The 3-Helium Problem: 
Constraining the Chemical Evolution of the Milky Way

Tom Bania, Boston University

The study of the origin and evolution of the elements is one of the
cornerstones of modern astrophysics. For any given isotope it is
crucial to determine its abundance and how that abundance varies
temporally and spatially. Knowing the cosmic abundance of the 3-He
isotope has a broad interdisciplinary impact: 3-He can be used to test
the theory of stellar nucleosynthesis; 3-He gives important
information needed to evaluate models of Galactic chemical evolution;
3-He can help constrain Big Bang Nucleosynthesis.  I shall discuss the
current status and astrophysical implications of our long term study
of the 3-He abundance in Galactic H II regions and planetary nebulae
using measurements of the 3-He hyperfine "spin-flip" transition.