Gilbert Norman Plass (March 22, 1920 – March 1, 2004) was a Canadian physicist who in the 1950s made predictions about the increase in global atmospheric carbon dioxide (CO2) levels in the 20th century and its effect on the average temperature of the planet that closely match measurements reported half a century later.
Clair Cameron Patterson (June 2, 1922 – December 5, 1995) was an American geochemist. Born in Mitchellville, Iowa, Patterson graduated from Grinnell College. He later received his Ph.D. from the University of Chicago and spent his entire professional career at the California Institute of Technology (Caltech).
In collaboration with George Tilton, Patterson developed the uranium–lead dating method into lead–lead dating. By using lead isotopic data from the Canyon Diablo meteorite, he calculated an age for the Earth of 4.55 billion years, which was a figure far more accurate than those that existed at the time, and one that has remained largely unchallenged since 1956.
Patterson first encountered lead contamination in the late 1940s as a graduate student at the University of Chicago. His work on this subject led to a total re-evaluation of the growth in industrial lead concentrations in the atmosphere and the human body, and his subsequent activism was seminal in the banning of tetraethyllead in gasoline and lead solder in food cans.
Georges Lefebvre (French: [ʒɔʁʒ ləfɛvʁ]; 6 August 1874 – 28 August 1959) was a French historian, best known for his work on the French Revolution and peasant life. He is considered one of the pioneers of "history from below". He coined the phrase the "death certificate of the old order" to describe the Great Fear of 1789. Among his most significant works was the 1924 book Les Paysans du Nord pendant la Révolution française ("The Peasants of the North During the French Revolution"), which was the result of 20 years of research into the role of the peasantry during the revolutionary period.