Letters Blogatory: Still Against Abolishing The Leap Second

Artemis I launch

In her prologue to The Human Condition, written at the dawn of the space age, Hannah Arendt wrote:

The earth is the very quintessence of the human condition, and earthly nature, for all we know, may be unique in the universe in providing human beings with a habitant in which they can move and breathe without effort and without artifice. The human artifice of the world separates human existence from all mere animal environment, but life itself is outside this artificial world, and through life man remains related to all other living organisms. For some time now, a great many scientific endeavors have been directed toward making life also “artificial,” toward cutting the last tie through which even man belongs among the children of nature. It is the same desire to escape from imprisonment to the earth that is manifest in the attempt to create life in the test tube … and the wish to escape the human condition, I suspect, also underlies he hope to extend man’s life-span far beyond the hundred-year limit.

This future man, whom the scientists tell us they will produce in no more than a hundred years, seems to be possessed by a rebellion against human existence as it has been given, a free gift from nowhere (secularly speaking), which he wishes to exchange, as it were, for something he has made himself. There is no reason to doubt our abilities to accomplish such an exchange, just as there is no reason to doubt our present ability to destroy all organic life on earth. The question is only whether we wish to use our new scientific and technical knowledge in this direction, and this question cannot be decided by scientific means; it is a political question of the first order and therefore can hardly be left to the decision of professional scientists or professional politicians.

I was thinking of this when I read about the latest attempt to abolish the leap second in the New York Times. When the second was first defined, it was defined with reference to the day. The day was divided into twenty-four hours, the hour into sixty minutes, and the minute into sixty second. Thus a second was 1/86,400th of a day. For a long time our clocks were not as good at keeping accurate time as the earth itself, which rotates on its axis, well, once per day. But as early clocks were replaced by better and better technology, we eventually learned to keep time with extreme precision. Greater precision than the earth, because the length of the day changes by a very small amount as the earth’s rotation slows down or speeds up.

In order to keep the ticking of the clock in sync with the rising and setting of the sun, we add (or in principle, subtract) a second every few years. Coordinated Universal Time, or UTC, the basis for civil time, is defined as International Atomic Time (TAI), offset by the number of leap seconds added to the clock since the inception of the system. But adding leap seconds turns out to cause all kinds of problems for networked computers. The professionals haven’t found a perfect solution. Hence their proposal. They want simply to abolish the leap second. That is, they want to let UTC drift over time from the day measured by the rising and setting of the sun, in order to make life easier for network engineers.

You might ask, reflecting what Arendt had to say about hubris and nemesis, who dares to cut yet another link between us and the earth. But if you did ask that, as I did back in 2015 when I last wrote about leap second, actual experts in the science of time might tell you, as they told me offline, that I didn’t know what I was talking about and to stay in my lane. Maybe they were right! But what take away from the Times argument is that the real problem isn’t technical, but political and bureaucratic. Whose lane are we in? It seems that we could just synchronize networked computers to the time signals emitted by GPS satellites, which don’t use leap seconds and which, at least according to the article, would provide a good technical solution to the problem. But the scientists in charge of the measurement of time regard GPS as an unacceptable solution, because it takes the measurement of time out of the treaty-based bureaucracy that they run. To me, it seems crazy to divorce time from the rhythms of the earth not to solve a technical problem, but to protect some bureaucratic turf.

A last word on Arendt. When we think about a future for humankind on other planets today, our mental picture is probably sunnier than it was in Arendt’s day. We have discovered lots of extrasolar planets, and we suspect that even other places in our own solar system may not always have been as hostile to life as they are today. Who knows, maybe one day our engineering will let us make other planets habitable. Anyway, there are few sights that are more stirring, or a greater sort of national pride and pride in humankind, than the launch of a really big rocket, like yesterday’s Artemis I launch, the first step on NASA’s mission to have long-term human habitation on the Moon and, eventually, Mars.

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