Science: Tomorrow is ‘leap second’ day

The bad news is that your Tuesday is going to be a little longer than usual. The good news is that you probably won’t even notice. Tomorrow, June 30th, will officially be one second longer, thanks to the Earth’s daily rotation and it’s pesky unpredictability.

There’s a lot of complicated science to explain why we must add a second to the day – called the leap second – every few years, but the gist is this: because the daily rotation of the Earth is somewhat unpredictable, scientists have to make up for the time lost by adding time to the daily cycle.

Normally there are 24 hours in a day, which translates into 86, 400 seconds. But this number is merely an estimate, notes the online journal, Live Science. The “mean solar day (or the average length of a day) is roughly 86,400.002 seconds long, and according to NASA, ‘this happens because Earth’s rotation is slowing down, thanks to a kind of braking force caused by the gravitational tug of war between Earth, the sun and the moon.’”

There are dozens of factors that influence how long a day is. Factors like weather, oceanic tides, polar ice storage, even El Nino can have an impact, so there has to be a catch-up of sorts. The extra two milliseconds add up until there is enough to make a whole second, and that’s when they decide to add the extra second.

The last leap second was added in 2012, but National Geographic explains, “Leap seconds were first introduced in 1972, and at that point, atomic clocks and astronomical clocks were already off by ten seconds.” Live Science adds, “Scientists record how long Earth takes to fully rotate each day by using a method called Very Long Baseline Interferometry (VLBI)” so when they add that extra time, we know they have done so at just the right moment.

The addition of the second probably won’t affect you very much, unless you keep track of time in micro elements, but it has been known to wreak havoc on computers. National Geographic assures us that even though some programs don’t account for the time jump, “Apple does so on its devices. Google mobile devices sync with Internet time services that are usually tied to atomic clocks. But if you have a standard Windows system, [it] just ignores the leap second.” At least that’s a relief, mostly.

There were some problems, however, in the last leap second addition in 2012, and sites like Gawker, Reddit, Mozilla, LinkedIn and Foursquare had to scramble to work out the time-bugs, reports Live Science. We’re pretty sure they learned a lesson from last time and are upping their leap second game.

In case you want to keep track of the 2015 leap second, watch your clocks at precisely 7:59 PM (EST). You won’t really be able to see it, but you’ll know it’s happening anyway.

(Featured image via Universal Pictures)

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