It’s official: the leap second will be retired (in a decade)

The time has come – or will come, in 2035 – to abandon the leap second.

So voted the member states of the international treaty governing science and measurement standards, at a meeting in Versailles, France, on Friday. The near-unanimous vote on what was known as Resolution D was greeted with relief and jubilation by metrologists around the world, some of whom have been calling for a solution to the leap second problem for decades.

“Incredible,” wrote Patrizia Tavella, director of the time department at the International Bureau of Weights and Measures, known as BIPM by its French name and based outside Paris, in a WhatsApp message shortly after the vote. “Over 20 years of discussions and now an excellent agreement.” She added that she was “moved to tears”.

The United States was a strong supporter of the resolution. “It feels like a historic day,” said Elizabeth Donley, head of the time and frequency division at the National Institute of Standards and Technology, or NIST, in Boulder, Colorado. “And I wish I had been there. There are probably a lot of celebrations that are done in style.

The leap second has caused problems since its inception 50 years ago. It was designed as a means of aligning the international atomic time scale, in use since 1967 and derived from the vibration of cesium atoms, with the slightly slower time that the Earth maintains as it rotates. Indeed, each time atomic time is one second ahead, it stops one second to allow the Earth to catch up. Ten leap seconds were inserted into the atomic time scale when the fudge was unveiled in 1972. Twenty-seven more have since been added.

Those extra seconds were difficult to squeeze in in 1972; today, the technical problems are thorny. On the one hand, it is difficult to predict exactly when the next leap second will be needed, so computer networks cannot prepare for orderly and regular insertions. Different networks have developed their own uncoordinated methods to incorporate the extra second.

Additionally, modern global computing systems have become more tightly interwoven and more dependent on hyper-precise timing, sometimes to billionths of a second. Adding an extra second increases the risk that these systems, which are responsible for telecommunications networks, power transmission, financial transactions and other vital businesses, will hang or fail to synchronize.

As a result, unofficial time systems slowly began to replace official world international time, Coordinated Universal Time, or UTC. The elimination of the leap second is seen as a way to preserve observance of UTC by making it a continuous time scale rather than an interrupted episodic scale.

“The bigger issue is the preservation of the concept that time is an international quantity,” said NIST physicist Judah Levine. He called Versailles’ decision “an incredible step forward”.

Russia voted against the resolution; Belarus abstained. Russia has long sought to delay abandoning the leap second because its global navigation satellite system GLONASS incorporates the extra seconds, unlike other systems such as GPS, which is operated by the United States. With Russia’s concerns in mind, the leap second is not expected to be abandoned until 2035, although it could happen sooner.

Resolution D asks that UTC not be interrupted by leap seconds from 2035 to at least 2135 and that metrologists eventually figure out how to reconcile the atomic and astronomical time scales with fewer headaches. The international standard of time would be cut off from time as the heavens said for generations to come.

But joining those two timescales was imperative, said the Reverend Pavel Gabor, an astrophysicist and vice director of the Vatican Observatory Research Group in Tucson, Arizona. He said atomic timing was just one example of how the world was becoming incomprehensible to the average person, and that scientists had a responsibility to help people feel in control of their lives.

“I think the sensitivity to this distrust of elites, distrust of experts, distrust of science and institutions, that’s something that’s a very real problem in the world today,” he said. he declared. “And let’s not contribute to it.”

Steps remain in the elimination of the leap second. Although the BIPM is responsible for universal time, the International Telecommunication Union, or ITU, is responsible for its transmission. The ITU World Radiocommunication Conference in Dubai, United Arab Emirates, will also vote on the issue next year. Felicitas Arias, former director of the time department at the BIPM and now a guest astronomer at the Paris Observatory, said negotiations between the two organizations have convinced her that the ITU will support the Versailles vote.

“Now we see closer the moment to have continuous time,” she said, applauding Friday’s vote. “And that’s something we’ve been dreaming about for a very, very long time.”

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