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Pre - 3000 BCE, early people realized that when the sun rose, the light part of the day began, and it ended when the sun set.
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The early Egyptians told time by observing the shadow cast by an obelisk. The shadow helped them determine the position of the sun. Photo credit:https://pre00.deviantart.net/7636/th/pre/i/2008/037/d/5/egypt_obelisk_by_evolution1990.jpg
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Early Egyptians began using water clocks to track time during the evening and on overcast days. One of the earliest water clocks was found in the tomb of Amenhotep I. Bellis, Mary. "The History of Sun Clocks, Water Clocks and Obelisks." ThoughtCo, Apr. 13, 2017, thoughtco.com/history-of-sun-clocks-4078627. Photo credit: https://s-media-cache-ak0.pinimg.com/avatars/pmtimeservice-82_75.jpg
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People in ancient Greece began using water clocks as a way to tell time. Some of these were stone vessels with sloping sides that had a small hole drilled in the bottom, which allowed water to drip out at a steady rate.
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The Babylonians created a sundial, which had a vertical marker attached to the centre. It would cast a shadow on a 12-hour clock face that was written on the dial. The position of the shadow showed the time of day. Photo Credit: https://www.timecenter.com/articles/when-time-began-the-history-and-science-of-sundials/
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The first reference to the use of a candle clock was in a Chinese poem by You Jiangu . The candle was divided into section, and each section required 20 minutes to burn. The entire candle required 4 hours to burn completely.
https://en.wikipedia.org/wiki/Candle_clock
Photo credit: https://upload.wikimedia.org/wikipedia/commons/thumb/2/2f/Kerzenuhr.jpg/330px-Kerzenuhr.jpg -
The hourglass was first used in Europe, allowing people to tell time without the need of sunlight. In the 1300's, they were popular on ships. They were suspended and not affected by the swaying of the ship.
http://plus.google.com/100042186937427165447 -
The first mechanical clocks were built in Europe, and used a mainspring and balance wheel. http://www.time-for-time.com/timeline.htm
Photo credit: https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcT7YVCjQB3K5BOXf6gB_wexKA09zWd-NsSZTvPOBKYrbF7YHsrCtw -
The first portable or wearable watches used coiled springs to move the inner mechanisms. They were used first by people in Italy.
Picture credit: http://gajitz.com/wp-content/uploads/2009/10/first-painting-of-a-watch.jpg -
Pendulum clocks are mechanical clocks that have a swinging pendulum that controls the mechanism inside. They have greater accuracy, and allow the telling of time in seconds, minutes, as well as hours.
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Digital clocks and watches use batteries and a quartz crystal, instead of coils and springs. They usually display the time with a number.
http://blog.onlineclock.net/history-of-digital-clocks-watches/
Photo credit: http://blog.onlineclock.net/wp-content/uploads/2010/09/hamilton-pulsar-watch.jpg
