# Time Duration Unit

(Redirected from Time Duration Scale)

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A Time Duration Unit is a unit of measure of a time interval.

**AKA:**Time Scale, Time Metric.**Example(s):****Counter-Example(s):****See:**Physical Space Scale.

## References

### 2009

- (Wikipedia, 2009) ⇒ http://en.wikipedia.org/wiki/Proper_time
- In relativity, proper time is time measured by a single clock between events that occur at the same place as the clock. It depends not only on the events but also on the motion of the clock between the events. An accelerated clock will measure a shorter proper time between two events than a non-accelerated (inertial) clock between the same events. The twins paradox is an example of this. The dark blue vertical line represents an inertial observer measuring a coordinate time interval t between events E1 and E2. The red curve represents a clock measuring proper time τ between the same two events.
- In contrast, coordinate time can be applied to events that occur a distance from an observer. In special relativity, coordinate time is reckoned relative only to inertial observers, whereas proper time can be measured by accelerated observers too.
- 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.
- A Euclidean geometrical analogy is that coordinate time is like distance measured with a straight vertical ruler, whereas proper time is like distance measured with a tape measure. If the tape measure is taut and vertical it measures the same as the ruler, but if the tape measure is not taut, or taut but not vertical, it will not measure the same as the ruler.

### 2009b

- (Bezault, 2009) ⇒ Eric Bezault (2000-2016). http://www.gobosoft.com/eiffel/gobo/time/duration.html
- A duration is an amount of time between two dates, two times or two date/times. Durations can therefore be added to an absolute time and hence get a new absolute time shifted on the oriented time axis by the corresponding amount of time. Although time durations can be compared using a total order relationship, we will see that this is not the case for date durations and date/time durations for which the order relationship is only partial because of the irregularities in the Gregorian calendar