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:
“Never is a historic deed already completed when it is done but always only when it is handed down to posterity. What we call “history” by no means represents the sum total of all significant deeds.... World history ... only comprises that tiny lighted sector which chanced to be placed in the spotlight by poetic or scholarly depictions.”
—Stefan Zweig (18811942)
“The opera isn’t over till the fat lady sings.”
—Anonymous.
A modern proverb along the lines of “don’t count your chickens before they’re hatched.” This form of words has no precise origin, though both Bartlett’s Familiar Quotations (16th ed., 1992)
“And if thou wilt make me an altar of stone, thou shalt not build it of hewn stone: for if thou lift up thy tool upon it, thou hast polluted it.”
—Bible: Hebrew Exodus 20:25.
“One can describe a landscape in many different words and sentences, but one would not normally cut up a picture of a landscape and rearrange it in different patterns in order to describe it in different ways. Because a photograph is not composed of discrete units strung out in a linear row of meaningful pieces, we do not understand it by looking at one element after another in a set sequence. The photograph is understood in one act of seeing; it is perceived in a gestalt.”
—Joshua Meyrowitz, U.S. educator, media critic. “The Blurring of Public and Private Behaviors,” No Sense of Place: The Impact of Electronic Media on Social Behavior, Oxford University Press (1985)
“As I look at the human story I see two stories. They run parallel and never meet. One is of people who live, as they can or must, the events that arrive; the other is of people who live, as they intend, the events they create.”
—Margaret Anderson (1886–1973)