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 is both a cryptocurrency and an electronic payment system invented by an unidentified programmer, or group of programmers, under the name of Satoshi Nakamoto. Bitcoin was introduced on 31 October 2008 to a cryptography mailing list, and released as open-source software in 2009. The identity of Nakamoto remains unknown, though many have claimed to know it. The system is peer-to-peer, and transactions take place between users directly, without an intermediary.