Chronometry: Timekeeping and the Sun
Olivia Lanni (University of Zurich)
On Dials
Ancient societies used solar observations to subdivide the day and schedule events. Archaeologists have confirmed that Egyptian and Babylonian astronomers developed “shadow clocks,” an early form of sundial, as early as 1500 BCE. Sundials work by manipulating the shadow cast by direct sunlight. Most sundials share a similar design, featuring a central stick called a “gnomon” or “style,” from which the shadow is thrown onto a plane. Through the use of lines radiating away from the center, the observer can tell the time of day.
The Art of Dyalling
Dials vary in complexity, with the simplest generally referred to as “scratch dials” or “incised dials.” More complex dials, such as those used in astronomy and related fields, are grouped together under the term “scientific dials.” The use of scientific dials eventually became so advanced that the English astronomer and mathematician, John Blagrave, wrote a book called The Art of Dyalling in Two Parts (1609), giving detailed instructions on the construction and use of scientific dials.
Despite the differences between simple and complex dials, all enable the viewer to learn more about their natural environment for the purpose of measuring, navigating, or timekeeping.
Whereas astronomers used dials for intricate calculations, ordinary men and women made do with the simple sundials, many of which are still visible on the walls of churches, schools, and other communal buildings.
Another feature common to sundials is their artistry. Sundials often include mottos or paintings inspired by religious texts, mythology, local folklore, or simply the artist’s mood.
Before European mechanical clocks gained in popularity during the thirteenth and fourteenth centuries, sundials were the most common instrument for timekeeping. Whereas other time-measuring devices such as candles or water clocks (which worked by draining water from vessels over a period of time) had existed since antiquity, these devices could only measure time in predetermined intervals, making sundials the only contemporary instrument that captured time as a result of direct planetary movements.
The width of each section on the sundial’s plane even reflected the varying length of the days according to different seasons and hemispheres.
And yet, chronometrical precision was compromised by various factors such as the weather, and the design of the sundial itself. Even within the same location, sundials could be offset or give different readings. With this in mind, we should remember that punctuality is a modern invention.
An Anglo-Saxon Schedule
Though little is known about the historical routines associated with sundials, it is generally accepted that Anglo-Saxon communities divided their days into eight sections, including the night.
The following schedule shows all eight sections with their respective titles, which are rooted in both Old English and Old Norse.
Schedule and Etymology
- Morgan, from 4 1/2 a.m. to 7 1/2 a.m.
- Dæg-mæl, from 7 1/2 to 10 1/2 a.m. (the first tide of the day).
- Mid-dæg, from 10 1/2 a.m. to 1 1/2 p.m.
- Ofanverthr dagr, from 1 1/2 to 4 1/2 p.m. (the last tide of the day).
- Mid-aften, from 4 1/2 to 7 1/2 p.m.
- Ondverth nott, from 7 1/2 to 10 1/2 p.m.
- Mid-niht, from 10 1/2 p.m. to 1 1/2 a.m.
- Ofanverth nott, from 1 1/2 to 4 1/2 a.m
Morgan: Morning German ‘Morgan’
Dæg-mæl: Day-break Marks the beginning of the day on the sundial
Mid-dæg: Mid-day German ‘Mittag’
Ofanverthr dagr: Towards the end of day Old Norse ‘ofan-verðr’ “towards the end”
Mid-aften: Middle of the evening
Ondverth nott: Beginning of the night Old Norse ‘ǫnd-verðr’ “In the beginning of”
Mid-niht: Mid-night
Ofanverth nott: Towards the end of the night
Tide: Time interval on the dial