Clocks have been around for nearly 2000 years. They first appeared in Europe during the medieval era and became widespread during the 14th century. But how do they work?
A clock is an instrument that measures time according to regular motion; most people are familiar with clocks that use moving hands or numbers to show this information, but there are also clocks whose measurements are based on sound (e.g., bimetallic bell chimes) or water (astronomical regulators).
Clocks may be analog (with gears and hands) or digital (with numbers), atomic, electromechanical, or electronic – but all share a common goal: turning complex movements into simple information about the passage of time.
For example, watches, which are small clocks worn on the wrist, typically show the time in digital format, with two numbers showing hours and minutes. In addition, there are many different types of watches that use various materials for cases and bands; they may perform calculations, play music, or even indicate temperature.
What are the different parts of a clock, and what do they do?
The different components of a clock are:
- Face or dial – shows the numbers and hands, which indicate the time. It is usually made from glass to avoid it being damaged by dust and moisture.
- Hands – these show the time on a clock face. In mechanical clocks, they are attached to the central spindle that turns per changes in air pressure (caused by an open window, for example) and turns the gears inside. A small gear on one end of the hand’s shaft attaches directly to another gear attached to a larger gear with 12 teeth; this goes around once every hour and causes another smaller gear at its center point to move forward one tooth every minute. There is no separate hand on watches and digital clocks; the face moves around to indicate time.
- Mechanism – this is what makes all of the parts move. Mechanical clocks are wound up every day, quartz watches are recharged with electricity generated by sunlight or movement of the body, and digital clocks are either plugged into an outlet or run on batteries.
- Gears – these make separate parts move at different speeds so that they complete one revolution per hour (in mechanical clocks) or units of time (in quartz watches). The gear ratios decrease as their diameter increases; for example, a minute hand may have 58 teeth that rotate once every hour, while a second hand might only have 18 teeth that rotate once per minute.
How does the clock mechanism work?
The clock mechanism consists of a central spindle that turns following changes in air pressure (caused by, for example, an open window) and causes the gears inside to turn. The position of these gears determines which numbers will point at the face at any given time.
What powers clocks – is it batteries or electricity?
Clocks may be powered by:
- Mechanical energy, such as winding a weight-driven clock or swinging pendulum – for this type of clock, the source of power is stored kinetic energy. The fastest clocks in the world use this method and record time with an accuracy of about one second per year (most digital watches and computers keep much better time). The downside to mechanical clocks is that they must be wound regularly or stop running; once their power is gone, it cannot easily be restored.
- Electrical energy from batteries – quartz watches are rechargeable using either light (solar) or movement (automatic) as a power source. Modern versions usually need to be charged every few months, but some types can stay charged for
How accurate are clocks, and how do they stay synchronized?
The accuracy of clocks is determined by how rapidly they can perform their measurements. For example, mechanical clocks are less accurate than quartz watches because the various components (gears, spindle, etc.) must be finely made and precisely placed to ensure that they turn correctly; this takes more time than quartz watches since the movement of gears is caused by electricity. As for staying synchronized, digital clocks use an atomic clock signal transmitted via satellite or radio waves which causes them to reset themselves at a certain point every day.