A moment (''momentum'') is a

medieval In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the Post-classical, post-classical period of World history (field), global history. It began with t ...

unit of time A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI) and by extension most of the Western world, is the second, defined as a ...

. The movement of a shadow on a

sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat ...

covered 40 moments in a solar hour, a twelfth of the period between

sunrise Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects. Terminology Al ...

and

sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spring ...

. The length of a solar hour depended on the length of the day, which, in turn, varied with the

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and pol ...

. Although the length of a moment in modern

second The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...

s was therefore not fixed, on average, a moment corresponded to 90 seconds. A solar day can be divided into 24 hours of either equal or unequal lengths, the former being called natural or equinoctial, and the latter artificial. The hour was divided into 4 ''puncti'' (quarter-hours), 10 ''minuta'', or 40 ''momenta''. The unit was used by medieval computists before the introduction of the

mechanical clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...

and the

base 60 Sexagesimal, also known as base 60 or sexagenary, is a numeral system with sixty as its base. It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified form� ...

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 A call to prayer is a summons for participants of a faith to attend a group worship or to begin a required set of prayers. The call is one of the earliest forms of telecommunication, communicating to people across great distances. All religions ...

at intervals throughout the day. The earliest reference found to the moment is from the 8th century writings of the

Venerable Bede Bede ( ; ang, Bǣda , ; 672/326 May 735), also known as Saint Bede, The Venerable Bede, and Bede the Venerable ( la, Beda Venerabilis), was an English monk at the monastery of St Peter and its companion monastery of St Paul in the Kingdom o ...

, who describes the system as 1 solar hour = 4 puncti = 5 lunar puncti = 10 minuta = 15 partes = 40 momenta. Bede was referenced five centuries later by both

Bartholomeus Anglicus Bartholomaeus Anglicus (before 1203–1272), also known as Bartholomew the Englishman and Berthelet, was an early 13th-century Scholastic of Paris, a member of the Franciscan order. He was the author of the compendium ''De proprietatibus rerum' ...

in his early encyclopedia ''De Proprietatibus Rerum'' (On the Properties of Things), as well as

Roger Bacon Roger Bacon (; la, Rogerus or ', also '' Rogerus''; ), also known by the scholastic accolade ''Doctor Mirabilis'', was a medieval English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through empiri ...

, Note the distinction between ''minucia'' and ''minuta'', as well as the introduction of the ''ostenta'', the precursor to the modern minute. by which time the moment was further subdivided into 12 ''ounces'' of 47 ''

atoms Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, an ...

'' each, although no such divisions could ever have been used in observation with equipment in use at the time.

References

Units of time {{time-stub zh:时刻