This talk will be in two parts.  First I will describe the Green Bank Telescope, a 100-meter diameter radio telescope that is one of the largest moving objects on land, and, owing to recent upgrades, is now our largest mm-wave radio telescope.  I'll discuss its unusual origin, its capabilities, and topics from some of its recent scientific programs including the search for gravitational radiation, Mercury's molten core, interstellar anions, and the growth and evolution of galaxies.

The second part of the talk will continue the topic of growth and evolution of galaxies, with a focus on the Milky Way.  Several lines of evidence indicate that our Galaxy must have been accreting low metallicity gas at the rate of about 1 solar mass per year for a substantial portion of its life, but the details of this process are unclear as is the origin of the fresh material.  Observations in the 21cm Hydrogen line have recently found a dramatic example of this process in action in the form of a cloud with more than a million solar masses of gas on a trajectory to intersect the Milky Way disk in a few tens of million years.  I will discuss this object and the information it gives us on evolution of the Galaxy, the structure of the gaseous halo,and its possible relationship to dark matter halos.