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:
“Be it only for a day, it is still a glory without equal to be master of the world just that day.”
—Pierre Corneille (1606–1684)
“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)
“A broken altar, Lord, thy servant rears,
Made of a heart, and cemented with tears:
Whose parts are as thy hand did frame;
No workman’s tool hath touched the same.”
—George Herbert (1593–1633)
“How feeble is all language to describe the horrors we inflict upon these wretches, whom we mason up in the cells of our prisons, and condemn to perpetual solitude in the very heart of our population.”
—Herman Melville (1819–1891)
“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)