We all know about leap years, but did you know that there are “leap seconds” — and that scientists are arguing about whether to keep them?
Leap seconds exist because the Earth doesn’t rotate with absolute precision. It speeds up and slows down as it spins, making some days a few milliseconds faster or slower than others. The problem is that these little spurts and slowdowns put the Earth out of phase with the precise measurement of atomic clocks. Leap seconds were added in 1972 to try keep Earth and atomic clocks in sync. The leap seconds get added here and there, whenever the discrepancy reaches .9 second.
The randomness of the leap second poses problems for systems that require a continuous time reference, like navigation and telecommunications systems. So, some countries — like the United States, Japan, and France — want to get rid of it. Others, like the United Kingdom, Germany, and Canada, want to keep it because they don’t want the Earth and atomic clocks to get too far out of phase.
After vigorous debate, a typical modern resolution occurred: we’ll just defer a decision until 2015. Seems fitting to delay a decision about time, doesn’t it? In the meantime, enjoy well those magical leap seconds — whenever they occur.