History of timekeeping devices

context: en: Although the Greeks and Romans did much to advance water clock technology, they still continued to use shadow clocks. The mathematician and astronomer Theodosius of Bithynia, for example, is said to have invented a universal sundial that was accurate anywhere on Earth, though little is known about it. Others wrote of the sundial in the mathematics and literature of the period. Marcus Vitruvius Pollio, the Roman author of De Architectura, wrote on the mathematics of gnomons, or sundial blades. During the reign of Emperor Augustus, the Romans constructed the largest sundial ever built, the Solarium Augusti. Its gnomon was an obelisk from Heliopolis. Similarly, the obelisk from Campus Martius was used as the gnomon for Augustus's zodiacal sundial. Pliny the Elder records that the first sundial in Rome arrived in 264 BC, looted from Catania, Sicily; according to him, it gave the incorrect time until the markings and angle appropriate for Rome's latitude were used—a century later.
qas: question: zh_tw: 比提尼亞的狄奧多以什麼而聞名？
answers: en: text: mathematician and astronomer

context: en: Egyptian shadow clocks divided daytime into 12 parts with each part further divided into more precise parts. 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 so that the rising sun cast a shadow over the marks, and was turned west at noon to catch the afternoon shadows. 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. A third shadow clock, developed c. 1500 BC, was similar in shape to a bent T-square. It measured the passage of time by the shadow cast by its crossbar on a non-linear rule. The T was oriented eastward in the mornings, and turned around at noon, so that it could cast its shadow in the opposite direction.Although accurate, shadow clocks relied on the sun, and so were useless at night and in cloudy weather. The Egyptians therefore developed a number of alternative timekeeping instruments, including water clocks, and a system for tracking star movements. The oldest description of a water clock is from the tomb inscription of the 16th-century BC Egyptian court official Amenemhet, identifying him as its inventor. There were several types of water clocks, some more elaborate than others. One type consisted of a bowl with small holes in its bottom, which was floated on water and allowed to fill at a near-constant rate; markings on the side of the bowl indicated elapsed time, as the surface of the water reached them. The oldest-known waterclock was found in the tomb of pharaoh Amenhotep I (1525–1504 BC), suggesting that they were first used in ancient Egypt. Another Egyptian method of determining the time during the night was using plumb-lines called merkhets. In use since at least 600 BC, two of these instruments were aligned with Polaris, the north pole star, to create a north–south meridian. The time was accurately measured by observing certain stars as they crossed the line created with the merkhets.
qas: question: zh_tw: 方尖碑有何象徵意義？
answers: en: text: whether it was morning or afternoon

context: en: In Greek tradition, clepsydrae were used in court; later, the Romans adopted this practice, as well. There are several mentions of this in historical records and literature of the era; for example, in Theaetetus, Plato says that "Those men, on the other hand, always speak in haste, for the flowing water urges them on". Another mention occurs in Lucius Apuleius' The Golden Ass: "The Clerk of the Court began bawling again, this time summoning the chief witness for the prosecution to appear. Up stepped an old man, whom I did not know. He was invited to speak for as long as there was water in the clock; this was a hollow globe into which water was poured through a funnel in the neck, and from which it gradually escaped through fine perforations at the base". The clock in Apuleius's account was one of several types of water clock used. Another consisted of a bowl with a hole in its centre, which was floated on water. Time was kept by observing how long the bowl took to fill with water.Although clepsydrae were more useful than sundials—they could be used indoors, during the night, and also when the sky was cloudy—they were not as accurate; the Greeks, therefore, sought a way to improve their water clocks. Although still not as accurate as sundials, Greek water clocks became more accurate around 325 BC, and they were adapted to have a face with an hour hand, making the reading of the clock more precise and convenient. One of the more common problems in most types of clepsydrae was caused by water pressure: when the container holding the water was full, the increased pressure caused the water to flow more rapidly. This problem was addressed by Greek and Roman horologists beginning in 100 BC, and improvements continued to be made in the following centuries. To counteract the increased water flow, the clock's water containers—usually bowls or jugs—were given a conical shape; positioned with the wide end up, a greater amount of water had to flow out in order to drop the same distance as when the water was lower in the cone. Along with this improvement, clocks were constructed more elegantly in this period, with hours marked by gongs, doors opening to miniature figurines, bells, or moving mechanisms. There were some remaining problems, however, which were never solved, such as the effect of temperature. Water flows more slowly when cold, or may even freeze.Between 270 BC and AD 500, Hellenistic (Ctesibius, Hero of Alexandria, Archimedes) and Roman horologists and astronomers began developing more elaborate mechanized water clocks. The added complexity was aimed at regulating the flow and at providing fancier displays of the passage of time. For example, some water clocks rang bells and gongs, while others opened doors and windows to show figurines of people, or moved pointers, and dials. Some even displayed astrological models of the universe.
qas: question: zh_tw: 哪裡使用漏壺？
answers: en: text: in court

question: zh_tw: 增加的壓力會導致什麼結果？
answers: en: text: water to flow more rapidly

context: en: 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, although its characters are not Chinese, but Devanagari. Due to their frequent use of Devanagari characters, suggestive of their use in Buddhist ceremonies, Edward H. Schafer speculated that incense clocks were invented in India. Although similar to the candle clock, incense clocks burned evenly and without a flame; therefore, they were more accurate and safer for indoor use.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. In Japan, a geisha was paid for the number of senkodokei (incense sticks) that had been consumed while she was present, a practice which continued until 1924.Incense seal clocks were used for similar occasions and events as the stick clock; while religious purposes were of primary importance, these clocks were also popular at social gatherings, and were used by Chinese scholars and intellectuals. The seal was a wooden or stone disk with one or more grooves etched in it into which incense was placed. These clocks were common in China, but were produced in fewer numbers in Japan. To signal the passage of a specific amount of time, small pieces of fragrant woods, resins, or different scented incenses could be placed on the incense powder trails. Different powdered incense clocks used different formulations of incense, depending on how the clock was laid out. The length of the trail of incense, directly related to the size of the seal, was the primary factor in determining how long the clock would last; all burned for long periods of time, ranging between 12 hours and a month.While early incense seals were made of wood or stone, the Chinese gradually introduced disks made of metal, most likely beginning during the Song dynasty. This allowed craftsmen to more easily create both large and small seals, as well as design and decorate them more aesthetically. Another advantage was the ability to vary the paths of the grooves, to allow for the changing length of the days in the year. As smaller seals became more readily available, the clocks grew in popularity among the Chinese, and were often given as gifts. Incense seal clocks are often sought by modern-day clock collectors; however, few remain that have not already been purchased or been placed on display at museums or temples.
qas: question: zh_tw: 香鍾為什麼在室內更安全？
answers: en: text: burned evenly and without a flame

context: en: Other ancient timekeeping devices include the candle clock, used in ancient China, ancient Japan, England and Mesopotamia; the timestick, widely used in India and Tibet, as well as some parts of Europe; and the hourglass, which functioned similarly to a water clock.  The sundial, another early clock, relies on shadows to provide a good estimate of the hour on a sunny day.  It is not so useful in cloudy weather or at night and requires recalibration as the seasons change (if the gnomon was not aligned with the Earth's axis).
qas: question: zh_tw: 古代用什麼來確定時間？
answers: en: text: candle clock