World Lines As A Tool To Describe Events
A one-dimensional line or curve can be represented by the coordinates as a function of one parameter. Each value of the parameter corresponds to a point in spacetime and varying the parameter traces out a line. So in mathematical terms a curve is defined by four coordinate functions (where usually denotes the time coordinate) depending on one parameter . A coordinate grid in spacetime is the set of curves one obtains if three out of four coordinate functions are set to a constant.
Sometimes, the term world line is loosely used for any curve in spacetime. This terminology causes confusions. More properly, a world line is a curve in spacetime which traces out the (time) history of a particle, observer or small object. One usually takes the proper time of an object or an observer as the curve parameter along the world line.
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Famous quotes containing the words world, lines, tool, describe and/or events:
“Books, gentlemen, are a species of men, and introduced to them you circulate in the “very best society” that this world can furnish, without the intolerable infliction of “dressing” to go into it. In your shabbiest coat and cosiest slippers you may socially chat even with the fastidious Earl of Chesterfield, and lounging under a tree enjoy the divinest intimacy with my late lord of Verulam.”
—Herman Melville (1819–1891)
“I am so tired of taking to others
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—Lorraine Bethel, African American lesbian feminist poet. “What Chou Mean We, White Girl?” Lines 49-54 (1979)
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—Henry David Thoreau (1817–1862)
“Cruelty is a mystery, and the waste of pain. But if we describe a word to compass these things, a world that is a long, brute game, then we bump against another mystery: the inrush of power and delight, the canary that sings on the skull.”
—Annie Dillard (b. 1945)
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—Ralph Waldo Emerson (1803–1882)