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 rhetorician would deceive his neighbours,
The sentimentalist himself; while art
Is but a vision of reality.
What portion in the world can the artist have
Who has awakened from the common dream
But dissipation and despair?”
—William Butler Yeats (1865–1939)
“Child of Light! thy limbs are burning
Through the vest which seems to hide them;
As the radiant lines of morning
Through the clouds ere they divide them;
And this atmosphere divinest
Shrouds thee wheresoe’er thou shinest.”
—Percy Bysshe Shelley (1792–1822)
“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)
“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)
“There are no little events in life, those we think of no consequence may be full of fate, and it is at our own risk if we neglect the acquaintances and opportunities that seem to be casually offered, and of small importance.”
—Amelia E. Barr (1831–1919)