In relativity, proper time is the elapsed time between two events as measured by a clock that passes through both events. The proper time depends not only on the events but also on the motion of the clock between the events. An accelerated clock will measure a smaller elapsed time between two events than that measured by a non-accelerated (inertial) clock between the same two events. The twin paradox is an example of this effect.
In terms of four-dimensional spacetime, proper time is analogous to arc length in three-dimensional (Euclidean) space. By convention, proper time is usually represented by the Greek letter τ (tau) to distinguish it from coordinate time represented by t or T.
By contrast, coordinate time is the time between two events as measured by a distant observer using that observer's own method of assigning a time to an event. In the special case of an inertial observer in special relativity, the time is measured using the observer's clock and the observer's definition of simultaneity.
The concept of proper time was introduced by Hermann Minkowski in 1908, and is a feature of Minkowski diagrams.
Read more about Proper Time: Mathematical Formalism, Examples in General Relativity
Famous quotes containing the words proper and/or time:
“I thought it altogether proper that I should take a brief furlough from official duties at Washington to mingle with you here to-day as a comrade, because every President of the United States must realize that the strength of the Government, its defence in war, the army that is to muster under its banner when our Nation is assailed, is to be found here in the masses of our people.”
—Benjamin Harrison (1833–1901)
“Earth has waited for them,
All the time of their growth
Fretting for their decay:
Now she has them at last!”
—Isaac Rosenberg (1890–1918)