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:
“We, too, had good attendance once,
Hearers and hearteners of the work;
Aye, horsemen for companions,
Before the merchant and the clerk
Breathed on the world with timid breath.”
—William Butler Yeats (1865–1939)
“Called as partners in Christ’s service,
Called to ministries of grace,
We respond with deep commitment
Fresh new lines of faith to trace.
May we learn the art of sharing,
Side by side and friend with friend,
Equal partners in our caring
To fulfill God’s chosen end.”
—Jane Parker Huber (b. 1926)
“The first tool I step on
Turned into a weapon.”
—Robert Frost (1874–1963)
“In eloquence, the great triumphs of the art are when the orator is lifted above himself; when consciously he makes himself the mere tongue of the occasion and the hour, and says what cannot but be said. Hence the term abandonment, to describe the self-surrender of the orator.”
—Ralph Waldo Emerson (1803–1882)
“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)