Don’t forget the extra second!
Attention: tonight, at midnight on December 31, 2016, you are going to have to adjust your clocks. We don’t want anyone missing a flight, or arriving at a meeting too early.
The earth, as even the most reactionary religious people now admit, is a sphere that revolves around the sun, and rotates on its axis, as it has done for billions of years. The revolution around the sun takes 365¼ days, which is why every four years we have to add a day to the normally 365-day year. The earth has rotated on a slightly tilted axis, just think of it, over a trillion times. On its surface we are travelling at a speed of 1,674 kilometres an hour through surrounding space.
Currently it takes 24 hours for the earth to complete a single rotation, and we call this period a day. Well, more or less 24 hours. Geological and climatic events — earthquakes, the melting of glaciers, can influence the rate of rotation. A science journalist colleague of mine tried to convince me that the trillions of tons of bio mass that are lifted to the top of trees and shrubs, and shed back to the ground each year, also have to be considered — just as an ice skater stretching out or pulling in her arms changes the torque on her body, causing her to spin slower or faster. I don’t quite buy it.
In any case, currently the rotation is slowing down. Due to tidal friction it takes the earth on average slightly longer (0–2 milliseconds) than 24x60x60=86,400 seconds to rotate on its axis. If we stuck to exactly 86,400 for each earth day our atomic clocks would, over the centuries, register the sun rising earlier and earlier. To avoid that, we have to periodically add time to our clock. We do not do this regularly, like adding the 29th of February every four years to compensate for the extra time the earth takes per revolution around the sun. The time we add is a “leap second”, and 26 of them have been inserted since 1972, when atomic clocks were introduced and the precise difference was recognized.
The leap second is usually introduced on June 30 or December 31 of the year, and it is done with the unusual time display shown here:
Normally the display progresses from 23:59:59 to 00:00:00, but when a leap second is added the official UTC clock has the extra second inserted. Somebody actually stayed up the last time and did a screen grab.
So: be sure to reset your clocks and watches tonight, so you will not waste time by arriving a second early for meetings. Of course if you have radio controlled devices, like the ones that permeate my home, then they adjust themselves automatically and make sure you are in sync.
Now for the story that inevitably accompanies such tedious technical articles. My father, Alois Friedel, was a watchmaker (and a herpetologist, a hunter, a competent amateur astronomer, a music aficionado, a polyglot, and a number of other things). Actually, he rejected the term watchmaker and called himself a “horologist,” an expert in the measurement of time. In the middle of the previous century he set up stations in ports around Asia where ships could synchronize their clocks, in order to ensure that they would navigate correctly.
This was in the direct tradition of John Harrison, English carpenter and clock-maker who in the 18th century invented the marine chronometer. If you haven’t read Dava Sobels book Longitude, get it immediately — preferably the illustrated version. It is one of the finest scientific books ever written. The film is great as well.
Well, my horologist father developed ever more advanced ship chronometers, and serviced the existing ones. The captains of ships in port would bring in their chronometers, and get in return a fully refurbished one, set to the exact time. My father’s company would then take apart the one brought in and soak all moving parts in alcohol. This was to remove from the bearings all residual oil, which over the time thickens and slows the clock down. I assisted in this process as a child, and I still have a bottle of the (very expensive) porpoise jaw oil that was used when the chronometer was put together again:
Alois Friedel (whose original German name was Friedl) was constantly developing ever more accurate chronometers, and on the side very accurate timepieces for household use. Here’s one he built when I was seven:
The entire escapement of this timepiece, in the middle on the top, rotates 360°, to compensate for all external influences. The clock, which is covered with a glass dome, took him a year to design and build, and to set running to an accuracy of a few seconds a month. When I recently took it to a watchmaker in Hamburg, Germany, he said, after cleaning and refurbishing it: “It is really an extraordinary piece of work, made by a true master.”
Luckily my father did not live long enough to see the day when watches that are far more accurate than anything he ever built could be bought for a dollar or two. But he left in his son a deep fascination for timekeepers…
…and when in the mid 1970s the first quartz watches appeared, my wife bought me one. It was quite expensive: 149 Marks, which would be like 300 Euros today. But it was an appropriate Christmas present for a watch and time fanatic.
As chance would have it, a week after I got the watch they had a leap second (isn’t it amazing how I find back to the original subject?). It was announced on television and was featured prominently in the news, since this was something new. I duly set my watch one second back, and the next day was pleased to see that it synchronized perfectly with the TV news clock.
But then we switched to “DDR Deutscher Fernsehfunk”, the Communist East German TV channel. And when I checked their clock against my watch it was two seconds off.
I puzzled for a while over this and then, realizing what had happened, called a Hamburg newspaper and told them: the TV people in East Germany had switched their clocks the wrong way! They had set the clock forward instead of backward by one second.
The newspaper was quite intrigued and asked me to write a piece on it for them, which I duly did. It was one of the first stories I ever got published, and it appeared the next day, before the DDR TV people had noticed anything. For my effort I was paid exactly 150 Marks so that we ended up with a one Mark profit on the watch. Not a bad deal.