The world is doing away with the leap second

DAVID FOLKENFLIK, HOST:

It already feels like we don't have enough time. But the world will soon lose something called the leap second. That decision was made at the 27th General Conference on Weights and Measures earlier this month in Paris. So let's drill down on leap seconds and why we're getting rid of them. The man who can lay down some knowledge - that's NPR science correspondent Geoff Brumfiel. Hey, Geoff.

GEOFF BRUMFIEL, BYLINE: Hi, David. So I want to ask you the first question here, which is - I mean, have you ever wondered where seconds come from?

FOLKENFLIK: This weekend, I'm assuming pretty much from the stovetop, but I think you mean something else.

BRUMFIEL: (Laughter) Yeah, I do. I mean the official second that we all use here in the U.S. - it turns out that it's made in Boulder, Colo., at the National Institute of Standards and Technology. They have more than 20 atomic clocks spread across the campus. And then there's this one windowless room where they take all those clock signals, all the ticks, they bring them together, average them out, and in the corners, this little flashing green light.

JEFF SHERMAN: You're seeing the seconds as they're made. And every flash is the beginning of the second in the U.S.

BRUMFIEL: That's Jeff Sherman. He's the physicist in charge. And he was showing me around actually earlier this month. His second is broadcast across the U.S. And also it's used to make the global second. It's averaged together with 80 other countries' seconds. This is all agreed to by the 1875 Treaty Of The Metre.

FOLKENFLIK: So where do leap seconds come in?

BRUMFIEL: Right. So the Earth's rotation changes over time. It's slowing down ever so slightly because of the moon's gravitational pull. The upshot is every few years, give or take, the International Bureau of Weights and Measures in France has to add a leap second. In other words, for one minute of one hour of one day, the clock counts an extra second.

FOLKENFLIK: So if that keeps us in sync with the Earth, why would you want to get rid of it?

BRUMFIEL: Yeah, I mean, it makes sense, right? It kind of helps us all keep in sync with our planet. But it turns out the seconds set out by the world's labs get used in a lot of other ways you might not expect. So, for example, your cell phone is running off that time. So is the network that your cell phone uses and GPS.

SHERMAN: Underneath all the modern conveniences that we like and enjoy is infrastructure like this keeping synchronization across distances.

BRUMFIEL: And the timing really matters, especially for things like computer servers that run the internet and GPS. They need very precise time.

FOLKENFLIK: And if you insert rando seconds into the system, it messes things up.

BRUMFIEL: Totally - that's exactly what's going down. So in the past, leap seconds have taken down airplane reservation systems. In fact, tech companies really don't like the leap second. It just is a mess for them to deal with. And the U.S. government actually agrees. As computers and GPS and all these other systems become more precise and more a part of our lives, putting these random seconds in is just starting to cause more problems than it solves.

FOLKENFLIK: But what do we lose by getting rid of it? What's the unintended consequence here?

BRUMFIEL: Well, astronomers are going to lose out because the Earth's rotation will no longer be matched with the official time scale. But other than that, there's not that much that will change. It turns out they're still going to sync up the Earth with our clocks, they'll just do it once every 100 years, maybe by inserting, say, a leap minute. And for now, leap seconds are sticking around. The new system won't be in effect until 2035. So if you want to catch a leap second, you can.

FOLKENFLIK: We've been hearing from NPR's Geoff Brumfiel. Geoff, thanks.

BRUMFIEL: Thank you, David. Transcript provided by NPR, Copyright NPR.