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Reality-based commentary on politics.

We Should Oppose Abolition of the Leap Second

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Cross-posted from Letters Blogatory

Readers, I am going to subject you today to an editorial on a topic that periodically gets me worked up even though it has nothing to do with private international law: the proposed abolition of the leap second. I’m sorry to say that the United States is the main proponent of the change. Here is the story.

What is a Leap Second?

Today, the world’s time standard is coordinated universal time, or UTC. Why UTC instead of CUT? Well, in French, it’s temps universel coordonné, which could be abbreviated TUC. UTC, which stands for neither the French name for the standard nor the English name, was apparently a compromise between the Francophone world and the Anglophone world.

The Royal Observatory, Greenwich

The Royal Observatory, Greenwich. Credit: Shizhao

The old way of keeping time, known as Universal Time, or UT (the English won that round!), was based on astronomical observations of the sun. We observed the length of the mean solar day, and then divided that day into hours, minutes, and seconds. So the second was in a sense defined to be 1/86,400 of the solar day and depended on the period of the earth’s rotation about its axis. To be sure, the solar day is not the only natural way to measure time: we could also measure time by the length of the year—by the period of the Earth’s revolution around the Sun rather than its rotation about its own axis. Astronomers and other scientists made use of this so-called ephemeris time because they knew that the length of the solar day was not perfectly uniform: the earth’s rotation is slowing down over time. And they had a system of converting UT to ephemeris time, or in other words, a system of tying the natural length of the day to the natural length of the year.

US Naval Observatory atomic clock

The master atomic clock ensemble at the US Naval Observatory, Washington, D.C. Credit: Coenen.

But with the development of highly regular atomic clocks in the 1950s, we began to think of the second not as a subdivision of a fundamental unit of time like a day or a year, but as the fundamental unit of time in its own right, and to define the second with reference to the number of “ticks” of the atomic clock. And since the period of the Earth’s rotation was not perfectly uniform, it became necessary to insert occasional “leap seconds” into UTC to keep the official time in line with the natural period of the day. (The more familiar leap year serves a similar function, keeping the official time in line with the natural period of the year). There have been 25 leap seconds since 1972, and thus UTC is now 25 seconds behind the time scale that relies only on the ticking of the atomic clock without reference to days and years, called International Atomic Time, or TAI (the French must have won that round).

Why Do Some People Want to Get Rid of the Leap Second?

GPS Satellite In Orbit

Artistic Impression of a GPS Satellite In Orbit. Credit: NASA

Now that computers rely on highly precise time synchronization throughout the Internet and where airplanes, ships, and cars rely on highly precise measurements of time to determine their position using GPS, there is a hue and cry each time a leap second is declared (the next leap second will be in June 2015). A group called the Civil GPS Interface Committee has declared the leap second a hazard to navigation. IT people seem to be unable to ensure that their computers can properly account for leap seconds, leading to computer glitches and crashes. And so the United States is proposing that the leap second be abolished. The effect of this proposal would be to remove the link in principle between days and years on the one hand and the inexorable ticking of the atomic clock on the other. To be sure, because leap seconds are so rare, in practice time as measured by atomic clocks will be more or less the same as time measured by the sun or the stars for many, many years to come.

Why Should You Care?

Days and years are meaningful for human beings. We live our lives in days and years. In my view we should take the meaningful units of measurement as the fundamental units of measurement, and then subdivide as appropriate. The SI definition of the second, useful in atomic clocks, “the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom,” is meaningless for human beings. It might just as well be 9,192,631,771 or 9,192,631,772, or 10,000,000,000 periods. And even granted that we can measure the absolute interval of time between two events with such precision, it’s meaningless, on a human scale, to do so. I see no reason why we should move from a standard of time that is meaningful to a standard of time that is meaningless, especially because over time the result will be that the natural, meaningful definition of time we all use everyday will become progressively more “wrong.”

Well, what about high-speed computers and other technology that require a very high degree of precision and synchronization? It’s a technical problem that the people who have a vested interest in ultra-precise time should bear the cost of fixing. And while I’m no expert, it seems to me there is a pretty easy answer: let the airlines and the Internet companies use TAI. In other words, let them simply stop adjusting for for leap seconds. Let the atomic clocks become progressively more wrong.

It seems to me we have our priorities backwards when we worry about how to keep our everyday natural time in sync with our atomic clocks instead of vice versa!

