Contemporary history describes the period timeframe that is closely connected to the present day; it is a certain perspective of modern history. The term "contemporary history" has been in use at least since the early 19th century. In the widest context of this use, contemporary history is that part of history still in living memory. Based on human lifespan, contemporary history would extend for a period of approximately 80 years. In a narrower sense "contemporary history" may refer to the history remembered by most (more than 50 percent) of human beings alive, extending to about a generation. As the median age of people living on Earth is 30 years as of the present this is currently often understood as meaning anything after about 1991 when the Cold War order collapsed and use of the Internet became widespread outside of academia, defense and big business; the beginning of the "long 21st century".