Recent observations of gamma rays together with microwaves and polarized radio waves, have detected giant lobes of plasma (Fermi Bubbles) extending above and below the Galactic plane of the Milky Way. These are possible signs of a Nuclear wind powered by either the central black hole or concentrated nuclear star-formation; but our understanding of their origin is hampered by a lack of kinematic information. A unique way to break this deadlock is by using UV spectroscopy of AGN and halo stars lying close on the sky to the Galactic Center to create a systematic absorption line map of diffused entrained gas in the Fermi Bubbles. The variation in absorption properties with Galactic latitude allows us to constrain the physical conditions in the outflowing gas. I will review the status of these unique observational constraints and show that the observed absorption profiles can be explained by a biconical nuclear wind with a radial velocity of ~ 1000 km/sec, and constrain the kinematic age of the Fermi Bubbles to be ~ 6-9 Myrs. These estimates can be used to constrain the minimum mass of UV absorbing gas entrained in the Fermi Bubbles. These observations illustrate the novel use of UV spectroscopy to constrain the feedback processes that regulate galaxy evolution.