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Taking the great leap

Gabriel BorrudJune 30, 2015

"And you run and you run to catch up with the sun, but it's sinking!" Once again, Pink Floyd knew it best: the earth is slowing down. But there's a way to fix it. DW looks at questions and answers around the leap second.

Image: Joe Raedle/Getty Images

On Tuesday, June 30, the night will be a tick longer - but, unfortunately, that doesn't mean you can party on or sleep in, because that literally means just one tick.

What's going to happen?

Instead of flowing from 23:59:59 to 00:00:00 like always, the atomic clock that sets Coordinated Universal Time (UTC) is going to jump to an aberrational 23:59:60 before heading into Wednesday.

From a procedural perspective, it's quite simple: one second is going to be added to the day on Tuesday.

Who - or what - determines time?

UTC is the standard timescale by which the world's clocks are regulated, and it is determined by international standards organizations including the International Bureau of Weights and Measures (BIPM), and the International Earth Rotation and Reference Systems Service.

We've come a long way from the sundial, but these organizations still - at least theoretically - use the sun to determine time. The units with which we measure time today are all based on the amount of time the earth needs to make one full rotation on its axis. That's 24 hours, or 1440 minutes, or 86,400 seconds.

However, because this amount of time is perpetually changing, scientists came up with a way to standardize the second, based on the radiation of the atomic element cesium. As random as this seems, it's not. The time it takes cesium 133 at its ground state to complete 9,192,631,770 periods of radiation corresponds to exactly one second.

But there's a problem. Andreas Bauch, who works at Germany's National Metrology Institute - the federal laboratory in charge of the measurement of time - summarized it best: "The atomic second just isn't long enough."

Weltall Erdumlaufbahn
Compared to the radiation frequency of cesium 133 at zero degrees Kelvin, the speed of earth is slowing downImage: REUTERS

So the earth is slowing down?

The average solar day is about 86,400.002 seconds long.

That .002 means that UTC is drifting away from solar time, ever so slightly.

Every year, the earth drags its feet compared to the speed it should spin - according to the atomic clock. As soon as the difference between the two approaches 0.9 seconds, compensation has to be made, i.e., the leap second.

This is nothing new to science, but it can be a rude awakening for the technological world.

What can digital systems dependent on UTC do to compensate for the leap second?

There are two options. Either let their hair down and do nothing, like the great majority of companies have done on leap-second years in the past.

This proved annoying in particular for digital systems based on Java and Linux (Reddit, LinkedIn, Mozilla, to name a few biggies) the last time around, with companies complaining that these UTC-dependent systems simply couldn't deal with the extra second.

Reports from 2012 said LinkedIn and Reddit were down intermittently after the transition happened.

To deal with the extra second, there is a relatively intuitive way for companies to circumvent the problem: Just shut down your entire system for exactly one second. This is apparently possible, and it's what many companies say they are planning to do.

Will this leap second be around forever?

That remains to be seen. And it will be debated later this year at an international conference of metrology and radio communication in November. The convention will address the implications of severing the atomic clock from solar time. If the rotation of the earth stays constant with what it is now, the atomic clock will be one minute too fast in 100 years.

Speaking temporally, we will be perpetually skewed.

Not necessarily screwed, but definitely skewed.