Moment (unit)

A moment (momentum) is a medieval unit of time. The movement of a shadow on a sundial covered 40 moments in a solar hour, a twelfth of the period between sunrise and sunset. The length of a solar hour depended on the length of the day, which, in turn, varied with the season.^[1] Although the length of a moment in modern seconds was therefore not fixed, on average, a medieval moment corresponded to 90 seconds. A solar day can be divided into 24 hours of either equal or unequal lengths,^[2]^[3] the former being called natural or equinoctial, and the latter artificial. The hour was divided into four puncta (quarter-hours), 10 minuta, or 40 momenta.^[4]

The unit was used by medieval computists before the introduction of the mechanical clock and the base 60 system in the late 13th century. The unit would not have been used in everyday life. For medieval commoners the main marker of the passage of time was the call to prayer at intervals throughout the day.

The earliest reference found to the moment is from the 8th century writings of the Venerable Bede,^[5] who describes the system as 1 solar hour = 4 puncta = 5 lunar puncta^[6]^[7] = 10 minuta = 15 partes = 40 momenta. Bede was referenced five centuries later by both Bartholomeus Anglicus in his early encyclopedia De Proprietatibus Rerum (On the Properties of Things),^[8] as well as Roger Bacon,^[7] by which time the moment was further subdivided into 12 ounces of 47 atoms each, although no such divisions could ever have been used in observation with equipment in use at the time.

References[edit]

^ North, John David (1988). Chaucer's Universe. University of Michigan Press.
^ Bede (1999). The Reckoning of Time. Liverpool University Press. p. 267. ISBN 9780853236931. Retrieved 23 January 2017.
^ Bacon, Roger. Opera quaedam hactenus inedita. Oxford University Press. p. 45. Retrieved 5 July 2014.
^ Bede (1999). The Reckoning of Time. Liverpool University Press. p. 268. ISBN 9780853236931. Retrieved 23 January 2017.
^ Bede (1999). The Reckoning of Time. Liverpool University Press. p. 15. ISBN 9780853236931. Retrieved 23 January 2017.
^ Bede (1999). The Reckoning of Time. Liverpool University Press. p. 73. ISBN 9780853236931. Retrieved 23 January 2017.
^ ^a ^b Bacon, Roger. Opera quaedam hactenus inedita. Oxford University Press. p. 48. Retrieved 5 July 2014. Note the distinction between minucia and minuta, as well as the introduction of the ostenta, the precursor to the modern minute.
^ Middle English dictionary. University of Michigan Press. 1977-12-31. p. 644. ISBN 978-0472011360. Retrieved 5 July 2014.

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[1] North, John David (1988). Chaucer's Universe. University of Michigan Press.

[bede0-2] Bede (1999). The Reckoning of Time. Liverpool University Press. p. 267. ISBN 9780853236931. Retrieved 23 January 2017.

[bacon0-3] Bacon, Roger. Opera quaedam hactenus inedita. Oxford University Press. p. 45. Retrieved 5 July 2014.

[bede1-4] Bede (1999). The Reckoning of Time. Liverpool University Press. p. 268. ISBN 9780853236931. Retrieved 23 January 2017.

[bede2-5] Bede (1999). The Reckoning of Time. Liverpool University Press. p. 15. ISBN 9780853236931. Retrieved 23 January 2017.

[bede3-6] Bede (1999). The Reckoning of Time. Liverpool University Press. p. 73. ISBN 9780853236931. Retrieved 23 January 2017.

[bacon1-7] Bacon, Roger. Opera quaedam hactenus inedita. Oxford University Press. p. 48. Retrieved 5 July 2014. Note the distinction between minucia and minuta, as well as the introduction of the ostenta, the precursor to the modern minute.

[midengdict-8] Middle English dictionary. University of Michigan Press. 1977-12-31. p. 644. ISBN 978-0472011360. Retrieved 5 July 2014.

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v t e Time measurement and standards
Chronometry Orders of magnitude Metrology
International standards	Coordinated Universal Time offset UT ΔT DUT1 International Earth Rotation and Reference Systems Service ISO 31-1 ISO 8601 International Atomic Time 12-hour clock 24-hour clock Barycentric Coordinate Time Barycentric Dynamical Time Civil time Daylight saving time Geocentric Coordinate Time International Date Line IERS Reference Meridian Leap second Solar time Terrestrial Time Time zone 180th meridian
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Time in physics	Absolute space and time Spacetime Chronon Continuous signal Coordinate time Cosmological decade Discrete time and continuous time Proper time Theory of relativity Time dilation Gravitational time dilation Time domain Time-translation symmetry T-symmetry
Horology	Clock Astrarium Atomic clock Complication History of timekeeping devices Hourglass Marine chronometer Marine sandglass Radio clock Watch stopwatch Water clock Sundial Dialing scales Equation of time History of sundials Sundial markup schema
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Archaeology and geology	Chronological dating Geologic time scale International Commission on Stratigraphy
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Other units of time	Instant Flick Shake Jiffy Second Minute Moment Hour Day Week Fortnight Month Year Olympiad Lustrum Decade Century Saeculum Millennium
Related topics	Chronology Duration music Mental chronometry Decimal time Metric time System time Time metrology Time value of money Timekeeper