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mass transit

(Encyclopedia)mass transit, public transportation systems designed to move large numbers of passengers. The history of mass transportation is intimately connected to industrialization, urbanization, and the sepa...

transit

(Encyclopedia)transit, in astronomy, passage of a body across a meridian or passage of a small body across the visible disk of a larger one. (The passage of a large body across a smaller one is called an eclipse or...

rapid transit

(Encyclopedia)rapid transit, transportation system designed to allow passenger travel within or throughout an urban area, usually employing surface, elevated, or underground railway systems or some combination of t...

transit compass

(Encyclopedia)transit compass: see surveying.

transit instrument

(Encyclopedia)transit instrument or transit, telescope devised to observe stars as they cross the meridian and used for determining time. Its viewing tube swings on a rigid horizontal axis restricting its movements...

critical mass

(Encyclopedia)critical mass: see chain reaction. ...

atomic mass

(Encyclopedia)atomic mass, the mass of a single atom, usually expressed in atomic mass units (amu). Most of the mass of an atom is concentrated in the protons and neutrons contained in the nucleus. Each proton or n...

mass extinction

(Encyclopedia)mass extinction, the extinction of a large percentage of the earth's species, opening ecological niches for other species to fill. There have been at least ten such events. The five greatest were thos...

mass number

(Encyclopedia)mass number, often represented by the symbol A, the total number of nucleons (neutrons and protons) in the nucleus of an atom. All atoms of a chemical element have the same atomic number (number of pr...

mass production

(Encyclopedia)mass production: see production. ...