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17 hours ago · Astrodynamics. In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun. The laws modified the heliocentric theory of Nicolaus Copernicus, replacing its circular orbits and epicycles with elliptical trajectories, and explaining how planetary velocities vary.
17 hours ago · Neutrons are required for the stability of nuclei, with the exception of the single-proton hydrogen nucleus. Neutrons are produced copiously in nuclear fission and fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes.
17 hours ago · History Early history. The hypothesis of dark matter has an elaborate history. In the appendices of the book Baltimore lectures on molecular dynamics and the wave theory of light where the main text was based on a series of lectures given in 1884, Lord Kelvin discussed the potential number of stars around the Sun from the observed velocity dispersion of the stars near the Sun, assuming that ...
17 hours ago · Definition [ edit] Metaphysics is the study of the most general features of reality, including existence, objects and their properties, possibility and necessity, space and time, change, causation, and the relation between matter and mind. It is one of the oldest branches of philosophy. [1]
17 hours ago · Source field. In theoretical physics, a source field is a background field coupled to the original field as. . This term appears in the action in Richard Feynman 's path integral formulation and responsible for the theory interactions. In Julian Schwinger 's formulation the source is responsible for creating or destroying (detecting) particles.
17 hours ago · Definitions. A tornado is a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud. [18] For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base.
17 hours ago · Terminology. The term "Zionism" is derived from the word Zion (Hebrew: ציון, romanized: Tzi-yon), a hill in Jerusalem, widely symbolizing the Land of Israel. Throughout eastern Europe in the late 19th century, numerous grassroots groups promoted the national resettlement of the Jews in their homeland, as well as the revitalization and cultivation of the Hebrew language.
