You’ll actually have an extra one today.
Google (Xetra: A0B7FY – news), for example, is adding on fractions of a second to its systems throughout the day.
A typical day consists of 86,400 seconds in UTC time.
The extra second is called a “leap second”. NPL says that the United Kingdom Government believes that the consequences of breaking the link between civil time and the Earth’s rotation are not fully understood, and that the problems leap seconds now cause can be dealt with by technical improvements.
“The difference of 2 milliseconds – far less than the blink of an eye – hardly seems noticeable at first”.
However, the planet´s unpredictable exact rate of rotation means they can not be predicted and programmed in advance, making manual adjustments necessary.
So where does the extra second come in?
Atomic time – because it is so accurate – can occasionally move ahead of the earth’s actual rotation. An extremely precise methodology is used to do so: the Very Long Baseline Interferometry (VLBI).
“A leap second is a second added to Coordinated Universal Time (UTC) in order to keep it synchronized with astronomical time”, explains the National Institute of Standards and Technology.
All kinds of events affect the speed of the Earth’s rotation, including large weather systems, atmospheric winds and even the changing of the seasons.
Leap seconds can be added in June or December, according to IERS.
While many celebrated the “longest day of the year” on Sunday, June 21, as summer officially kicked off, the length was referring to the number of daylight hours, not solar time.
But it is feared the leap second could cause problems for some computer systems. Shortly after 7:59:59 PM, the Susquehanna Valley (and the entire world) will be subject to an extra “leap second“, adding one second to all the planet’s clocks.
The leap second to be added tomorrow will be the 4th one inserted since 2000.
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