Around BC, the Greeks used the idea of a water clock and made their own. The Clepsydras worked by continuously dripping water down a through a narrow opening and accumulating the water in a reservoir where a float carrying a pointer rose and marked the hours.
Another variant of the water clock regulated the flow of water into a bowl and it would eventually sink at a specific time. Plato, the great Greek philosopher, created the first alarm clock. When the water gradually filled up in a jar, it triggered a whistle and woke him up.
The water in Clepsydras was later replaced by mercury as water froze at 0 degrees celcius while Mercury would freeze at negative 38 degrees celcius, making it reliable on cold days. The Ancient Egyptians, once again, improved on their sundial with the merkhet the oldest known astronomical tool. The merkhet uses a string with a weight on the end to accurately measure a straight vertical line. A pair of merkhets were used to establish a North-South line by lining them up with the Pole Star.
This allowed for the measurement of nighttime hours as it measured when certain stars crossed a marked meridian on the sundial. The Ancient Egyptians used the sun to get an idea of the time.
They also constructed large, four-sided pillars that tapered towards the top that would act similarly to sun dials see sundials. These structures were known as Obelisks. Skip to content Loading Search for:. Latest news. Mysterious Megaliths of the Talaiotic People, Menorca. Graham Hancock Website. Ancient Technology. Photo: Science Museum.
Water clocks were among the earliest timekeepers that didn't depend on the observation of celestial bodies. Later named clepsydras "water thieves" by the Greeks, who began using them about BCE, 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.
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. More elaborate and impressive mechanized water clocks were developed between BCE and CE by Greek and Roman horologists and astronomers.
The added complexity was aimed at making the flow more constant by regulating the pressure, and at providing fancier displays of the passage of time. Some water clocks rang bells and gongs; others opened doors and windows to show little figures of people, or moved pointers, dials, and astrological models of the universe.
A Macedonian astronomer, Andronikos, supervised the construction of his Horologion , known today as the Tower of the Winds, in the Athens marketplace in the first half of the first century BCE.
This octagonal structure showed scholars and shoppers both sundials and mechanical hour indicators. It featured a 24 hour mechanized clepsydra and indicators for the eight winds from which the tower got its name, and it displayed the seasons of the year and astrological dates and periods. The Romans also developed mechanized clepsydras, though their complexity accomplished little improvement over simpler methods for determining the passage of time. Third-century Chinese clepsydras drove various mechanisms that illustrated astronomical phenomena.
One of the most elaborate clock towers was built by Su Sung and his associates in CE.
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