Defining Characteristics of Cross-Sectional Studies. Think of a cross-sectional study as a snapshot of a particular group of people at a given point in time. Unlike longitudinal studies that look at a group of people over an extended period, cross-sectional studies are used to describe what is happening at the present moment.
Dec. 3, 1992: The first text message Papworth, a former developer at Sema Group Telecoms, sends the world's first SMS greeting to his friend Richard Jarvis, who at the time worked at U.K. service Vodafone. Jarvis couldn't say Merry Christmas back, because his brick-sized Orbitel 901 phone had no way of inputting text.
Bitcoin was invented by Satoshi Nakamoto, who published the invention on 31 October 2008 in a research paper called Bitcoin: A Peer-to-Peer Electronic Cash system. It was implemented as open source code and released in January 2009. Bitcoin is often called the first cryptocurrency although prior systems existed.