How Long Does It Take for an Atomic Clock to Set Itself

15 Different Types of Clocks

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For thousands of years, humans have used devices to measure and keep track of time. The current system of time measurement dates back to approximately 2000 BC and the ancient Sumerians. These ancestors sometimes used quite a bit of ingenuity to keep track of the passing day. These days it's very easy to keep track of time on numerous devices, from cell phones to tablets and iPads. Check out 15 of the most interesting types of clocks.

Mechanical Clock

A mechanical clock is made from simple mechanical components that aren't electrical. Usually powered by a coiled spring or falling weights, common mechanical clock examples include grandmother, grandfather and cuckoo clocks. The accuracy of the clock depends on its construction and the engineering of its components.

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Pendulum Clock

A pendulum clock uses a pendulum for time dividing. This improves the clock's accuracy because the swinging has a special property. The length of the pendulum determines the time for the pendulum to swing back and forth. The pendulum's weight and arc don't affect the swinging, resulting in consistent time dividing.

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Alarm Clock

An alarm clock is designed to alert an individual or group at a specified time. The primary function of these clocks is to wake people up in the morning or after naps, but they can be used for other reminders as well. Most use sound, although some alarm clocks use light or vibrations. Most alarm clocks stop automatically after a certain time, or you can manually press a button or handle to stop the alarm.

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Atomic Clock

Atomic clocks are calibrated against the frequency of a resonating atom, usually cesium. As a result, they are highly accurate. The NIST-FI atomic clock at the National Institute of Standards and Technology in Boulder, Colorado, is accurate to less than a second in more than 60 million years. Because these clocks are expensive scientific tools, they are used mostly in laboratories.

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Stopwatch Clock

Stopwatches are used to accurately time events. In fact, they don't record the time of day or night; they merely record how long it takes to perform certain functions. Indispensable in races and sporting events, some stopwatches can time multiple events. Some can even track parts of an event in addition to the total event time.

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Hourglass

An hourglass measures time by allowing sand or another substance to flow between two glass bulbs connected vertically by a narrow neck. This construction allows a regulated trickle from the upper bulb to drop to the lower one. Factors that affect the time interval include sand coarseness, sand quantity, neck width and bulb size. Hourglasses may be reused indefinitely by inverting the bulbs once the upper bulb is empty.

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World Clock

A world clock is a clock that displays the time for various cities around the world simultaneously. It can come in various forms, such as multiple round analogue clocks with moving hands or multiple digital clocks that feature numeric readouts. Some world clocks feature a picture map of the world embedded with digital or analog displays.

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Quartz Clock

Quartz clocks use an electronic quartz crystal oscillator and a frequency divider or counter. This crystal vibrates when electricity passes through it, and the vibration is very consistent, resulting in a very reliable mechanism for time keeping. The quartz crystal and electric circuits are referred to as the quartz oscillator, while the crystal's oscillation is known as the piezoelectric effect.

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Candle Clock

Used in ancient times, a candle clock is a thin candle with consistently spaced markings. When burned, the passage of time is indicated by the level of the markings. These clocks provided an effective way to tell time at night, indoors and on cloudy days.

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Sundial (Sun Clock)

The sundial measures the time of day using the direction of shadows cast by the sun. As the sun moves from east to west, the shadows formed tell the time. The Egyptians were the first to use sundials, and a well-designed sundial can still measure local solar time with reasonable accuracy today. However, it requires the sun to shine and doesn't work at all at night.

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Torsion Pendulum Clock

This type of mechanical clock keeps time with a mechanism called a torsion pendulum. It consists of a weighted disk or wheel suspended by a thin wire or ribbon, called a torsion or suspension spring . The torsion pendulum rotates around the vertical axis of the wire, twisting it, instead of swinging like a regular pendulum. The force created by the twisting torsion spring reverses the direction of rotation. This allows the torsion pendulum to oscillate slowly, clockwise and counterclockwise.

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Astronomical Clock

An astronomical clock is a clock that features special mechanisms and dials to display astronomical information. It shows events such as the relative positions of the moon, sun, zodiac constellations and sometimes major planets.

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Pocket Watch

A pocket watch is made to be carried in a pocket. Consequently, these watches were the most common type from the time they were developed in the 16th century until the advent of wristwatches after World War I. These watches generally have an attached chain that allows them to be secured to a lapel, waist coat or belt loop to prevent them from being dropped.

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Digital Clock

Digital clocks display a numeric representation of time. Two numeric display formats are commonly used on digital clocks. These clocks mostly use a LED or LCD display in either 12- or 24-hour notations.

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Analog Clock

Analog clocks usually indicate time using the angles of the clock hands. The most commonly used clock face uses a fixed numbered dial and moving hands. The clock usually has a circular scale of 12 hours, which also serves as a scale of 60 minutes.

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