Why June Will Be 1 Second Longer

PHOTO: An extra second will be added to the last minute of June 30, 2015.

An extra second will be added to the last minute of June 30, 2015. Getty Images

It’s a dreaded day for many Internet companies: On June 30, an extra second will be added to the clock, creating the potential to wreak havoc on computer systems not equipped to handle the change.

Because Earth’s rotation is slowing ever so slightly, we occasionally need to add an extra second to re-sync our super-precise atomic clocks to our planet’s rotation. Strictly speaking, a day lasts 86,400 seconds. However, the mean solar day – the average length of a day, based on how long it takes the Earth to rotate – is about 86,400.002 seconds long.

This difference of two milliseconds, or two thousandths of a second – far less than the blink of an eye – hardly seems noticeable at first. But if this small discrepancy were repeated every day for an entire year, it would add up to almost a second.

But you know who’s not on board with all this? Those damn computers, whose operating systems just can’t handle it. The last time we added a leap second in 2012, it wreaked havoc across the Internet. When the last leap second was added on June 30, 2012, it caused issues with a number of websites, including Qantas, LinkedIn and Yelp, according to reports at the time.

Leap seconds are governed by the Paris-based International Earth Rotation Service, which this week announced its plan to make June 30, 2015 one second longer. This will be the 26th such leap second added since 1972. This June’s leap second will be only the fourth to be added since 2000.

In those intervening decades, though, we’ve become ever more dependent on computers and GPS systems that need to keep exact time—making the task ever more fraught. In 2012, the act of adding a simple second took down Mozilla, Reddit, Foursquare, Yelp, LinkedIn, and StumbleUpon, according to the Telegraph. And yes, Gizmodo was not spared either.

It mostly has to do with NTP, or the Network Time Protocol computers use to sync with atomic clocks. If a computer sees the same second twice in a row, it logically thinks something went very wrong. There are fixes to this, but they’ve obviously not been implemented across the board.

Apparently, the Telegraph reports, there’s been some controversy over whether to keep adding leap seconds. U.S. delegates have argued that “precisely timed money transactions could go astray or vehicles could be sent tens of metres out of position if they are a second out in their measurement of time.” It’s amazing to think that our world is so interconnected but fragile that a single second could send hiccups rippling through the system.

But, perhaps, more frighteningly, if we don’t keep adding leap seconds, the primordial link between our notion of a day and the rotation of the Earth could be forever disrupted. Experts also fear that once this link is broken it could never be restored because although the Earth’s timekeeping systems are built to accommodate the occasional leap second, adding a leap minute or hour to global time would be virtually impossible.

After all, what is a day? Is it 24 hours exactly? Is it one complete revolution of the Earth? Armed with our super-precise modern instruments, we find ourselves asking basic questions about our world.  Source: The Telegraph

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