Atomic clocks worldwide depend on accurate time, and typically 24 hours is the amount of time it takes for the Earth to make one rotation about its axis, with one sunrise and one sunset.
Atomic clocks are set by that 24-hour rotation. The problem is, it's not exactly 24 hours, and if the Earth’s rotation slows a tiny amount, global timekeepers periodically have added a leap second to the clocks to keep them in sync with Earth.
Since 1972, we have made this awkward addition 27 times. But what if the rotation speeds up? And…indeed earth's rotational velocity has sped up, affecting the need to add a leap second every few years.
Why is Earth rotation speeding up? Mark Fischetti, a senior editor for sustainability for Scientific American, has written on the topic and explains it all.