Further Reading

I had thought about quoting at length Hannah Arendt’s prologue to The Human Condition, a great book, which at the dawn of the space age expressed similar thoughts about cutting the necessary link between humankind and the earth (she didn’t have the measurement of time in mind). But instead of quoting it, I will just say: go read it! It’s a great book.

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Comments

  1. Nobody should be expending any attention to the leap-second mote so long as the DST beam is firmly lodged in their eye. Let’s start with abolishing that completely useless and enormously disruptive thing before worrying about whether satellite timekeeping can be adjusted by a second once in a while.

    • I’m with you, Kirth, on the ridiculousness of DST. But conceptually the leap second is much worse. DST happens each spring and then un-happens each fall. So there’s no net change and certainly no “untethering” from the sun. Elimination of the leap second would be a conceptual change in the measurement of civil time that would unmoor the official time from nature. Just sayin’.

      • So there’s no net change and certainly no “untethering” from the sun.

        The disruption to sleep cycles is a change, twice yearly, and is a bigger threat to health than the leap second which is, essentially, a correction to a rounding error. Your contention is, if I read it correctly, that the correction is largely artificial and not strictly necessary to sync the lived time with actual time.

        Both of these implementations, DST and leap second, are disruptive. DST is disruptive to humans. Leap seconds are disruptive to computers. There is little that can be done to cure the disruption to humans, we have to endure it. It’s not fatal, but it is deleterious… and, I think, un-necessarily so. There is a cure for the leap second: good programming. Computers are wholly deterministic: they are so predictable that the sole job they have any real difficulty with is creating randomness…. All else they can handle. If some computer can’t deal with a leap second then it is the fault of the programmer and not the existence of the leap second. I will go so far as to say that, should we fail to program computers and systems that can handle the disruption of a leap second then we’re all going to die in the frozen vastness of space when and if we do un-tether from this world.

    • What’s so bad about DST? It has been nice to get home during daylight this week.

      • Sunset today is 6:46. That would be 5:46 without DST. Perhaps you’d like to console those who left for work before the sun rose at 7AM. Or those who survived driving into the rising sun for 2 weeks, and now get to do it again for another 2 weeks. THAT is one of the things that’s so bad about DST. Then there’s the increase in traffic accidents, and heart attacks.

        I was talking to my mom about DST on Sunday. She says it was started in WWI and was supposed to benefit farmers. This was a mystery to her. She lived on a farm at the time, and her father’s workday didn’t have anything to do with what the clock said. Later, it was supposed to be good for school children, so they wouldn’t have to go to school in the dark. Apparently, going home in the dark is better. Now I guess it’s so you can go home in daylight a couple of weeks early.

        • I like being able to wake up in relative light in the winter AND extending daylight time in the evening in the summer. I never have understood why you’re so hostile to this.

        • This week has been like….well..I don’t have words. REALLY REALLY EFFING NICE.

          It’s still dark out but I can look out the window at around the time my brain checks out and still see sunshine. it’s a win.

        • There is an association with a higher risk of heart attack in spring, and a corresponding negative association in fall. So, even if you accept the premise of causation, which isn’t proven, then the whole thing is a wash.

          Also, invest in sunglasses and slow down.

          Even in December, sunset isn’t until 4:15PM. What school doesn’t get out until 4:00PM?

          This sounds a bit like pet-peeve contrarian-ness.

      • You’d think IT professionals would have figured this out by now, but they haven’t.

        Servers that use local, rather than UTC, time and that have time-based processes to run (backups, mailers, maintenance windows, etc) have to jump through hoops twice a year to handle DST. Peer-to-peer systems, with geographically distributed participants, are even worse.

        Lay people generally don’t realize that DST ripples across North America, from east to west. A common tactic is to avoid scheduling ANY jobs between 1:00a and 2:00a, but this leads to surprisingly complex issues when participants are distributed across the country. In the fall, there’s an added complication … any given server sees the same “time” twice, once before and once after the fall set-back.

        I don’t have a strong opinion, one way or the other. I, too, enjoy the daylight at the end of the day. Still, we all pay a distinct price for all this — beyond the often-discussed energy consequences.

        • We can have the end-of-day light without the destructive semiannual clock dance. Just declare DST as Standard time, and do away with the Fall-back change. It’s all arbitrary, anyway. China has one time zone, across a country as wide as ours. I’m not advocating that, just using it to illustrate the arbitrary nature of time decrees. Settling on one standard year-round would also end the hiccups produced by Arizona, which doesn’t recognize DST (except for the Navajo Reservation, which does).

