27 Mar Time Out Of Mind
I sometimes love to redefine stuff–concepts, ideas, certainly stereotypes–stuff that we were certain we had already settled and were positive about.
It may feel confusing, but it can also lead to fresh thinking. At the very least, it shakes us up and re-sorts us. So today, we’re onto ways of keeping time. No metronomes necessary.
Approximately every four years, an extra day gets linked on to the end of February, a time-keeping convention known as the leap year. The practice was established by Julius Caesar more than 2000 years ago and modified in the 16th century by Pope Gregory XIII, bequeathing to us the Julian and Gregorian calendars. The extra day is a way of aligning the calendar year of 365 days with how long it actually takes earth to make a trip around the sun, which is nearly one quarter of a day longer. The added day ensures the seasons stay put instead of shifting around the year as the mismatch lengthens. So now it turns out that–to blow your brain a bit–we humans are also trying to impose order on the small end of the scale: the second. Traditionally, that unit was defined in astronomical terms, as one 86,400th of the mean solar day (the time it takes earth to rotate once on its axis). Got that?
Then, in 1967, the world’s metrologists began measuring time with atomic clocks. The official length of the basic unit, the second, was fixed at 9,192,631,770 vibrations of an atom of cesium 133. And 86,400 such seconds compose one day. But Earth’s rotation slows slightly from year to year, and the astronomical second, like the astronomical day, has gradually grown longer than the atomic one. To compensate, starting in 1972, metrologists began occasionally inserting an extra second—a leap second–at the end of an atomic day: whenever atomic time is a full second ahead, it stops for a second to allow the earth to catch up. Ten leap seconds were added to the atomic time scale in 1972, and 27 more since: no small task. Are you still with me?
Moreover, earth’s rotation is somewhat erratic, so the leap second is both irregular and unpredictable. A half-century ago those qualities made inserting the leap second challenging, but today the attempt is a nightmare, because precise timing is now integral to our highly computerized infrastructure.
“What was before just a way of measuring the flow of time is today essential for transportation, location, defense, finance, and space competition,” according to Felicitas Arias, former director of the Time Department of the International Bureau of Weights and Measures, known as the BIPM from its French name. The process of squaring those time scales has become so messy that the world’s time experts made a bold decision: to abandon the leap second by 2035. In twelve years, then, civilization will embrace atomic time, and the difference between atomic time and earth time will go unspecified until timekeepers come up with a better plan for reconciling the two. (Hmm. That sounds a tad problematic and, uh, slipshod to me.) This will sever the time-keeping of atoms from the time-keeping of the heavens, probably for generations to come. But the change won’t be discernible for us, since it will take a thousand years for atomic time to diverge as much as an hour from earth time.
But that second is a huge amount in Internet technology. Cell phone transmissions, power grids, computer networks, all are synchronized to miniscule fractions of a second. High-frequency traders in financial markets execute orders in thousands or even billionths of a second. By international law, data packages for these transcriptions must be time stamped to that fine level of precision, recorded, and made traceable back to Coordinated Universal Time (UTC), the universally agreed upon standard managed by timekeepers at the BIPM. Hello? You there?
Each additional leap second introduces confusion: that some digital networks won’t adopt the change correctly, or know precisely what time it is with regard to other systems, or fail to synchronize properly. The leap second is a drop of potential chaos in a recipe that demands precision. For that reason, discarding it had wide support from nations across the world, including the United States, but the result of the vote was high drama, and involved more than two decades of study, negotiation, and diplomatic compromise. Russia, for instance, tried to delay a shift away from the leap second because that would require extensive alterations to its GLONASS satellite system. The United Kingdom historically is tethered to the astronomical standard, enshrined in Greenwich Mean Time–although the UK finally did became a firm supporter of ditching the leap second. What’s more, the fate of the leap second also affects Coordinated Universal Time, the international standard for time-keeping that the leap second had heretofore been slowly undermining. Coordinated Universal Time, or UTC, is constructed from readings made by atomic clocks at national laboratories around the world, who send the measurements to the BIPM. The assembly process takes time. Once a month the Bureau publishes the perfect time in the form of a newsletter that tells each national clock how much it diverges from the international standard. That, at least, is pretty clear, yes?
Coordinated Universal Time is the world’s official time scale and will remain so, even without the leap second. Global time zones are described in reference to it. And the second is the most important in the constellation of standard measurements overseen by the BIPM, alongside the meter (length), the kilogram (mass), kelvin (temperature), candela (intensity of light), ampere (electric current), and mole (amount of substance). The idea of UTC, normalized a century and a half ago by national signatories to an international treaty called the Meter Convention, is that each unit of measurement should be identical everywhere in the world: 1 meter in Spain is precisely 1 meter in Singapore. In addition, the second is tethered to a time scale, or flow of seconds. A key tenet of modern life is that not only must the unit of time be identical no matter where it is measured, so must the flow of seconds of which that one is a part. But the leap second was putting that tenet at risk. Removing it from the UTC will make the Standard Time scale. There! All clear now?
Oops, oh, um, wait. You see, none of this addresses the time scale most commonly used in place of UTC: the US government’s global positioning satellite system, or GPS. Each satellite in that network carries atomic clocks that provide time data, longitude, latitude, and altitude. GPS users include cell phone and data networks and can determine the time of day to within 100 billionth of a second with information freely, widely available. But! It is neither funneled through the BIPM nor adjusted for leap seconds. However, if telecommunication networks make GPS rather than UTC their official time, the implications are enormous: using it rather than UTC would mean the time would no longer be overseen by an organization that must abide by international agreements. The increasing use of signals from GPS satellites effectively mean that the US military controls the primary source of international time signals with almost no oversight nationally or internationally. (Is this where we play the Twilight Zone theme, or flashback to the X Files?)
And that’s not all. Clocks aboard satellites are inconsistent across systems. Galileo, the European system, is 18 seconds ahead of UTC, but in sync with GPS. The Chinese system BEIDOU is 4 seconds ahead. And so forth. Even computing systems that currently insert the leaps do so in different ways. Google blurs the extra second across a whole day while Meta, Alibaba, and Microsoft each add the extra second in their own ways. It’s a massive muddle. And a further alarm looms: the leap second has previously been necessary since atomic time runs faster than earth time, but that’s changing. Earth’s rotation rate began speeding up around the time the leap second was invented. So at some point earth time will catch up to atomic time, and by about 2030, if the trend persists, overtake atomic time by about a second–so metrologists will have to insert a negative leap second to keep the time scales in sync. Many metrologists fear digital disaster. This could make Y2K (remember Y2K?) look like the ABCs.
So. Now you can be as thoroughly confused as I am, although we can each cling to the little shard of information we could manage to glean from all this. And look: I valiantly resisted going into “the arrow of time” or quantum theories about reversing that!
But listen: we can’t even get the US House of Representatives to make sensible Daylight Saving Time permanent, although the US Senate already voted for that. In 2018, the European Union parliament voted to keep clocks the same all year round, but they’ve been stumped as to how to do so, or which settings to choose. Timekeepers in the future will continue to try to reconcile atomic time with celestial–perhaps with a leap minute, which will be called for in about a century–or eventually a leap hour, or something not yet conceivable. One thing we’re certain about: time rules everything. (Or does it?)
[This blog will be on hiatus next week.]