An hourglass is a mechanical instrument used to measure a specific period of time, determined by the amount of sand contained within it, which will limit the total time to be measured. It consists of two receptacles, generally made of glass, connected to each other, allowing for a regulated flow of material, typically fine sand, from the upper receptacle to the lower one until it is completely transferred. Its operation only requires the potential energy of gravity.
It should be noted that the specific duration of time measured by an hourglass is determined by factors including the quantity and coarseness of the particulate material, the size of the bulbs, and the width of the neck.
HISTORY AND ORIGIN OF THE HOURGLASS
Since the beginning of time, humanity has had the need to measure time. The early Mesopotamian agricultural civilizations created proto-calendars for the purpose of establishing planting and harvesting periods. However, it soon became clear that more precise instruments were needed. That said, the origin of the hourglass is not entirely clear, but it is certain that its predecessor, the clepsydra, or water clock, existed in Babylon and Egypt as early as the 16th century BCE.
As for the origin of hourglasses, there is some uncertainty, but according to one story, in the 8th century, a French monk named Liutprand possibly introduced the first hourglass to Europe. However, the first evidence of the hourglass can be found in Ambrogio Lorenzetti’s fresco “Allegory of Good Government,” dating back to the year 1328 CE.
The earliest known evidence originates from medieval Europe, based on written records found in ship’s logbooks that mentioned hourglasses. One piece of evidence is a sales receipt for an hourglass from Thomas Stetesham, the secretary of the English ship “La George,” in the year 1345. Hourglasses were popular on ships, as they provided the most reliable time measurement at sea, helping sailors determine longitude, distance east or west from a certain point, with reasonable accuracy.
Unlike the clepsydra, the movement of the ship during navigation did not affect the hourglass. Additionally, the use of granular materials in the hourglass, as opposed to liquids, led to more precise measurements, as clepsydras were prone to condensation inside due to temperature fluctuations. Even the Egyptians observed that liquid would evaporate due to changes in climate around 1500 BCE.
The rapid popularity and dissemination of hourglasses were due to their low cost, as they did not require sophisticated technology for manufacturing, and their contents were easy to obtain.
Would you like to continue learning about the history of this object? We will tell you more in our upcoming entries, so stay tuned!