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.
Dates of the Middle Kingdom of Ancient Egypt. Running from the end of the first intermediate period to the start of the second, the Middle Kingdom lasted from about 2055-1650 B.C.It was composed of part of the 11th Dynasty, the 12th Dynasty, and current scholars add the first half of the 13th Dynasty.1  Predynastic Egypt.ates of the Middle Kingdom of Ancient Egypt. Running from the end of the first intermediate period to the start of the second, the Middle Kingdom lasted from about 2055-1650 B.C.