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Moment (unit)

physical science Maturity 11-13 Next article →

A moment is a medieval unit of time used before modern clocks.

CLM 14456 71r detail
CLM 14456 71r detail

It served as a way to measure small intervals within a solar hour. A solar hour is a twelfth of the period between sunrise and sunset. Unlike our modern minutes, the length of a moment was not fixed. It changed based on the length of the day and the season. On average, a medieval moment lasted about 90 seconds. This system helped scholars track time before the base 60 system became common.

The mechanism of the moment relied on the movement of the sun.

CLM 14456 71r detail
CLM 14456 71r detail

People watched how a shadow moved across a sundial to track time. This shadow movement covered 40 moments in a single solar hour. Because the sun's position changes with the seasons, the hour changed too. In summer, the solar hour was longer than in winter. Therefore, the moments within those hours also changed in length. This made the moment a flexible unit tied to the natural world.

There were several ways to divide time during the Middle Ages.

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CLM 14456 71r detail

A solar day could be split into 24 hours. These hours were either natural or artificial. Natural or equinoctial hours were of equal lengths. Artificial hours were of unequal lengths. Within these hours, the moment could be divided differently. A single solar hour could be split into 4, 10, or 40 moments. This variety allowed different systems of measurement to exist.

We learn about these time divisions through historical writings.

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CLM 14456 71r detail

The earliest reference comes from the 8th century. The Venerable Bede described the system in his writings. He noted that one solar hour could be 4, 5, 10, 15, or 40 moments. Five centuries later, other scholars referenced his work. Bartholomeus Anglicus included these ideas in his encyclopedia, *On the Properties of Things*. Roger Bacon also wrote about these measurements in his own work.

As time measurement became more complex, scholars created smaller units.

CLM 14456 71r detail
CLM 14456 71r detail

They introduced the ounce, which was a precursor to the modern minute. Some thinkers even subdivided the moment into much smaller parts. They divided a moment into 12 ounces. Each of these ounces was made of 47 atoms. These atoms were tiny, theoretical parts of a moment. No one could actually observe these atoms with the equipment available at the time.

Most common people did not use moments in their daily lives.

CLM 14456 71r detail
CLM 14456 71r detail

Instead, they relied on more natural or social markers. They watched the passage of the sun to see the time. They also used calls to prayer at various intervals to mark the day. The moment was a tool for computists, who were people who calculated time. It was not a unit used for everyday tasks by the general public.

The era of the moment ended in the late 13th century.

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CLM 14456 71r detail

This change happened because of two major developments. First, the mechanical clock was introduced. Second, the base 60 system began to be used for time. These new technologies provided a fixed way to measure time. This replaced the seasonal and flexible system of the medieval moment. Today, our time is constant rather than changing with the sun.

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