What Is A Water Clock And How Does It Work?


A water clock is one of the most ancient clocks that we know of. It was one of our primitive inventions to cope up with the lack of coordination. When humanity was still a bit young we used to mark time by the rising and setting of the sun. And a month by the waxing and waning of the moon. But as we grew we built better and more precise ways of telling time. And, one of our first tries to this was the water clock. If you want to know more about the history of clocks interestingengineering.com has a great article written on just that “ The very long and fascinating history of clocksOpens in a new tab.“, so do give it a look if you are interested. As in this article, we are just going to discuss the water clock in more depth

What Is A Water Clock?

The very first water clock that was used to measure time was back in 5th century B.C. To elaborate, some amount of water was put in a vessel. That was allowed to escape through a hole in the bottom. The time determined varied according to the size of the vessel and the hole made at the bottom

A picture of an ancient water clock to better answer "What is a water clock And how does it work?"
What is a water clock And how does it work?

It was all before we had the liberty of wearing fancy time-telling devices on our wrists. Or even the scientific knowledge to make the atomic clock. Which helps function the internet as well as the GPS system properly. So, how was it possible for anyone to maintain some kind of a schedule. Well, we had sundials that used the shadow made through the sun to showcase what time of the day it was, but this wouldn’t work on cloudy days or even at night as there would be no sun to produce any kind of a shadow. So, Egyptians thought of making a time measurement device using the most common liquid around, water. They were educated enough to know that as the level of water in a container drops, the outflow of the stream coming out of the hole made will also drop

A picture of different flows of water to better answer "What is a water clock And how does it work?"
What is a water clock And how does it work?

History Of Waterclocks

Egyptians started off by using the water clock as more of a timer than a clock. It started off being used in the Egyptian courtrooms where a lawyer would be allowed one bucket of water to let him know of the time he has left whilst presented his case. Moreover, in order to account for interruptions and or breaks, they would simply close the whole with a whole.

An advancement in this way of water clock was seen in the Jarasandh period of Korean history. Engineers of this time took advantage of the buoyancy force,( the upthrust force that the water applies on any object when it is immersed into the water) to develop an alarming system. They already knew through the teachings of Archemdis. That the buoyant/upthrust acting on the body could cause the body to float depending on the density of the object.

So, they build another mechanism, where the runoff water fills the secondary vessel object. An object with a lower density is placed in the second vessel. Which will float and come up as the water is filled in the second container.

A picture of a water clock to better answer "What is a water clock And how does it work?"
What is a water clock And how does it work?

Some further history

This helped the Korean dynasty that used this technique to create an alarm clock that made different sounds for different times of the day. As time went on, this technique came into further use through various different forms. But, there was a problem, time was measured from a starting point. And the container needed to be emptied and refilled constantly. But then came along the solution,”Siphoning”. This is where we use a vacuum that allows external atmospheric pressure to move liquid from a higher placed cup/object to a lower placed cup/object

A picture of siphnoing to better answer "What is a water clock And how does it work?"
What is a water clock And how does it work?

This flow of liquid will continue till either the liquid heights from the ground at equilibrium. Or, the upper cup runs out of fluid. It starts off like shown in the picture below

Another picture of siphoning
What is a water clock And how does it work?

More details on how the water clock works

And then the liquid from the upper cup is pulled from the upper cup to the lower cup due to the atmospheric pressure and gravity. And once surface heights reach equilibrium, forces will be in balance in the siphon. Leading the flow of liquid to stop. With the understanding of this(siphon), Sidious, a greek engineer was eventually able to make this system automatic and self restarting. This was something that the world had never seen before. This ultimately led to the biggest problem of the water clock, which was the constant need to get it refilled, being solved.

But, there was still one problem. This was that at that time, daylight hours were divided into twelve. So, the hours were shorter in winter than whilst in summer. So, to solve this, Sedious added two-hour lines to differ in their locations. And appear near or further apart depending on the time of the year. This solution by Sedious led to the Greeks having the most accurate clock of the time. Moreover, a clock that worked 24/7 without the use of refilling.

Are water clocks still used today?

Nowadays, we have excelled in our technology to a level where no water clock can reach. But, the sinking bowl water clock is still used in some parts of the world today as a timer.

Who used the water clock?

The oldest water clock dates back to 1500 b.c. The Greeks began using them around 325b.c. and dubbed them Clepydras (water thieves).

Last Words

This was an elaborate answer to “What Is A Water Clock And How Does It Work? If you have any related questions, feel free to use the comment section below. And if you want to know why clocks don’t appear in dreams, we have a great article on just that so do give it a click if you are interested “Why don’t clocks appear in dreams? Clocks and dreams!Opens in a new tab.“. Here is also a link about the history of clocks if you want to give that a look “History of timekeeping devicesOpens in a new tab.

AK Iqbal

A University of London’ student with a passion for writing. Clocks have always intrigued me and the importance that they have in our lives is way beyond phenomenal. So, on this site, I write everything about clocks, everything from answering any clock-related queries that you might have along with recommending some of my favorite clocks accordingly. Moreover, I will also be conducting some researches on clock related topics and sharing the things that I learn. So stay tuned to ohmyclock for all the fun clocks related content

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