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| Two circular diagrams showing the division of the day and of the week, from a Carolingian manuscript (Clm 14456 fol. 71r) of St. Emmeram Abbey. The day is divided into 24 hours, and each hour into 4 puncta, 10 minuta and 40 momenta. Similarly, the week is divided into seven days, and each day into 96 puncta, 240 minuta and 960 momenta. |
A moment (momentum) was a medieval unit of
time. The movement of a shadow on a sundial covered 40 moments in a solar hour. An hour in this case means one twelfth of
the period between sunrise and sunset (see planetary hours).
The length of a
solar hour depended on the length of the day, which in turn varied with the
season, so the length of a moment in modern seconds was not fixed, but on
average, a moment corresponds to 90 seconds:
A day was divided into 24 hours(of unequal lengths, twelve hours of the day and the night each), and an hour
was divided into four puncta
(quarter-hours), ten minuta and 40 momenta. 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 our medieval counterparts the main marker of the passage of
time was the call to prayer at intervals throughout the day. The earliest
reference we have to the moment is from the 8th century writings of the
Venerable Bede. Bede describes the system as 1 hour = 4 points = 10 minutes =
15 parts = 40 moments. Bede was referenced four centuries later by Bartholomeus Anglicus in his early encyclopedia De
Proprietatibus Rerum (On the Properties of Things). Centuries after Bede's
description, the moment was further divided into 60 ostents, although no such
divisions could ever have been used in observation with equipment in use at the
time.
