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:
“The popularity of disaster movies ... expresses a collective perception of a world threatened by irresistible and unforeseen forces which nevertheless are thwarted at the last moment. Their thinly veiled symbolic meaning might be translated thus: We are innocent of wrongdoing. We are attacked by unforeseeable forces come to harm us. We are, thus, innocent even of negligence. Though those forces are insuperable, chance will come to our aid and we shall emerge victorious.”
—David Mamet (b. 1947)
“I need not tell you of the inadequacy of the American shipping marine on the Pacific Coast.... For this reason it seems to me that there is no subject to which Congress can better devote its attention in the coming session than the passage of a bill which shall encourage our merchant marine in such a way as to establish American lines directly between New York and the eastern ports and South American ports, and both our Pacific Coast ports and the Orient and the Philippines.”
—William Howard Taft (1857–1930)
“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 describe family values as responsibility towards others, increase of tolerance, compromise, support, flexibility. And essentially the things I call the silent song of life—the continuous process of mutual accommodation without which life is impossible.”
—Salvador Minuchin (20th century)
“When the world was half a thousand years younger all events had much sharper outlines than now. The distance between sadness and joy, between good and bad fortune, seemed to be much greater than for us; every experience had that degree of directness and absoluteness which joy and sadness still have in the mind of a child”
—Johan Huizinga (1872–1945)