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:
“Signal smokes, war drums, feathered bonnets against the western sky. New messiahs, young leaders are ready to hurl the finest light cavalry in the world against Fort Stark. In the Kiowa village, the beat of drums echoes in the pulsebeat of the young braves. Fighters under a common banner, old quarrels forgotten, Comanche rides with Arapaho, Apache with Cheyenne. All chant of war. War to drive the white man forever from the red man’s hunting ground.”
—Frank S. Nugent (1908–1965)
“Your letter is come; it came indeed twelve lines ago, but I
could not stop to acknowledge it before, & I am glad it did not
arrive till I had completed my first sentence, because the
sentence had been made since yesterday, & I think forms a very
good beginning.”
—Jane Austen (1775–1817)
“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)
“I don’t try to describe the future. I try to prevent it.”
—Ray Bradbury (b. 1920)
“If I have renounced the search of truth, if I have come into the port of some pretending dogmatism, some new church, some Schelling or Cousin, I have died to all use of these new events that are born out of prolific time into multitude of life every hour. I am as bankrupt to whom brilliant opportunities offer in vain. He has just foreclosed his freedom, tied his hands, locked himself up and given the key to another to keep.”
—Ralph Waldo Emerson (1803–1882)