A duel at high one, instead of high noon? It just doesn’t sound right, but 1 p.m. might eventually be when the sun is at its highest in the sky — what we know as noon — if U.S. officials and scientists at the U.S. Naval Observatory convince the world to get rid of the leap second, which is used to coordinate universal earth time with the length of a solar year.
In November, the International Telecommunication Union (ITU) will meet to decide whether to abolish the tiny leap second. Of course, that change in noon wouldn’t be noticed for about a thousand years, but the ongoing conversation about whether or not we really need the leap second has taken on greater urgency, as we rely on increasingly on computers, which depend on synchronized time to work.
Demetrios Matsakis, chief scientist for Time Services at the U.S. Naval Observatory, discusses leap seconds with Here & Now’s Robin Young.
Interview Highlights: Demetrios Matsakis
Why do we need a leap second?
“The short answer is it exists because the earth is a lousy clock. The earth speeds up and slows down from one day to the next and over a long time, the earth is slowing down. About 470 million years ago, a day only was 21 hours long.
Who decides when leap seconds are added?
“It’s done by a group called the IERS [International Earth Rotation and Reference Systems Service]. It’s based on observations from radio astronomy. We have antennas set up around the world that look at the most distant objects we know, which are quasars, and we see them appearing to rotate, but it’s the earth that is rotating differently than we expect it to be. We measure the difference between the rotation of the earth and the atomic time. The IERS watches that difference grow. And when they see it start to exceed nine-tenths of a second, they insert a leap second.”
Would this cause problems with computers?
“We have the modern version of train crashes, this would be crashes on the Internet. A lot of programmers don’t even know that leap seconds exist. I venture to say the vast majority of the world doesn’t know that leap seconds exist and they still think we operate on Greenwich Mean Time, although Greenwich Observatory has been closed for decades. Leap seconds are inserted, the computers get a mismatch, and the mismatch can lead to the computer shutting down saying ‘the time is wrong I can’t operate.'”
What problems have occurred in the past?
“The last time we inserted a leap second was June 30, 2012. At that time, the computers that were controlling the reservation system for Qantas Airlines in Australia shut down and passengers were stranded by the thousands at airports until that problem was fixed.”
Good thing it was just reservations and not flights
“You’re right, Robin. The GPS itself will give good time. GPS is well designed – its signals can handle the leap second. But GPS receivers, what the user has, can be misprogrammed and have been misprogrammed. GPS receivers have not taken in the leap second right. And if you have an error of 1 second, 1 leap second, it could cause a positional error of 1,000 feet. That’s why this group called the Civil GPS Interface Committee passed a resolution last August calling leap seconds a hazard to navigation.”
What’s the resistance to getting rid of the leap second?
“The resistance is political and most of it comes from the U.K. All of their public releases report time as GMT, even though the time is coordinated universal time – UTC. Since the two never deviate by as much as 9/10 of a second, it’s a good approximation, so that’s a great source of national pride. If you look at their tabloids, which are the subconscious of a nation, they say that time is up for Britain, that time will drift towards the U.S. That came from their minister of science.”
What will happen in the next 20 years, if we do nothing?
“Well, we call it a scare story, and I give public talks where I ridicule the consequences of that which get into people’s mind, like children will go to school in the dark. Countries change their time zones often, so although UTC will deviate, the time that we follow doesn’t have to. That’s set by law; it can be whatever the countries want. It’s my opinion that no matter what the ITU decides, if they don’t decide to get rid of leap seconds now, they will decide to get rid of it in another 20 to 30 years after the problems get more pronounced.”
Guest
- Demetrios Matsakis, chief scientist for Time Services at the U.S. Naval Observatory.
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