Abstract - McKay A large amount of recent theoretical and experimental work has shown that gravitational lensing effects afford our best opportunity to directly measure the abundance and distribution of total mass in the universe. Recent work has extended the measurement of mass distributions from the strong lensing regime of multiple quasar images and giant arcs to the weaker lensing effects seen in the periphery of massive clusters of galaxies. With the unique wide field imaging system of the Sloan Digital Sky Survey (SDSS), it will be possible to extend such lensing studies to very wide fields, and study density variations in the universe independent of the bias between luminous and dark matter. The weak lensing technique is the only way to directly probe large scale structures in the mass density of the universe, and the SDSS offers the only opportunity to do this over a large fraction of the sky. These methods will be used to measure the surface density of matter over one fourth of the sky, to probe the evolution of this density field using photometric and spectroscopic redshifts, to measure directly the bias between the observed local distribution of luminous matter and the underlying mass distribution, and to measure the lensing mass of nearby clusters like the Coma cluster. This is a difficult program, requiring careful control of systematic errors, but the SDSS is exceedingly well designed to meet these challenges. A complementary program would search for quasar lenses within the SDSS data for use in related studies. Data generated by the SDSS will be used both for traditional graduate and undergraduate research, and also as a tool for bringing current research into the introductory classroom. Advanced undergraduate students will be involved in designing a set of tools, using the SDSS data, to illustrate important scientific principles. These tools will be used in a "hands-on" cosmology class for entering non-science majors, in large standard intro ductory physics classes, and will be distributed through existing teacher outreach programs. There will be continued efforts to improve the quality of standard undergraduate teaching at the University of Michigan, and to continue SDSS public information programs and a successful public lecture series. This project is a five year program that will enable a faculty member at the University of Michigan to develop further as an astrophysics researcher and an educator. The grant will support the faculty member, a graduate student, and a number of undergraduates in their analysis of gravitational lensing effects in data to be obtained by the Sloan Digital Sky Survey. There is also support to use the SDSS data in the development of new educational materials for use in a variety of classroom situations.
