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.
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.
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