Distance Versus Directed Distance and Displacement
Distance cannot be negative and distance travelled never decreases. Distance is a scalar quantity or a magnitude, whereas displacement is a vector quantity with both magnitude and direction.
The distance covered by a vehicle (for example as recorded by an odometer), person, animal, or object along a curved path from a point A to a point B should be distinguished from the straight line distance from A to B. For example whatever the distance covered during a round trip from A to B and back to A, the displacement is zero as start and end points coincide. In general the straight line distance does not equal distance travelled, except for journeys in a straight line.
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Famous quotes containing the words distance and/or directed:
“For time is the longest distance between two places.”
—Tennessee Williams (1914–1983)
“What is clear is that Christianity directed increased attention to childhood. For the first time in history it seemed important to decide what the moral status of children was. In the midst of this sometimes excessive concern, a new sympathy for children was promoted. Sometimes this meant criticizing adults. . . . So far as parents were put on the defensive in this way, the beginning of the Christian era marks a revolution in the child’s status.”
—C. John Sommerville (20th century)