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relaxation time
relaxation time
1. The time taken by a disturbed system to reach equilibrium, or the time taken for the magnitude of some parameter to decrease to about 37% of its initial value. For example, the temperature-dependent relaxation time (τ) of a dielectric is related to the relaxation frequency (fr) such that τ = 1/(2πfr). Physically, it is the time taken for an ionic defect to move within a crystal lattice under the influence of an applied alternating electromagnetic field. 2. In geomorphology, the time taken for a system to become adjusted to a sustained change in the nature and/or intensity of external processes. Such an adjustment normally involves a change in the shape of the land-form or landscape constituting the system. Relaxation times vary. The width of a river channel may adjust in response to an increase in discharge in, perhaps, 10 years, while a glaciated mountain range may require 105–106 years to lose the imprint of ice. |
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AILSA ALLABY and MICHAEL ALLABY. "relaxation time." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "relaxation time." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O13-relaxationtime.html AILSA ALLABY and MICHAEL ALLABY. "relaxation time." A Dictionary of Earth Sciences. 1999. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-relaxationtime.html |
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relaxation time
relaxation time The time taken by a geomorphological system to adjust to a sustained change in the nature and/or intensity of an external process, usually by an alteration in the shape of the land-form or landscape. Relaxation times vary. The width of a river channel may increase within 10 years, possibly triggered by a major flood event, in response to an increased discharge; following a climate change, it may be 105–106 years before a glaciated mountain range loses the imprint of ice.
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MICHAEL ALLABY. "relaxation time." A Dictionary of Ecology. 2004. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "relaxation time." A Dictionary of Ecology. 2004. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O14-relaxationtime.html MICHAEL ALLABY. "relaxation time." A Dictionary of Ecology. 2004. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O14-relaxationtime.html |
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relaxation time
relaxation time The time expected for the orbit of a star in a cluster or galaxy to be significantly changed through gravitational perturbation by other stars. For a cluster of N stars this is about 0.1N times the time a typical star takes to cross the cluster (the crossing time). Globular clusters are far older than their relaxation times, and hence are said to be relaxed. For the Galaxy, by contrast, the relaxation time is longer than the age of the Universe.
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Cite this article
"relaxation time." A Dictionary of Astronomy. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "relaxation time." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O80-relaxationtime.html "relaxation time." A Dictionary of Astronomy. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-relaxationtime.html |
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