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:
“Life is crazy. Now, maybe you knew this all along. But before I had children, I actually held on to the illusion that there was some sense of order to the universe.... I am now convinced that we are all living in a Chagall painting—a world where brides and grooms and cows and chickens and angels and sneakers are all mixed up together, sometimes floating in the air, sometimes upside down and everywhere.”
—Susan Lapinski (20th century)
“Was seiz’d by the spirit that trails in the lines underfoot,
The rim, the sediment that stands for all the water and all the land
of the globe.
Fascinated, my eyes reverting from the south, dropt, to follow those slender windrows,
Chaff, straw, splinters of wood, weeds, and the sea-gluten,
Scum, scales from shining rocks, leaves of salt-lettuce, left by the tide,”
—Walt Whitman (1819–1892)
“Is it not possible that an individual may be right and a government wrong? Are laws to be enforced simply because they were made? or declared by any number of men to be good, if they are not good? Is there any necessity for a man’s being a tool to perform a deed of which his better nature disapproves?”
—Henry David Thoreau (1817–1862)
“all the categories which we employ to describe conscious mental acts, such as ideas, purposes, resolutions, and so on, can be applied to ... these latent states.”
—Sigmund Freud (1856–1939)
“The phenomenon of nature is more splendid than the daily events of nature, certainly, so then the twentieth century is splendid.”
—Gertrude Stein (1874–1946)