Once You Know It, You'll Never See a Clock the Same Way Again

close-up photo focus on twin bell of a ringing analog clock

Image: by it's me neosiam, via Pexels

Have you ever looked at your wristwatch, paused for a moment, and really appreciated all the craftsmanship that went into making it? The precision of those tiny gears, the springs and other pieces… all working in harmony to keep track of time, down to the very second. But how do all these components function? How does a clock work?

close-up photo of a vintage clock which reads 2:05

via Giphy

Clocks are incredible mechanical devices when you think about it. And their creation didn't just happen over a single night. They are products of centuries of innovation, and the efforts of inventors all over the world.

Maybe you've spotted one of those see-through wall clocks, and been fascinated by all the moving gears. The effect can be almost mesmerizing.

But although they might seem complex, the clock's basic underlying ideas are fairly easily understood.

photo showing the Big Ben Clock Tower in London, England

Image: by Pixabay, via Pexels

So we'll show you how it works, step by step.

The next time you stand in fascination at one of these technical marvels, and some of your friends muse “how does a clock work?” you can blow their minds by responding:

“…well, the force from the weights pulls on the wheels, and that's regulated by the pendulum with the help of the escapement and it all winds up showing you what time it is.”

Seem complicated? By the time you're done with this article, it won't be. But it will be every bit as amazing…

Clock History: Ancient Answers to the Question "How Does a Clock Work?"

The earliest timekeeping devices were nothing like the clocks of today. People in ancient civilizations kept track of time very differently.

There was no standard global calendar, and there was no standard method like the 24-hour system we have today. (Eventually, the 24-hour system did come into use, and it was based on ancient Egyptian astronomy.)

The Egyptians were among the first to measure time in a precise, mathematical way. And they made some of the of the first time-keeping devices: sundials…

Following the Sun

water clock used by Ancient Persians

Ancient Persian clock in Qanats of Gonabad Zibad, Image: Public Domain, by Maahmaah, via Wikipedia

Sundials were among the very first accurate tools for telling time. A sundial would rely on the sun to cast a shadow. Markings on the side of the dial would then show the time. A person could figure out the hour by seeing where the shadow was cast.

As the Earth rotated around the sun, a sundial would need to be rotated too, to keep up with the changing sunrise.

sundial clock

Image: by 466654, via Pixabay

The downside of this was that sundials are pretty useless at night. They're also not great when it's cloudy.

And most of all, you can't exactly put it in your pocket and take it with you.

Imagine having to walk to your town square every time you wanted to figure out how much of the day had passed! Sundials were pretty ingenious back in the day… but not exactly efficient or portable.

Hey Buddy! Wanna Buy an Hourglass?

different style and sizes of an hourglass

Image: by alles, via Pixabay

Another well-known device was the hourglass.

The hourglass had a few advantages to these other inventions. For one thing, it could be carried easily from place to place. But although an hour-glass could help you tell time in the short-term, it also meant you'd need a way of remembering to turn it over every hour, or it would lose track over the course a full day.

There were other devices as well.

graphics showing an old man inventing using the sun

via Giphy

Water clocks used a steady rate of dripping water to move the clock hand. But this rate could be affected by the temperature. If it got so cold that the water froze, you were out of luck.

Candle clocks measured time based on the rate at which a line of candles would burn. But that could also be inaccurate if there were irregularities in the wax. You also generally don't want a clock that can set your house on fire, so a better solution was still needed.

How Does a Clock Work NOW? The First Modern Clocks

the clockface design with zodiac signs found on the Torre dell'Orologio (clocktower) in the Piazza San Marco, Venice

The clockface on the Torre dell'Orologio (clocktower) in the Piazza San Marco, Venice, Image: CC BY 3.0, by Peter J StB Green, via Wikipedia

How does a clock work after so many years have passed? There are some clocks in Europe that still keep time after hundreds of years. Although they have needed some renovations, many of them still contain some of their original parts.

