Long before any recognisable tools were available to determine distance, parts of the human body such as hands, feet, or arms served to calculate length or height, while the sun, moon and planets measured the passing time. Even today, we still use expressions such as “at arms length” or measure distance in feet, and “hands” is the term used to measure the height of a horse. As civilisation advanced, man developed new tools for calculating every kind of measurement, from the passage of minutes, days and years, to accurate weights and volume.
One of the first tools used for measuring time was a sundial which marked the passage of the sun throughout the day. Numbers were marked out on a large disc on top of which stood a narrow indicator. The shadow cast on each of the numbers indicated the progress of the earth’s rotation, although ancient civilisations believed it marked the sun’s journey through the sky. Time for Time suggests that an early type of sundial was divided into ten parts, with two twilight periods of morning and evening.
A type of water clock, the clepsydra was another early method of measuring time. According to "The Origins of Everyday Things," this instrument dates from the ancient Egyptian period of Amenhotep III and it continued to measure time until the Middle Ages. A small hole was made in the bottom of a container which allowed water to drip through and as the level dropped, it marked the passing time. Although not always accurate, on some of the vessels a moving hand or the sound of a bell indicated the hour.
An hourglass consisted of two identical bulbs of glass connected to each other by a narrowing of the glass to make a thin tube. A measured amount of sand was contained in one bulb and when the glass was turned upside down, the flow of sand between the bulbs marked the passing minutes. In Depth Info suggests that this was be fairly precise as the grains of sand continued to trickle through at a constant rate, regardless of how much sand was left in the bulb.
An astrolabe was an ancient type of astronomical device usually made of brass for measuring the position of the sun or stars. Dating from over two thousand years ago, it was a fairly complicated tool and is sometimes called the first computer. The sky and brightest stars were depicted on the main disc of the astrolabe then moveable components were attached to calculate the passage of each day. The Astrolabe website suggests that in addition to finding specific celestial objects in the sky, the astrolabe was used to record the time of sunrise and sunset, thus determining the length of a day.
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