waves in a given band; nevertheless, the goal of the LIGO Project
is to ``do science.'' Exploiting this new observational perspective to explore
the Universe is a long-term goal, toward which LIGO's initial instrumentation
is but a first step. Nevertheless, the first generation LIGO instrumentation is
sensitive enough that even non-detection --- in the form of an upper limit ---
is also informative. In this brief article I describe in quantitative terms
some of the science we can hope to do with first and future generation LIGO
instrumentation: it short, the ``science reach'' of the detector we are
building and the ones we hope to build.
