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:
“It is not quite the same when we are seventy-two as when we are twenty-seven; still I am glad of what is left, and wish we might both hold out till the victory we have sought is won, but all the same the victory is coming. In the aftertime the world will be the better for it.”
—Lucy Stone (1818–1893)
“He does smile his face into more lines than is in the new map with the augmentation of the Indies.”
—William Shakespeare (1564–1616)
“The first tool I step on
Turned into a weapon.”
—Robert Frost (1874–1963)
“All cruel people describe themselves as paragons of frankness!”
—Tennessee Williams (1914–1983)
“Since events are not metaphors, the literal-minded have a certain advantage in dealing with them.”
—Mason Cooley (b. 1927)