The world’s time lords – otherwise known as the International Bureau of Weights and Measures (BIPM) – have voted to do away with the leap second by 2035. Allowing time to simply run its course without intermittent interference , the organization hopes to end decades of meaningless disruption to global technology systems.
The leap second was first introduced in 1972 as a means of balancing the gap between the astronomical and atomic timekeeping scales. While both systems agree that a 24-hour day contains exactly 86,400 seconds, the different ways in which they define the length of a second result in an infinitesimally small, yet extremely significant shift in time.
More precisely, the astronomical second is determined by dividing the time required for the Earth to complete one rotation by 86,400, while the atomic second is exactly 9,192,631,770 vibrations of a cesium-133 atom. And although these two units are almost identical, the gradual slowing of the Earth’s rotation means that the duration of the astronomical second increases very slightly over time.
Atomic clocks thus find themselves slightly ahead of astronomical time, and the leap second was devised as a means of realigning the two systems. Essentially, every time atomic time advances a second, it pauses a second so Earth’s rotation can catch up.
Occurring once every few years, these tiny adjustments are imperceptible to the average biological Earthling, but cause major headaches for our technological neighbors. For example, computer systems that rely on exact timekeeping sometimes crash when the leap second disrupts their calculations.
Telecommunications infrastructure, satellite navigation and all manner of software struggle to cope with interruptions in the flow of time, while the fact that leap seconds are not periodic compounds the situation by making it difficult to predict the when they will occur. The first ten leap seconds were introduced when the workaround was first devised half a century ago, and another 27 ticks and tocks have been inserted into the atomic time scale over the years since followed.
By keeping the two timelines synchronized, leap seconds allow the BIPM to maintain Coordinated Universal Time (UTC), the official timekeeping system by which all clocks are set. However, due to problems caused by leap seconds, some technology programs have abandoned UTC and instead use their own measurements. Perhaps the most notable example is GPS, which keeps time by a different method that doesn’t include episodic adjustments.
The BIPM’s decision to abandon the leap second was made in part to encourage greater adherence to UTC by making it a more transparent time scale. Patrizia Tavella, who heads the BIPM’s time department, told AFP the change would result in “a continuous flow of seconds without the discontinuities currently caused by irregular leap seconds”.
Of course, this means that the difference between atomic time and astronomical time may grow to more than a second, and so some sort of realignment will be needed at a later date. The extent to which the two timelines will be allowed to diverge and the method by which they will be brought back into sync once leap seconds are a thing of the past have yet to be decided.
Negotiations to find a solution should take place by 2035, when the new hourly regime will come into effect.