- published: 08 May 2016
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A closed system is a physical system that does not allow certain types of transfers (such as transfer of mass) in or out of the system. The specification of what types of transfers are excluded varies in the closed systems of physics, chemistry or engineering.
In nonrelativistic classical mechanics, a closed system is a physical system that doesn't exchange any matter with its surroundings, and isn't subject to any force whose source is external to the system. A closed system in classical mechanics would be considered an isolated system in thermodynamics.
In thermodynamics, a closed system can exchange energy (as heat or work) but not matter, with its surroundings. An isolated system cannot exchange any heat, work, or matter with the surroundings, while an open system can exchange energy and matter. (This scheme of definition of terms is not uniformly used, though it is convenient for some purposes. In particular, some writers use 'closed system' where 'isolated system' is here used.) For a simple system, with only one type of particle (atom or molecule), a closed system amounts to a constant number of particles. However, for systems which are undergoing a chemical reaction, there may be all sorts of molecules being generated and destroyed by the reaction process. In this case, the fact that the system is closed is expressed by stating that the total number of each elemental atom is conserved, no matter what kind of molecule it may be a part of. Mathematically:
William Sanford "Bill" Nye (born November 27, 1955), popularly known as Bill Nye the Science Guy, is an American science educator, comedian, television presenter, actor, writer, scientist, and former mechanical engineer, best known as the host of the Disney/PBS children's science show Bill Nye the Science Guy (1993–1998) and for his many subsequent appearances in popular media as a science educator.
Nye was born on November 27, 1955, in Washington, D.C., to Jacqueline (née Jenkins; 1921–2000), a codebreaker during World War II, and Edwin Darby "Ned" Nye (1917–1997), also a World War II veteran, whose experience without electricity in a Japanese prisoner-of-war camp led him to become a sundial enthusiast. His maternal grandmother was French, from Dancevoir.
After attending Lafayette Elementary and Alice Deal Junior High in the city, he was accepted to the private Sidwell Friends School on a partial scholarship and graduated in 1973. He studied mechanical engineering at Cornell University (where he took an astronomy class taught by Carl Sagan) and graduated with a B.S. in mechanical engineering in 1977. Nye occasionally returns to Cornell as a guest-lecturer of introductory-level astronomy and human ecology classes.