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:
“There’s nothing in the world like the devotion of a married woman. It’s a thing no married man knows anything about.”
—Oscar Wilde (1854–1900)
“I need not tell you of the inadequacy of the American shipping marine on the Pacific Coast.... For this reason it seems to me that there is no subject to which Congress can better devote its attention in the coming session than the passage of a bill which shall encourage our merchant marine in such a way as to establish American lines directly between New York and the eastern ports and South American ports, and both our Pacific Coast ports and the Orient and the Philippines.”
—William Howard Taft (1857–1930)
“The veto is a President’s Constitutional right, given to him by the drafters of the Constitution because they wanted it as a check against irresponsible Congressional action. The veto forces Congress to take another look at legislation that has been passed. I think this is a responsible tool for a president of the United States, and I have sought to use it responsibly.”
—Gerald R. Ford (b. 1913)
“Archaeologists have uncovered six-thousand-year-old clay tablets from southern Babylonia that describe in great detail how the adults of that community found the younger generation to be insolent and disobedient.”
—Lawrence Kutner (20th century)
“One cannot be a good historian of the outward, visible world without giving some thought to the hidden, private life of ordinary people; and on the other hand one cannot be a good historian of this inner life without taking into account outward events where these are relevant. They are two orders of fact which reflect each other, which are always linked and which sometimes provoke each other.”
—Victor Hugo (1802–1885)