When the power goes out and is later restored, how do you know what time to set your clocks to? Have you ever wondered how time is regulated? In the U.S., the standard of time is regulated by the US Naval Observatory's Master Clock (USNO), the official source of time for the Department of Defense. The effects of these mechanisms are felt by all of us in the form of our alarm clock, computers, answering machines, and meeting schedules. In this edition of How Stuff Works, we will learn all about atomic clocks and how they keep the world ticking!

Go to the next article about How Atomic Clocks Work or pick from the table of contents:

• Introduction to How Atomic Clocks Work You are here
• Are Atomic Clocks Radioactive?
• What Are the Types of Atomic Clocks?
• How Does a Practical Cesium Atomic Clock Work?
• When Was the Atomic Clock Invented?
• How is Atomic Time Measured?
• Links
• About the Author

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