Where Were the Very First Clocks Made?

clock found in the Palais de Justice d'Auxerre (Yonne, France)

Palais de Justice d'Auxerre (Yonne, France), Image: CC BY-SA 4.0, by Francois Goglins, via Wikimedia

The first clock with gears was invented by the Arabs in the 11th Century. Later, in the 15th Century, clock towers began to appear in Europe. Some, like the St. Mark's clock in Venice, you can still see today.

Weight For It...

These early European towers used weights to drive the clocks. A heavy weight would pull down using gravity, and then the clock would employ a series of gears and wheels to regulate that force.

These clocks were often built by monks. The monks needed a way of accurately keeping track of their prayer times. As a result, these clocks were often equipped with a bell that rang on the hour, so that monks would know when to gather. Throughout the 14th and 15th centuries, clock towers were constructed across Europe.

cuckoo wall clocks in different designs and sizes

Image: CC BY 2.0, by Clusternote, via Wikimedia

To this day, many clocks in this style still have bells or chimes. “Cuckoo clocks” and other novelty clocks grow up of this tradition.

The clockmakers added a playful mechanical sequence like dancing villagers or jousting knights as a playful way of showing off their skill. But the underlying idea was still the same: to alert the entire town or monastery at the same time.

I Want One of My Own!

But how does a clock work if it isn't based in a tower? People started wanting clocks that they could have inside their own homes. Gradually they improved on the technology in the towers, and were able to make these clocks smaller.

In this short video, the British Museum examines an early weighted clock to answer the question “how does a clock work?” This shows an older clock, from around this era, when pendulums and batteries weren't being used yet.

The first clocks just had one hand, pointing to the hours. The minute hands and the second hands came later, as clocks got more refined.

During this time, wind-up pocket watches were also developed. The watches would rely on a coiled spring to provide the clock's energy. One such watch was attached to a strap and given to Queen Elizabeth I of England as a gift. This was one of the first wristwatches.

It's All in the Wrist

hanged pocket watches with different styles

Image: by Giallo, via Pexels

Personal watches became popular among the upper classes.

Women often wore wristwatches, although they were seen as fashionable accessories more than tools. Jewelers put a lot of effort into making these wristwatches ornate and eye-catching pieces of art.

Men, on the other hand, typically carried pocket watches, which were more practical. Keeping the watches safe in their pockets protected them from the elements, which could damage them and make them less accurate.


What about Those Grandfather-Style Pendulum Clocks?

The weighted clocks of the Middle Ages were soon the standard. But a big change in clock technology was on its way: the pendulum.

The idea for using a pendulum in a clock came from the famous scientist Galileo Galilei (yes, the same guy who discovered the moons of Jupiter with an early telescope).

Galileo saw that the back-and-forth motion of a pendulum swinging was very reliable. He realized that this regular motion could help keep a clock steadily ticking away.

Unfortunately, Galileo died before he was ever able to create a working model.

hand drawn and painted portrait of Christiaan Huygens

Years later, the Dutch inventor Christiaan Huygens built the first pendulum clock. This was in 1656, and it would change the entire way clocks were made. To this day, the grandfather clocks and wall clocks that many people have in their homes are all based on the Huygens' model.

Image: Public Domain, via Wikipedia, altered

Over the years, the pendulum clock became the standard, and clockmakers and manufacturers made constant improvements to increase the accuracy. After all, aristocrats and nobles wanted the most accurate clocks they could get, and the most precise clockmakers could charge the most.

drawing of Huygens first pendulum clock

Huygens first pendulum clock diagram, Image: Public Domain, by Chetvomo, via Wikimedia

How Does A Clock Work On the Inside?

inside of a clock

Edward VII Memorial Clock Tower, West Parade, Bexhill, Image: CC0 1.0, by Dr-Mx, via Wikimedia

Now that you know some of the history of the clock, let's take a look at the inner workings of a very popular design. We are going on a tour of the inside of a pendulum clock.

