The hour hand is the slowest to rotate, requiring **twelve hours** (half a day) to complete one full circle. It begins at midnight, rotates once until it is pointing at "12" again at noon, and then rotates one more till it is pointed at "12" again at midnight the next morning. This leaves the hour hand spinning at a rate of one rotation every 12 hours.

The minute hand travels faster than the hour hand, requiring sixty minutes to complete one full rotation. It starts out pointing at "0" on the clock face and then proceeds to sweep back from "9" to "0", and then from "3" to "0", and so on until it returns back to "0" again where it stopped. This means that if you were to watch the minute hand continuously, it would travel back and forth between "0" and some other number in less than an hour.

An individual hand can be seen as a point in space, but only when it is moving. When the hand is at rest, it covers **about two-thirds** of the circle. This is why even though both hands are always rotating, they cover different areas of the clock face.

A hand is made up of **three parts**: the wrist, the palm, and the finger tips. The wrist is the part that connects the arm to the body. It contains **several bones** that allow us to lift objects over our head and use our hands for grasping things.

- How many hours is a hand?
- How many degrees does the hour hand make in a day?
- How many full rotations of the minute hand are there in 7 hours?
- How many turns does the hour hand take in 12 hours?
- How many rotations will the hour hand make?
- How many degrees are there in the angle between the hour hand and the minute hand?

In **12 hours**, the hour hand turns 360 degrees. 5 minutes equals 112 hours. The hour hand makes one complete rotation every 24 hours.

A day is made up of 24 hours. And **the minute hand** rotates once per hour. In a single day, the minute hand completes **24 revolutions** around the clock. So, in order to see how many full rotations of the minute hand are contained in 7 hours, we simply divide 24 by 7, which yields 3.6.

Minute hands on clocks often have from 1-4 numbers radially arranged around their shafts. These numbers represent the minutes past or future an observer would find themselves if they were standing at the appropriate place on Earth at **local sunset** or sunrise. The number of minutes past or future global sunset or sunrise is called the time zone, and the map below shows the current time zone for several cities around the world.

Time zones were first introduced by George V. Schley of the United States Department of Commerce in 1872. He proposed that each country should select a single point on its border and declare that this be its official time. The rest of the world would then follow suit by selecting its own time at the same moment. This plan was adopted by most countries but it took years to implement. Today, time zones are used for administrative purposes, but people within them can still find out what time it is in their city by looking at their clocks.

A conventional 12-hour analogue clock's hour hand rotates 360 degrees in 12 hours (720 minutes), or 0.5 degrees each minute. In 60 minutes, the minute hand turns 360 degrees, or 6 degrees each minute. Thus, the two hands cover the same distance in an hour marker on the clock face six times per day.

This is also true for **digital clocks** with **a minute hand** and an hour hand. The minute hand of most digital clocks in North America turns 60 times per hour, while the hour hand turns 30 times per hour. In **other words**, the minute hand travels 6 hours while the hour hand travels 2 hours during **a single day**. This is why it is important to check both the minute and hour digits on your clock throughout the day; if one of them is off by even just a few seconds, you have gone too far or not far enough from true time.

The first clocks had only an hour hand. They were called "solar" clocks because they told the time of day by looking at the position of the sun. Such clocks were used as long as there was no electricity available for lighting at night. The modern mechanical clock took over from the solar clock around 1750. It used weights instead of sunlight to tell time.

The first electric clocks began appearing around 1900.

In **72 hours**, the hour hand of any modern 24 hour format clock completes 6 complete revolutions. This means that the hour hand will travel 18 miles if the clock is not stopped.

This may seem like a lot, but it's actually only about half as much as you might think: The average human body has a total length of about 63 feet (19 m), and the radius of the earth is about 6300 miles (10400 km). That means that the hour hand travels around 9/5ths of the way across the world every day!

The hour hand of a clock can be moved by an internal or external mechanism. With **an internal mechanism**, the time is displayed on **an enclosed face**, which turns to reveal **new information** when the hand is rotated. With an external mechanism, the time is shown on a separate piece attached to the clock with a cord or chain, and the position of the hand can be seen through a window or dial panel.

Both internal and external clocks need to have their hands adjusted periodically to ensure they are turning at the correct speed. An internal clock needs to be checked regularly, while an external one does not.

The minute hand rotates 360 degrees in **60 minutes** (or 6 degrees every minute), while the hour hand rotates 360 degrees in 12 hours (or 0.5 degrees in **1 minute**). Therefore, the hour hand completes a full rotation every 12 minutes and the angle between **the two hands** is 45 degrees.

This example shows the difference between an angle measured from **one fixed point** to another and an angle measured between two fixed points. The angles in this example are all measures from north to south. Minutes North is 90 degrees east of North. **Hours North** is 120 degrees east of Minutes North. Degrees North is 135 degrees east of Hours North.

Here are two ways to find out what time it is: Using a Clock with Two Hands, you can see that it is 5:30 PM. If you look at your watch right now, it is 5:29 PM. There are 20 minutes left in the hour and 30 minutes left in the day.

Using a Clock with Only One Hand, you can see that it is 5:30 PM too. Your watch says 5:29 PM so there are still 21 minutes left in the hour and 31 minutes left in the day.

You can also use trigonometry to figure out how many degrees there are between the two hands.