New Year’s Eve 2016 – One more second to celebrate…

2016 will be one second longer, so if it feels like a long year this might be the reason….

The International Earth Rotation and Reference Systems Service (IRESS) which is the authority responsible for the measurement and distribution of time is adding one second to 2016. As a result the last minute December 31, 2016 will have 61 seconds rather than the usual 60 seconds. So you will need to wait one extra second after midnight to wish everyone a “Happy New Year!”

Do we really need an extra second in 2016? What would cause this? Leap seconds are needed because the average length of a day is a bit longer than 24 hours due to Earth’s rotation. Without leap seconds, the times of a variety of phenomena such as sunrise and sunset would gradually shift compared to clock time.

The IERSS was established and tasked with keeping clock time in sync with Earth’s rotation. To do this they occasionally have to add “leap seconds” to do so. Leap seconds are added based on actual observations rather than using a formula similar to the one used for leap years because Earth’s rotation isn’t predictable. While the average length of the day is increasing one or two milliseconds per century due to tidal interactions between the Earth and the Moon.

But the actual day fluctuates on shorter time scales because the Earth is not actually a solid body and the crust that we live on is the exception. Most of the Earth is fluid from the convection currents mantle that drive continental drift, to the currents in inner core hat generate Earth’s magnetic field which is why observations are used to correct clock time to match rotation of our planet.

So while you are celebrating New Year’s Eve, just remember 2016 is one second longer than usual.

Shawn Laatsch

About Shawn Laatsch

Shawn Laatsch is the director of the Emera Astronomy Center and Jordan Planetarium at the University of Maine. He started his astronomy education career in 1984 and has directed planetariums in university and science center facilities, taught undergraduate astronomy courses, and given numerous lectures around the globe. He serves as President (2017 & 2018) of the International Planetarium Society, Inc. the world’s largest organization of planetarium professionals. Shawn has a passion for sharing astronomy and stargazing with people of all ages.