If you have one in your home, it is likely very similar to the earliest versions. It may be more accurate and have better materials to address accuracy, durability, and friction. But basically? It's pretty much the same thing.

There are a few obvious pieces when you see a pendulum clock.

Super-Quick Overview of the Pendulum Clock

First, there's the body of the clock. This might be designed to stand on the floor, like a grandfather clock. Or it might be designed to be wall-mounted.

After that, you get that actual components of the clock itself. This is the internal mechanism - the system of gears, wheels, and pins that make the clock keep time.

In its simplest form, the clock translates ENERGY (from a weight or spring) to CONTROLLED MOTION (using WHEELS, an ESCAPEMENT, and a CONTROLLER).

The controller in this case is the pendulum.

Then, the clock translates that controlled motion to a display, or INDICATOR. This is the face of your watch or clock.

Let's look at each of these bits…


It's All in the Wrist

You might notice some weights on your clock. These weights provide the ENERGY to drive the clock. The weights do this by using the reliable, constant tug of gravity to pull on the wheels.

Wheels (or Gears)

numerous clock gears in different design and colors

Image: by Pixabay, via Pexels

Inside the clock are gears, or WHEELS. These wheels translate the energy from the weights into keeping time. The system of wheels that keeps time is called the “going train.”


graphics of an anchor escapement for a clock

Image: CC0 1.0, by Chetvorno, via Wikipedia

No, we're not trying to escape... this is the escapement device.

The escapement is a device inside the clock that rocks back and forth. This is what causes the ticking sound of the clock.

Here's a look at a wristwatch escapement.

graphics showing how wristwatch escapement works

via Giphy

So in a watch, the escapement looks a little from how it might be in a large clock. The watch is powered by a spring (as shown above) rather than weights. But the basic idea is the same.


This is the pendulum, which will be moving back and forth if the clock is working.

graphics showing a pendulum clock

via Giphy

The pendulum might move faster or slower depending on the size of the clock (large clocks will have longer pendulums with more time in each swing).

The pendulum uses its regular motion to regulate the clock. It is like the clock's heartbeat. What really matters here is the length of the pendulum. The motion in a pendulum will be the same regardless of how much the pendulum weighs.


clock running counter clockwise

via Giphy

Lastly, the indicator. This is the face of the clock, AKA what we see when we look at the device, and how we tell time.

Usually the indicator will include at least an hour hand and a minute hand. Modern clocks might also have a second hand, or other additional features.

All Together Now!

graphics showing how the clock runs by seconds, minutes and hours

GIF by theordoregray, via Reddit

Now that you understand the function of each component, you can understand the system as a whole. When you put it all together, you get something like this:

close-up photo of a classic clock which hits 2:05

via Giphy

So on the left you have the pendulum, which regulates the back and forth motion of the escapement. Then you have the weight in the middle, pulling on the wheels.

(And it's here you can see how, if you didn't have the pendulum on the left, the weight would pull down all at once. The whole operation would be over in just a few seconds, and that wouldn't be useful at all.)

Finally, all that predictable motion winds up driving the wheels on the right, which are attached to the hour and minute hands.

And the result of all that science and innovation?

Tick… tick… tick…

You get a machine that accurately tells time, day in and day out.

Seriously, this is making me nerd out a little. Think of all the people who contributed to the creation of this device!

People from ancient civilizations, Arab inventors, medieval monks, Galileo Galilei, and Christiaan Huygens ALL pitched in to develop this piece of machinery that now sits in countless homes. Not too shabby, humanity… not too shabby at all…

Break It Down

great wheel skeleton clock

Image: CC BY-SA 4.0, by Rauantiques, via Wikipedia

Now that we've put it all together, let's break it!

(No, really, let's not. Clocks are amazing.)

