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:
“One may say the eternal mystery of the world is its comprehensibility.”
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The signs that stars compose, we need depend
Only on stars that are entirely there
And the apparent space between them. There
Never need be lines between them, puzzling
Our sense of what is what.”
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Made of a heart, and cemented with tears:
Whose parts are as thy hand did frame;
No workman’s tool hath touched the same.”
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“My bad head cannot adjust itself to the way things are.... If I want to depict spring, it has to be in wintertime; if I want to describe a beautiful landscape, I must be enclosed within walls; and I have said a hundred times that if I were put in the Bastille, there I would paint a picture of liberty.”
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“A curious thing about atrocity stories is that they mirror, instead of the events they purport to describe, the extent of the hatred of the people that tell them.
Still, you can’t listen unmoved to tales of misery and murder.”
—John Dos Passos (1896–1970)