# proper time

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## proper time

Time measured by a clock that is sharing the observer's motion. Clocks moving with respect to the observer, or experiencing a different gravitational field, will measure time to flow at a different rate to that of proper time. See also relativity, special theory.

## Proper Time

in the theory of relativity, the time measured by a clock in the proper frame of reference of a moving body. In other words, proper time is the time measured by a clock rigidly attached to the body—that is, a clock at rest with respect to the body and located in the same place as the body.

The duration of a process, as measured by an observer outside the body in which the process occurs, depends on the relative velocity of the observer and the body. In measurements far from attracting bodies, the special theory of relativity can be used (seeRELATIVITY, THEORY OF). Suppose the measurements are made in some inertial (laboratory) frame of reference and the body moves with the constant velocity v relative to the frame. The relation between the proper time interval Δτ and the observer’s time interval Δτ is then , where c is the speed of light in a vacuum. If v varies with time, then the proper time interval corresponding to the observer’s time interval between t1 and t2 is

When gravitational fields are present, the general theory of relativity must be used. The strength of a gravitational field is indicated by the absolute value of the gravitational potential φ. The potential is in fact negative; outside the field, φ is assumed to be equal to zero. The larger the absolute value of φ, the slower the flow of the proper time of a process in the gravitational field from the point of view of an observer outside the field. For fields that are sufficiently weak—that is, when ǀφǀ/c2 << 1—the relation between the proper time interval Δτ according to a stationary clock at a point with the potential φ and the time interval Δt for a stationary observer outside the field is given by the equation Δτ = (1 – ǀφǀ/c2t.

It can be seen from the above equations that the proper time interval is always shorter than the time interval measured in any other frame of reference.

I. IU. KOBZAREV

## proper time

[′präp·ər ′tīm]
(relativity)
The time measured by an ideal clock that is carried along with a specified particle, and is based on the invariant timelike space-time intervals between points along the particle's trajectory.
References in classic literature ?
'The proper time, sir!' retorted his father, 'the proper time's no time.'
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You'll hear all about Jonas in the proper time and place.
No, D'Artagnan considered that things are never well done when they are not reserved to their proper time. He was hungry; he supped, he went to bed.
Although I don't despise sweet things in proper time and place, I found the supper rather light."
We will produce him at the proper time. Did you carry anything there with you."
There are some men to whom getting up at the proper time is an utter impossibility.
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Again is this a proper time for Oli to visit London?
Meanwhile, Justice Ejaz Afzal assured the PML-N leader that he will get proper time for his defence.
Through what GatesAir says is an "exclusive algorithm," the devices canensure proper time alignment between analog and digital (HD Radio) signals by removing the objectionable blending artifacts.

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