But really… how does a clock work for so long? With so many bits and pieces, shouldn't they break eventually?

old clock in Salt Lake City, Utah

Old clock in Salt Lake City, Utah, Image: CC BY-SA 2.0, by Ken Lund, via Wikimedia

So Many Parts

Well, clocks do break down sometimes. Because every piece is vital to the functioning of the clock, if one piece is off by even a little bit, the whole thing can start losing its precision.

As clocks became more refined, efforts were made to lower the amount of friction that takes place inside a clock. This helped keep them more accurate.

But even with all of these efforts, a clock will occasionally need to get a touch up, just like your car engine. If it has moving parts, you can bet that it's going to need a good fix-up at some point.

The first task in fixing any problem is identifying it.

So if you have a clock that's busted, you need to have a good handle on the basics (which we've just covered). That way you will notice what isn't working the way it's supposed to.

Really Got Your Clock Cleaned, Didn't You?

Many people start out by opening it up, taking a look, and maybe cleaning it.

The process is painstakingly exacting, and requires precision with many tiny pieces. Watch as our friend opens up the antique clock from before:

Often, you'll find that the problem is that something has gummed up the works. One of the gears might have gotten something stuck to it, and the extra bit of friction has changed the regulation of the time.

If that happens, you want to clean the pieces of the clock. Depending on how old or valuable your clock is, you might want to take it to an expert who won't damage it in the process. Older clocks need specialized care, so if it's an antique clock, talk to someone who understands that type of antique before trying to clean it yourself!

A Well-Oiled Machine

Clocks will also need to be oiled in order to keep working. This greatly decreases the overall friction between the moving parts (although you can never eliminate friction entirely). You'll want to get special clock oil in order to do this; don't use just anything.

Ok, so we've looked at keeping your pendulum clock in good health. But here's another question for you.

How does a clock work when you can't use gravity as its energy source? Is that even possible?

Turns out, yes, it is…

Shake It Up! Keeping Time with Quartz

Church clock in St. Mark's Square in Venice, Italy

Image: by ildigo, via Pixabay

With the creation of the pendulum clock, people finally had a way of telling time that was accurate and required minimal attention. That is to say, with the amount of weight you can attach to a pendulum clock, it's possible to set the weight and then let the clock run for at least a week.

However, people always are looking to improve on what they've got. And another big change came after the adoption of battery-powered wristwatches.

What inventors came up with here was a completely different type of control mechanism.

This time, it was the mineral quartz.

Quartz is a naturally occurring crystal. It isn't expensive, but it does have a few priceless qualities. One of those how it responds to electricity.

If you take a battery and shoot a tiny bit of electricity through quartz, the quartz will vibrate. What's more important, it vibrates at a precise rate, so it is always the same.

If you're curious: every second, it vibrates 32,768 times.

Like with the pendulum, it's totally consistent. That means that it can be a reliable way of controlling a time-keeping device.

a collection of men's watch intact inside a box

Image: by Hugo Filipe, via Pexels

In a quartz watch, a microchip monitors the vibrating quartz. It then counts up the individual oscillations at a high speed. Every time the counter reaches 32,768 (once a second, exactly), the chip sends an electrical impulse that moves the second hand just one tick.

Many of the wristwatches you see nowadays use quartz to control their accuracy. The battery supplies electricity to the quartz, and the net result is a watch that doesn't need gravity, doesn't to be wound, and is incredibly accurate.

All in Good Time

So congratulations! You're now an expert on the mechanisms that drive clocks. Now you can wow your friends, and appreciate just how much genius went in to building these devices to begin with.

Just to recap. All clocks need:

  • ENERGY: A power source. A battery. A weight. Something to drive the motion of the clock itself.
  • CONTROL: Some way of regulating that energy and metering it into precise beats.
  • INDICATOR: A way to translate that constant beat into information that humans can see, hear, or understand.

Whatever type you use for your own time-keeping, you won't be taking it for granted. Not any time soon, anyway!

a loop of spiraling clock

via Giphy

Featured image: by dassle, via Pixabay

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