The Leap Second

It received some news coverage, but nothing really major. At the end of 2005, there was a leap second that was added to analog clocks to get them caught up with atomic clocks.

To understand this, you must first know that there are currently two time-keeping systems in place for the civilized world.

Analog clocks are kept and maintained by measuring the Earth’s cycle around the sun and the Earth’s rotation on it axis, just as has been done for thousands of years.

The problem with analog, however, is that each time the Earth revolves around the sun, there is an average discrepancy of a half-second each year. In addition, each day is actually not exactly as long as each other due to the pulling of the tides on the Earth’s rotation which cause fluctuations of milliseconds.

Realizing that there was a problem with this analog time keeping, scientists developed a new method called the atomic method some 40 years ago. The atomic method uses the measurement of the extremely accurate and precise cycle of an atom of the isotope cesium-133.

In one second, the atom cycles 9,192,631,770 times. This cycle is constant, never varying and means that a half-second variance like the one that occurs in analog time each year, occurs only once every 10 million years in atomic time.

Since 1967, because of the variance in the two time-keeping methods, mankind has had to add a leap-second to analog time 23 times to ensure that the analog clocks and the atomic clocks are in sync to the tune of no more than a 0.9 second variance.

Why is it important to keep the clocks in sync? Well, if we stopped adding the leap seconds today, in the year 5000, the sun would be right overhead at noon, but your atomic clock would say it was getting close to midnight.

So, what’s the problem with leap seconds? Well, remember Y2K? There are some folks that believe if we keep stopping our atomic clocks for one second intervals every couple years, it will cause wide-spread system failures in the flight control, traffic control, power grids, mobile phone networks and defense systems that are all tied to atomic clocks.

For example, if a GPS satellite sends a signal a millisecond early or late, it can provide a reading that is inaccurate by 100 miles. You do not want a ballistic missile being 100 miles off its target.

So, for now, while scientists debate the best method, atomic clocks continue and the old-time Earth-monitoring analog time continues, both being continually checked against the other.