Lesson 15-The riddle of time Part Two Background Iformation W BT E ENTER
Lesson 15—The Riddle of Time W B T L E Part Two ENTER
Lesson 15-The riddle of time Background Information Contents 工 Development of Clocks 工工 Biological Clock I工 Calendars W BT E BAC
Lesson 15—The Riddle of Time W B T L E I. Development of Clocks II. Biological Clock III. Calendars Background Information
Lesson 15-The riddle of time . Development of Clocks--Sun Clocks Egyptian shadow clock Obelisk W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E To be continued on the next page. I. Development of Clocks—Sun Clocks
Lesson 15-The riddle of time .evelopment of Clocks--Sun Clocks Not until somewhat recently(that is, in terms of human history) did people find a need for knowing the time of day. As best we know, 5,000 to 6,000 years ago great civilizations in the Middle east and north Africa began to make clocks to augment their calendars. With their attendant bureaucracies, formal religions, and other burgeoning societal activities, these cultures apparently found a need to organize their time more efficiently. W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E Not until somewhat recently (that is, in terms of human history) did people find a need for knowing the time of day. As best we know, 5,000 to 6,000 years ago great civilizations in the Middle East and North Africa began to make clocks to augment their calendars. With their attendant bureaucracies, formal religions, and other burgeoning societal activities, these cultures apparently found a need to organize their time more efficiently. I. Development of Clocks—Sun Clocks To be continued on the next page
Lesson 15-The riddle of time . Development of Clocks--Sun Clocks x The Sumerian culture was lost without passing on its knowledge, but the Egyptians were apparently the next to formally divide their day into parts something like our hours. Obelisks(slender, tapering, four-sided monuments) were built as early as 3500 BC. Their moving shadows formed a kind of sundial, enabling people to partition the day into morning and afternoon. Obelisks also showed the years longest and shortest days when the shadow at noon was the shortest or longest of the year. Later, additional markers around the base of the monument would indicate further subdivisions of time W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E The Sumerian culture was lost without passing on its knowledge, but the Egyptians were apparently the next to formally divide their day into parts something like our hours. Obelisks (slender, tapering, four-sided monuments) were built as early as 3500 BC. Their moving shadows formed a kind of sundial, enabling people to partition the day into morning and afternoon. Obelisks also showed the year’s longest and shortest days when the shadow at noon was the shortest or longest of the year. Later, additional markers around the base of the monument would indicate further subdivisions of time. To be continued on the next page. I. Development of Clocks—Sun Clocks
Lesson 15-The riddle of time .evelopment of Clocks--Sun Clocks Another Egyptian shadow clock or sundial, possibly the first portable timepiece, came into use around 1500 BC. This device divided a sunlit day into 10 parts plus two"twilight hours"in the omit morning and evening. When the long stem with 5 variably spaced marks was oriented east and west in the morning, an elevated crossbar on the east end cast a moving shadow over the marks At noon the device was turned in the opposllo direction to measure the afternoon hours W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E Another Egyptian shadow clock or sundial, possibly the first portable timepiece, came into use around 1500 BC. This device divided a sunlit day into 10 parts plus two “twilight hours” in the morning and evening. When the long stem with 5 variably spaced marks was oriented east and west in the morning, an elevated crossbar on the east end cast a moving shadow over the marks. At noon, the device was turned in the opposite direction to measure the afternoon “hours”. To be continued on the next page. I. Development of Clocks—Sun Clocks
Lesson 15-The riddle of time .evelopment of Clocks-Water Clocks Early water clock W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E To be continued on the next page. I. Development of Clocks—Water Clocks
Lesson 15-The riddle of time .evelopment of Clocks-Water Clocks Su Sung water clock tower W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E To be continued on the next page. I. Development of Clocks—Water Clocks
Lesson 15-The riddle of time .evelopment of Clocks-Water Clocks x Water clocks were among the earliest timekeepers that didn't depend on the observation of celestial bodies. One of the oldest was found in the tomb of the Egyptian pharaoh Amenhotep I, buried around 1500 BC. Later named clepsydras c water thieves") by the greeks, who began using them about 325 BC, these were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. other clepsydras were cylindrical or bowl-shaped containers designed to slowly fill with water coming in at a constant rate W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E Water clocks were among the earliest timekeepers that didn’t depend on the observation of celestial bodies. One of the oldest was found in the tomb of the Egyptian pharaoh Amenhotep I, buried around 1500 BC. Later named clepsydras (“water thieves”) by the Greeks, who began using them about 325 BC, these were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. Other clepsydras were cylindrical or bowl-shaped containers designed to slowly fill with water coming in at a constant rate. To be continued on the next page. I. Development of Clocks—Water Clocks
Lesson 15-The riddle of time .evelopment of Clocks-Water Clocks Markings on the inside surfaces measured the passage of hours"as the water level reached them. These clocks were used to determine hours at night but may have been used in daylight as well. Another version consisted of a metal bowl with a hole in the bottom when placed in a container of water the bowl would fill and sink in a certain time. these were still n use in North Africa in the 20th century. W BT E To be continued on the next page
Lesson 15—The Riddle of Time W B T L E Markings on the inside surfaces measured the passage of “hours” as the water level reached them. These clocks were used to determine hours at night, but may have been used in daylight as well. Another version consisted of a metal bowl with a hole in the bottom; when placed in a container of water the bowl would fill and sink in a certain time. These were still in use in North Africa in the 20th century. To be continued on the next page. I. Development of Clocks—Water Clocks