The concept of a spherical Earth was introduced by the ancient Greeks in the 6th century BCE. Hypotheses about its place in the universe soon followed. Ancient Greek philosophers imagined our motionless planet at the center of the universe, with all the celestial bodies revolving around it in a series of nested, concentric spheres. That theory dominated astronomy until the advent of the Sun-centered Copernican system in the 16th century. According to Aristotle, what moved each planet's sphere?
Back in the day
When Spanish leader Francisco Franco appointed Carrero Blanco to the office of prime minister in 1973, the new premier was expected to uphold Franco's regime—including a plan to eventually restore the Spanish monarchy. Months later, Carrero Blanco was killed by a bomb that exploded under his car as he was leaving mass in Madrid. Though Spain may have moved closer to democracy after Carrero Blanco's death, that was not necessarily the intended goal of the bombing. Who was responsible for it?
Born on a day like today
Abbott was an English theologian, schoolmaster, and author. He wrote educational textbooks, theological works, and a biography of Francis Bacon, and his 1870 Shakespearian Grammar became a permanent fixture of English philology. However, his most famous work is a playfully inventive 1884 novella best described as "mathematical fiction." The humorous and satirical tale has enjoyed an enduring popularity, particularly among mathematicians and students. What is the name of the novella?