For thousands of years, devices have been used to measure and keep track of time. The current sexagesimal system of time measurement dates to approximately 2000 BC. The earliest devices relied on shadows cast by the sun, and hence were not useful in cloudy weather or at night and required recalibration as the seasons changed, so they had to invent a clock! Here we summarize the 10 most memorable early firsts in making of clocks.
10. Sundials and Obelisks
Sundials have their origin in shadow clocks , which were the first devices used for measuring the parts of a day.The oldest known shadow clock is from Egypt, and was made from green schist Ancient Egyptian obelisks , constructed about 3500 BC, are also among the earliest shadow clocks. Egyptian shadow clocks divided daytime into 10 parts, with an additional four “twilight hours”—two in the morning, and two in the evening. One type of shadow clock consisted of a long stem with five variable marks and an elevated crossbar which cast a shadow over those marks. It was positioned eastward in the morning, and was turned west at noon. Obelisks functioned in much the same manner: the shadow cast on the markers around it allowed the Egyptians to calculate the time. The obelisk also indicated whether it was morning or afternoon, as well as the summer and winter solstices.
An hourglass ( sandglass , sand timer , sand clock , egg timer ) measures the passage of a few minutes or an hour of time. It has two connected vertical glass bulbs allowing a regulated trickle of material from the top to the bottom. Once the top bulb is empty, it can be inverted to begin timing again. The name hourglass comes from historically common hour timing. Factors affecting the time measured include the amount of sand, the bulb size, the neck width, and the sand quality. Alternatives to sand are powdered eggshell and powdered marble. (Sources disagree on the best material.) Modernly, hourglasses are ornamental or used when an approximate measure suffices, as in egg timers for cooking or for board games. The earliest hourglass appears in the 1338 fresco Allegory of Good Government by Ambrogio Lorenzetti
A water clock or clepsydra is a timepiece in which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel where the amount is then measured. Water clocks, along with sundials, are likely to be the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and the day-counting tally stick. Where and when they were first invented is not known, and given their great antiquity it may never be. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Only a few modern water clocks exist today. In 1979, French scientist Bernard Gitton began creating his Time-Flow Clocks, which are a modern-day approach to the historical version.
7. Candle Clock
A candle clock is a thin candle with consistently spaced markings (usually with numbers), that when burned, indicate the passage of periods of time. While no longer used today, candle clocks provided an effective way to tell time indoors, at night, or on a cloudy day. A candle clock could be easily transformed into a timer by sticking a heavy nail into the candle at the mark indicating the desired interval. When the wax surrounding the nail melts, the nal clatters onto a plate below. It is unknown where and when candle clocks were first used. The earliest reference to their use occurs in a Chinese poem by You Jiangu (520 AD). Here, the graduated candle supplied a means of determining time at night. Similar candles were used in Japan until the early 10th century.
6. Incense Clock
In addition to water, mechanical, and candle clocks, incense clocks were used in the Far East, and were fashioned in several different forms. Incense clocks were first used in China around the 6th century; in Japan, one still exists in the Shōsōin. Several types of incense clock have been found, the most common forms include the incense stick and incense seal. An incense stick clock was an incense stick with calibrations; most were elaborate, sometimes having threads, with weights attached, at even intervals. The weights would drop onto a platter or gong below, signifying that a certain amount of time had elapsed. Some incense clocks were held in elegant trays; open-bottomed trays were also used, to allow the weights to be used together with the decorative tray. Sticks of incense with different scents were also used, so that the hours were marked by a change in fragrance. The incense sticks could be straight or spiraled; the spiraled ones were longer, and were therefore intended for long periods of use, and often hung from the roofs of homes and temples.