Notes: 1  In 1997, MLB retired Jackie Robinson's number 42 meaning no other player in MLB could ever wear it. However, it was grandfathered to anyone who was currently wearing the number. 2  Mariano Rivera is the only Yankee to appear as an active player while wearing his retired number.
The Ordovician Period. The Ordovician Period lasted almost 45 million years, beginning 488.3 million years ago and ending 443.7 million years ago.* During this period, the area north of the tropics was almost entirely ocean, and most of the world's land was collected into the southern supercontinent Gondwana.
The Middle Ages: Between Ancient and Modern. In 476CE, warriors attacked the city of Rome and ended more than 800 years of glory for the âEternal City.â Historians mark this event as the end of ancient history in Western Europe. About one thousand years later, Europe experienced a ârebirthâ we now call the Renaissance.