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:
“But the old world was restored and we returned
To the dreary field and workshop, and the immemorial feud
Of rich and poor. Our victory was our defeat.”
—Sir Herbert Read (1893–1968)
“We stand in the tumult of a festival.
What festival? This loud, disordered mooch?
These hospitaliers? These brute-like guests?
These musicians dubbing at a tragedy,
A-dub, a-dub, which is made up of this:
That there are no lines to speak? There is no play.”
—Wallace Stevens (1879–1955)
“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)
“Who shall describe the inexpressable tenderness and immortal life of the grim forest, where Nature, though it be midwinter, is ever in her spring, where the moss-grown and decaying trees are not old, but seem to enjoy a perpetual youth.”
—Henry David Thoreau (1817–1862)
“We have defined a story as a narrative of events arranged in their time-sequence. A plot is also a narrative of events, the emphasis falling on causality. “The king died and then the queen died” is a story. “The king died, and then the queen died of grief” is a plot. The time sequence is preserved, but the sense of causality overshadows it.”
—E.M. (Edward Morgan)