The excitement of learning separates youth from old age. As long as you're learning you're not old.
Source: Women and the Nobel Prize, by Barbara Shiels, 1985.
-- Rosalyn Sussman Yalow, (Jul 19 1921-2011), US medical physicist; She developed the radioimmunoassay to measure amounts of biological substances in the body; second woman to win the Nobel Prize in medicine, 1977.