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:
“We can speak very much to the purpose and yet in such a way that the whole world cries out in contradiction: namely, when we are not speaking to the whole world.”
—Friedrich Nietzsche (1844–1900)
“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 first tool I step on
Turned into a weapon.”
—Robert Frost (1874–1963)
“The moment when she crawled out onto the back of the open limousine in which her husband had been murdered was the first and last time the American people would see Jacqueline Bouvier Kennedy Onassis crawl.... She was the last great private public figure in this country. In a time of gilt and glitz and perpetual revelation, she was perpetually associated with that thing so difficult to describe yet so simple to recognize, the apotheosis of dignity.”
—Anna Quindlen (b. 1952)
“There are events which are so great that if a writer has participated in them his obligation is to write truly rather than assume the presumption of altering them with invention.”
—Ernest Hemingway (1899–1961)