With the first direct detection of gravitational waves, the LIGO detectors have opened a new field of astrophysics, discovered a new class of massive stellar mass black holes, and enabled tests of general relativity. To make these discoveries, we built the most sensitive displacement meters yet, measuring displacements of one thousandth of a proton diameter over a 4 kilometer baseline. This talk will focus on the physics of the ground breaking detectors, and the possibilities for extending their reach. One of the most promising techniques for improving the sensitivity is the use of squeezed states to reduce quantum noise. l will describe a test of squeezing in the LIGO interferometers, and implications for the permanent application of squeezing in Advanced LIGO over the next few years. Because gravitational wave detectors measure amplitude rather than power, improvements in sensitivity from squeezing, cryogenic operation and new optical materials have the potential to dramatically increase the volume of the universe which can be surveyed. In a new and larger facility, LIGO style detectors could observe compact object binaries from the earliest periods of star formation, making complete surveys at distances difficult to observe with optical telescopes.