The Short, Rich Life of Positronium

Jens Zorn
1999; Bronze; Sculpture
Central Campus; Coutryard between Randall Laboratory and West Hall

Gift of the Department of Physics, University Administration, and family and friends of Arthur Rich. Professor of Physics Jens Zorn created this piece to “commemorate the fundamental research on anti-matter done at the University of Michigan by [professor] Arthur Rich and his students and colleagues; it is thus a visual reminder of some of the most important physics done on our campus…a celebration of achievement perhaps more than a visual eulogy of an individual.” Positrons, which are created only under special circumstances of atomic and nuclear interactions, are attracted and coupled to electrons “in a mutually encircling, ever-decreasing orbit. This two-body system is called ‘positronium’ and resembles an ordinary atom…During its short lifetime (only a few millionths of a second), the positronium emits light as its orbit shrinks. Finally, the positron and electron annihilate one another as they convert to two high energy gamma rays in the purest known example of Einstein’s famous relationship of mass to energy: E=mc².” U-M physicists, initially Arthur Rich, have studied the formation and annihilation of positronium since 1965. Prof. Zorn is also the sculptor of G-2 (gee-minus-two), located nearby.