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:
“But the main things about a man are his eyes and his feet. He should be able to see the world and go after it.”
—Alfred Döblin (1878–1957)
“Called as partners in Christ’s service,
Called to ministries of grace,
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Fresh new lines of faith to trace.
May we learn the art of sharing,
Side by side and friend with friend,
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To fulfill God’s chosen end.”
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“The first tool I step on
Turned into a weapon.”
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When your gaze falls
on one of her parts,
like a sick cow fallen
in mud,
it cannot escape.”
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“On the most profitable lie, the course of events presently lays a destructive tax; whilst frankness invites frankness, puts the parties on a convenient footing, and makes their business a friendship.”
—Ralph Waldo Emerson (1803–1882)