At age 27:
Kurt Vonnegut, Jr. dropped out from his job at General Electric to become a full-time writer.
Henry David Thoreau went off for two years to live alone in a cabin at Walden Pond.
Cosmonaut Yuri Gagarin became the first person in space.
Memphis millionaire Frederic W. Smith, whose father built the Greyhound bus system, founded Federal Express.
Scottish botanist David Douglas discovered the Douglas fir.
Ernest Hemingway published his first novel, The Sun Also Rises.
Boston dentist William Morton pioneered modern anaesthesiology after learning that inhalation of ether will cause a loss of consciousness.