          • …by the Carter Administration, and earlier, during World War Two as an energy saving measure.

            Acting with promptness difficult to fathom today, our elected leaders then enacted year-around Daylight Savings Time, dropped the speed limit to 55, and established government price controls. And, oh so fleetingly, we downsized what we drove. All gone.

          • Noon should be when the sun is at it’s highest point in the sky at which point a sundial would cast essentially no shadow. My understanding is that standard time does that whereas daylight time is artificially off by an hour.

            • You might find this ted talk enjoyable.

              Noon is whenever a community decides it should be. The relationship between when a clock in the community reads “12:00p” and the position of the sun in the sky above that clock is, in fact, arbitrary.

              Within a timezone, the sun is at its highest point in the sky an hour earlier on the eastern boundary than on the western boundary. The sun does not jump across the sky as a person travels across the time zone boundary and changes their clock.

              “Standard Time” and time zones were created when railroad travel made it possible to travel far enough fast enough to make local time unmanageable. Prior to automatic signals, railroads had to use synchronized clocks and train orders to prevent trains from colliding. There were far too many local jurisdictions, each with their own local time, to make this possible. Hence the introduction of “standard” time and with it, time zones. Called “railroad time” for decades, standard time was introduced by the railroads on November 18, 1883 at 12:00p. “Standard time” was enacted, as a matter of law, by the federal government on March 19, 1918. DST came after that.

              The way that we measure time most certainly is arbitrary.

              • it has to be a little standardized, but otherwise the concept holds. I of course understand the sun doesn’t jump, but there’s a reason there are 24 main time zones.

                • Why aren’t there 48 time zones? That would reduce the distance that the Sun is from its zenith at 12PM in edge cases. Why 24 hours, for that matter? Why not 20, or 10?

                • The 24-hour time system has its origins in the Egyptian astronomical system of decans

                  Decans continued to be used throughout the Renaissance in astrology and in magic, but modern astrologers almost entirely ignore them.

                  Nobody has used the thing that’s the basis for our time system for hundreds of years, but we still have 24-hour days and 24 time zones because of it. It is about as arbitrary as it’s possible to be.

                • When my children were in grade school and learning about arithmetic and the metric, we played a game that we all loved.

                  I had them invent their own “metric calendar”. The goal was to invent a calendar that is to time what the metric system is to distance. We agreed that we needed a “day”, and “year”, and that there are 365 days in a year (we ignored leap years).

                  The kids loved it, they asked astonishingly insightful questions, and I still have the carefully-drawn calendars in a keepsakes box.

                • At least a true lunar month is. I don’t know off hand where a 12-month cycle came from as a year consists of 13 lunar months. I’m not aware of a reason for a 7-day week that doesn’t originate in Genesis.

                • The seven-day week as such was first decreed by King Sargon I of Akkad around 2300 BCE. Due to his vast conquests, the Akkadian culture and language spread, and through the Akkadian-speaking Babylonian Empire it reached down all the way to the present day. It seems likely that the Hebrew week is based on the Babylonian tradition, although going through certain adaptations. From Judaism the seven-day week was adopted by Christianity and with time became the universal norm.

                  Also arbitrary, of course.

                  For instance, the Chinese Han Dynasty (from 206 BCE) used five-day and ten-day cycles.

                • I just happened on this page of the very useful timeanddate.com website. It includes a world map of timezones, which illustrates how completely not-based-on-solar-position the time zones are. For example, San Jose, Costa Rica is east of Indianapolis, but is two hours later. Places on the map that are diagonally shaded are in zones that are shifted 30 minutes from their neighbors. The map looks like electoral districts in Texas after the Republicans got through gerrymandering them (or, of course, MA when the Dems were done),

  2. Love a good theological conversation. Are we humans going to be so arrogant as to deny our status as a part of creation? I think this is how Frankenstein (and a bunch of other stories) get started.

  3. I still don’t see why I should care about this. Either you set your clocks by hand, in which case you probably don’t get it down to the exact second, or you have them automatically set themselves from the internet or cellular network. This is just not something that anyone needs to think much about.

    Re DST, I like it. Even though I have a pretty flexible work schedule, I still have to deal with fixed commuter rail schedules, so I definitely appreciate the extra light at the end of the day when I have the time to take my dogs for a long walk in the park.

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