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Times in the geological past when great glaciers extended far into Europe, Asia and America.
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the angle between the orbital plane of a satellite or planet and some reference plane, usually linked to the center of attraction (e.g. Earth equatorial plane, or plane of the ecliptic). The angle between two planes is defined as the angle between their perpendiculars, at any point of their intersection. Orbital inclination is one of 6 orbital elements.
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The property of matter to resists accleration or deceleration, i.e. any motion which is not in a straight line and with constant velocity
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an instrument for comparing masses using only their inertia, and not relying on gravity. Examples are the instrument used for monitoring astronaut mass aboard space station "Skylab" and the sawblade device described in "Stargazers."
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A force which must be added to the equations of motion when Newton's laws are used in a rotating or otherwise accelerating frame of reference. Some call it a "fictional force" because when the same motion is solved in the frame of the "outside world&," these forces do not appear.
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(or infra-red light). The region of the electromagnetic spectrum adjacent to that of visible light, but with longer wavelengths (0.65-10 micrometers, typical). Infra-red radiation is emitted by hot objects and by excited molecules. See also greenhouse effect.
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usually, an atom from which one or more electrons have been torn off, leaving a positively charged particle. "Negative ions" are atoms which have acquired one or more extra electrons, and clusters of atoms can also become ions.
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the process by which a neutral atom, or a cluster of such atoms, becomes an ion. This may occur, for instance, by absorbtion of light ("photoionization") or by a collision with a fast particle ("impact ionization"). Also, certain molecules (such as table salt or sodium chloride, NaCl) are formed by natural ions (like Na+ and Cl-) held together by their electric attraction, and they may fall apart when dissolved in water (which weakens the attraction), enabling the solution to conduct electricity.
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The repetition of a process of calculation again and again, each time improving the accuracy of the result.
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