[1][2] When he retired from teaching at the age of 104 in 2004, Crist is widely believed to have been America's oldest worker at the time.

He joined the Manhattan Project in 1941 and was among the leading scientists who developed the critical initial step of the separation of uranium isotopes.

As a voluntary educator, Crist pursued his mission of introducing today's students, especially non-science majors, to the impact of science and technology on culture and the environment.

The results of these experiments appeared in twenty-seven journal articles and were reported at ten international conferences.

His academic achievements and his overcoming the challenges of aging were recognized by numerous events and awards such as America's Outstanding Older Worker (2002), the PBS series The Living Century in the episode "A Teacher and Student for Life", and the editorial "Phytoremediation's Centenarian" (International Journal of Phytoremediation, 2002), as well as extensive additional press and television coverage both in the United States and abroad.