Portal:Systems science

This list of metro systems includes electrified rapid transit train systems worldwide. In some parts of the world, metro systems are referred to as subways, undergrounds, tubes, mass rapid transit (MRT), métro or U-Bahn. As of 10 April 2026,^[update] 213 cities in 63 countries operate 949 metro lines.

The London Underground first opened as an underground railway in 1863 and its first electrified underground line, the City and South London Railway, opened in 1890, making it the world's first deep-level electric metro system. The Budapest Millennium Underground Railway, which opened in 1896, was the world's first electric underground railway specifically designed for urban transportation and is still in operation today.^{[ISBN missing]} The Beijing Subway is the world's longest metro network at 879 kilometres (546 mi) and the busiest one with annual ridership approximately 2.83 billion passenger trips. As of 2024,^[update] the country with the most metro systems is China, with 54 in operation, including 11 of the 12 longest networks in the world. (Full article...)

The Lorenz attractor is a 3-dimensional structure corresponding to the long-term behavior of a chaotic flow, noted for its butterfly shape. The map shows how the state of a dynamical system (the three variables of a three-dimensional system) evolves over time in a complex, non-repeating pattern.

The attractor itself, and the equations from which it is derived, were introduced by Edward Lorenz in 1963, who derived it from the simplified equations of convection rolls arising in the equations of the atmosphere.

Hendrik Wade Bode (/ˈboʊdi, -də/ BOH-dee, -⁠də, Dutch: [ˈboːdə]; December 24, 1905 – June 21, 1982) was an American engineer, researcher, inventor, author and scientist, of Dutch ancestry. As a pioneer of modern control theory and electronic telecommunications, he revolutionized both the content and methodology of his chosen fields of research. His synergy with Claude Shannon, the father of information theory, laid the foundations for the technological convergence of the Information Age.

He made important contributions to the design, guidance and control of anti-aircraft systems during World War II. He helped develop the automatic artillery weapons that defended London from the V-1 flying bombs during WWII. After the war, Bode, along with his wartime rival Wernher von Braun—who was the developer of the V-2 rocket, and, later, the father of the US space program—served as members of the National Advisory Committee for Aeronautics (NACA), the predecessor of NASA. During the Cold War, he contributed to the design and control of missiles and anti-ballistic missiles. (Full article...)