Subscribe

Search

What is a Leap Second?

Do you know the next leap year is 2020? But, do you know what is a leap second and when will that be?

Similar to an extra day added to the calendar every leap year, an extra second is added to our atomic clocks at the stroke of midnight usually on the last day in June or December at select intervals – the leap second. A leap second is a one-second adjustment that is occasionally applied to the Coordinated Universal Time (UTC). Guess when the next leap second insertion is supposed to occur?  It's 23h59m59s on 31st December (UTC) this year – depending on where you are, you might have to count down one more second before ushering in a brand new 2017! (PS, the leap second occurs at 07h59m60s on 1st January 2017 in Singapore).

 

So what's the point of adding an extra second to our clocks? You see, scientists have discovered that the Earth's rotation has been slowing gradually over time. While planetary systems cannot be controlled, atomic clocks functioning on the vibration of atoms that act like the pendulum of a grandfather clock provide an extremely stable and accurate way of measuring the length of a second.

In contrast to the pendulum of a clock which is prone to timekeeping errors arising from manufacturing variations, temperature and material, scientists found that atoms of the same element will oscillate at exactly the same rate. This eradicates all room for errors and finally in 1967 – caution: nerdy numbers coming up – the standard definition for a second was decided as 9,192,631,770 oscillations of a Caesium-133 atom! The leap second insertion derived from the function of atomic clocks thus serves to sync the Earth's rotation with atomic clocks, compensating for the Earth’s irregularities!

 

 

Perhaps to you and me, one single second doesn't make a dramatic difference to our daily lives. (After all, it's just ONE second that doesn't make a difference to your project deadline or an already burnt piece of toast.) However, for Global Positioning System (GPS) satellites that send time signals every second to ensure that ships and planes do not have clashing routes, the tiny measure of a second can certainly have an immeasurable impact!

This is because even an error of one microsecond could translate to a difference of 300m on the road – we wouldn't want such a discrepancy when waiting for our Uber driver while staring at our GPS map that otherwise indicates that the driver has already arrived but is nowhere to be seen, would we? Likewise in the financial sector where stocks are traded in fractions of a second, one full second could mean the difference between a successfully received order registering hundreds of thousands in profits or losses!

 

 

In Singapore, A*STAR’s National Metrology Centre (NMC) is our custodian of time, maintaining an ensemble of atomic clocks that count among more than 400 other clocks in the world. Together, these atomic clocks are part of a global network of time transfers that contribute to the calculation of a standardised international time known as the "Coordinated Universal Time (UTC)”. A time transfer is a scheme through which multiple geographical sites share a precise common reference time. Without a universally agreed upon time, imagine the amount of chaos and confusion there would be at airports or on screens where televised Olympic matches are supposed to air!

 

Apart from timekeeping, NMC also maintains the accuracy of Singapore’s physical measurement standards including weight, temperature and length. This laser precision provides  industries such as aerospace, energy and MedTech with well-defined solutions leveraging on cutting-edge measurement technologies.

In the same way Rolex is to the Formula One Grand Prix, NMC is Singapore's official timekeeper. Working quietly behind the scenes of our everyday lives, NMC is our silent guardian of time, perfect to the last second.