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:
“War was return of earth to ugly earth,
War was foundering of sublimities,
Extinction of each happy art and faith
By which the world had still kept head in air.”
—Robert Graves (1895–1985)
“Sweet fire the sire of muse, my soul needs this;
I want the one rapture of an inspiration.
O then if in my lagging lines you miss”
—Gerard Manley Hopkins (1844–1889)
“The veto is a President’s Constitutional right, given to him by the drafters of the Constitution because they wanted it as a check against irresponsible Congressional action. The veto forces Congress to take another look at legislation that has been passed. I think this is a responsible tool for a president of the United States, and I have sought to use it responsibly.”
—Gerald R. Ford (b. 1913)
“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)
“There are many events in the womb of time which will be delivered.”
—William Shakespeare (1564–1616)