periods per second
81pulsar — /pul sahr/, n. Astron. one of several hundred known celestial objects, generally believed to be rapidly rotating neutron stars, that emit pulses of radiation, esp. radio waves, with a high degree of regularity. [1965 70; puls(ating st)ar, on the… …
82space exploration — Investigation of the universe beyond Earth s atmosphere by means of manned and unmanned spacecraft. Study of the use of rockets for spaceflight began early in the 20th century. Germany s research on rocket propulsion in the 1930s led to… …
83Onychophora — Temporal range: 40–0 Ma …
84Colonization of the Moon — Lunar outpost redirects here. For NASA s plan to construct an outpost between 2012 and 2024, see Lunar outpost (NASA). Moonbase redirects here. For other uses, see Moonbase (disambiguation). 1986 artist concept The colonization of the Moon is the …
85cell — cell1 cell like, adj. /sel/, n. 1. a small room, as in a convent or prison. 2. any of various small compartments or bounded areas forming part of a whole. 3. a small group acting as a unit within a larger organization: a local cell of the… …
86nuclear fusion — fusion (def. 4). [1895 1900] * * * Process by which nuclear reactions between light elements form heavier ones, releasing huge amounts of energy. In 1939 Hans Bethe suggested that the energy output of the sun and other stars is a result of fusion …
87musical sound — Introduction any tone with characteristics such as controlled pitch and timbre. The sounds are produced by instruments in which the periodic vibrations can be controlled by the performer. That some sounds are intrinsically musical,… …
88Mount Meager — The Mount Meager volcanic complex rising above the Pemberton Valley. Summits left to right are Capricorn Mountain, Mount Meager proper and Plinth Peak …
89Parkinson's disease — Parkinson s redirects here. For other uses, see Parkinson s (disambiguation). Parkinson s disease Classification and external resources …
90valley — valleylike, adj. /val ee/, n., pl. valleys. 1. an elongated depression between uplands, hills, or mountains, esp. one following the course of a stream. 2. an extensive, more or less flat, and relatively low region drained by a great river system …
