Have you ever felt that time is slipping away from you? Well, then you’ll be happy to know that today is Leap Second Adjustment Day, a day when time will be held back for a second, with an extra second being inserted into the atomic time scale at midnight, June 30 UTC (Co-ordinated Universal Time). This time corresponds to noon, July 1 in New Zealand. To mark this moment, Radio New Zealand listeners will hear an extra time ‘pip’ before the midday news bulletin.
The rotation of the earth is gradually slowing down, effectively resulting in our days becoming fractionally longer. Hence the adjustment is required to prevent the atomic clocks from moving ahead of solar time. Leap second adjustment was introduced for the first time in 1972. It does not happen every year, with the decision being made by the International Earth Rotation Service, based on data collected from observatories around the world. Leap second adjustment has been done 24 times over the past 40 years.
In earlier times, time was measured by the position of the sun and stars in relation to the earth, so the slight slowing of the rotation of the earth was automatically accommodated for. However, since time measurement has changed to atomic time, which uses the pulsations of the atoms of the chemical element caesium, time measurement has become, weirdly enough, too accurate. Time can now be measured down to 10 billionths of a second, and only one atomic second is lost every 300 million years, so to keep time in sync with the slightly irregular movements of our solar system, its necessary to make an adjustment every now and then.
When the leap second is added, the atomic clocks will not go from 11:59:59 directly to 12:00:00, but rather to 11:59:60, and then 12:00:00. As a result, the day on which the leap second is inserted has 86,401 seconds, instead of the usual 86,400.
Hmmm, wonder what I’m going to do with all this extra time!?