If you look around your home, you'll likely find several timepieces of varying sizes. From the watch on your hand to the grandfather clock in the living room, and from the alarm clock in your bedroom to the computer clock on your desk, most people have several clocks available. And at any given time, few of those clocks will show precisely the same time. So how do you know which is really correct?

There are several ways of keeping time. The most commonly recognized is based on the Earth's movement through space. But those rotations are very large and the potential for gaining or losing seconds is incredible. A more precise method of timekeeping is atomic time. Very simply, atomic time measures the pulses and absorptions of electromagnetic waves. Generally, atomic time is considered to be the most accurate available.

When you choose an atomic clock, the clock's time is kept current through the use of radio signals between the nearest atomic time-keeping device and your clock. There are several of those devices around the world, including on in Colorado that controls many of the US atomic clocks.

Atomic time keeping has been around for more than a half century, but it's only been over the past few years that the technology is generally available at a reasonable price to the public. The first few atomic clocks were very austere models, meant to be accurate time keeping devices and nothing more. Today, there are plenty of options if you're looking for accuracy without sacrificing beauty.

Grandfather clocks are one of the most recent advances in atomic clock technology. Because these clocks depend on the swinging of a pendulum to keep track of time, they are notorious for gaining time right after they're wound and losing time as the clockworks run down. Some grandfather clocks no longer depend on the pendulum for timekeeping, making them more accurate. But more recently, the atomic clock works have been incorporated into grandfather clock cases. As is true with all atomic clocks, the atomic clocks in grandfather clock cases are periodically updated to be kept completely accurate.

Most people tend to truly believe that computers are right. After all, computers know the time and date automatically, right? But remember that someone set that date at the beginning of the computer's life, and that you may even have adjusted the time for daylight savings time at some point. If you want your computer clock to be always accurate, you can download a program that will have your computer periodically check in for the official atomic time in your time zone.

Over the ages, people have developed many methods and utilized many concepts for determining time. Sundials and hourglasses can give an idea, but are something less than accurate. Rotation of the sun, locations of stars and the rise and fall of tides have all been used to help account for the passage of hours, though they weren't accurate enough to count minutes or seconds. The atomic clock is man's latest step toward keeping an accurate track of time.