- The Lost Generation is the demographic cohort that reached early adulthood during World War I, and preceded the Greatest Generation. The social generation is generally defined as people born from 1883 to 1900, coming of age in either the 1900s or the 1910s. The term is also particularly used to refer to a group of American expatriate writers living in Paris during the 1920s. Gertrude Stein is credited with coining the term, and it was subsequently popularised by Ernest Hemingway, who used it in the epigraph for his 1926 novel The Sun Also Rises: “You are all a lost generation.” “Lost” in this context refers to the “disoriented, wandering, directionless” spirit of many of the war’s survivors in the early postwar period.
- Klein bottle (Wikipedia)
In mathematics, the Klein bottle (/ˈklaɪn/) is an example of a non-orientable surface; that is, informally, a one-sided surface which, if traveled upon, could be followed back to the point of origin while flipping the traveler upside down. More formally, the Klein bottle is a two-dimensional manifold on which one cannot define a normal vector at each point that varies continuously over the whole manifold. Other related non-orientable surfaces include the Möbius strip and the real projective plane. While a Möbius strip is a surface with a boundary, a Klein bottle has no boundary. For comparison, a sphere is an orientable surface with no boundary.
- Greatest Generation (Wikipedia)
The Greatest Generation, also known as the G.I. Generation and the World War II Generation, is the demographic cohort following the Lost Generation and preceding the Silent Generation. The social generation is generally defined as people born from 1901 to 1927. They were shaped by the Great Depression and were the primary generation composing the enlisted forces in World War II. Most people of the Greatest Generation are the parents of the Silent Generation and Baby Boomers, and, in turn, are the children of the Lost Generation.