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:
“This world crisis came about without women having anything to do with it. If the women of the world had not been excluded from world affairs, things today might have been different.”
—Alice Paul (1885–1977)
“I struck the board, and cried, “No more.
I will abroad.”
What? Shall I ever sigh and pine?
My lines and life are free; free as the road,
Loose as the wind, as large as store.
Shall I be still in suit?”
—George Herbert (1593–1633)
“One of the great reasons for the popularity of strikes is that they give the suppressed self a sense of power. For once the human tool knows itself a man, able to stand up and speak a word or strike a blow.”
—Charles Horton Cooley (1864–1929)
“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)
“This is certainly not the place for a discourse about what festivals are for. Discussions on this theme were plentiful during that phase of preparation and on the whole were fruitless. My experience is that discussion is fruitless. What sets forth and demonstrates is the sight of events in action, is living through these events and understanding them.”
—Doris Lessing (b. 1919)