The Kerala school of astronomy and mathematics in India flourished between the 14th and 16th centuries. Kerala scholars discovered a procedure for determining the position of the Moon every 36 minutes and methods for estimating the movement of the planets. While attempting to solve astronomical problems, the scholars independently created a number of important mathematical concepts, centuries before the invention of calculus in Europe. What was their most important discovery?
Back in the day
The Berlin Wall was erected in 1961 by the East German government and later extended along the entire border between East and West Germany. Built to prevent defections, it became a symbol of the Cold War. In 1987, US President Reagan visited Berlin to commemorate the city's 750th anniversary and used his speech to publicly challenge Gorbachev to destroy the wall. Two years later, it was dismantled in a failed bid by the Communists to retain power. Why did some Reagan staffers oppose his speech?
Born on a day like today
Adams, a Pulitzer Prize-winning American photographer and photojournalist noted for his war coverage and portraits of celebrities and politicians, began his career as a combat photographer during the Korean War. His best known photograph, a harrowing image of the moment that South Vietnamese police chief Nguyen Ngoc Loan executed a Vietcong prisoner, Nguyen Van Lem, on a Saigon street in 1968, won the Pulitzer Prize. Why did he later apologize to the police chief for having taken the picture?