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:
“The world forgetting, by the world forgot.”
—Alexander Pope (1688–1744)
“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 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)
“If you describe things as better than they are, you are considered to be a romantic; if you describe things as worse than they are, you will be called a realist; and if you describe things exactly as they are, you will be thought of as a satirist.”
—Quentin Crisp (b. 1908)
“Nothing that grieves us can be called little: by the eternal laws of proportion a child’s loss of a doll and a king’s loss of a crown are events of the same size.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)