Editor's Note: This article was written by one of Dr. Rabiah's correspondents for her blog, Tim. This was submitted on his behalf.
Most of us know about leap years, in which we add a day to our calendars at the end of February to adjust for the fact that Earth actually takes 365.242 days to make a full trip around the Sun, rather than exactly 365. But have you ever heard of a leap second?
On New Year's Eve this year, the world's clocks will add a single second to account for differences between atomic clocks like the one pictured below, and astronomical clocks, based on earth's unstable, slowing rotation.