Goodbye to the leap second; Scientists have adopted a new way to set global time

A new system called "leap clock" allows the rotation of the Earth and the Universal Coordinated Clock to be separated by up to a full hour.

On Thursday, October 15, an international group of scientists, diplomats, and chronologists voted to eliminate the leap second; The mechanism that until today kept Coordinated Universal Time (UTC) in sync with Earth's Rotational Time (UT1) and kept their difference within one second.

According to Zomit, the length of a night in the UTC scale is almost equal to its length based on UT1; But since our planet's rotation is irregular, the two time scales are not exactly the same. For this reason, we add a leap second to Universal Time every few years to prevent the difference between UTC and UT1 from growing too large.

But the leap second will soon give way to the leap hour; A change that is going to be implemented very late and will increase the maximum allowed difference between the time based on the rotation of the Earth and the Universal Coordinated Time to one hour (or 3,600 seconds).

Shortly before the recent vote, Noel Dimarck, senior scientist at the French National Center for Scientific Research (CNRS) and head of the Time and Frequency Advisory Committee at the International Bureau of Weights and Measures (BIPM), said that after 30 years of discussion, we are finally ready to vote on keeping or removing the bag second. The vote was held at the General Conference of Weights and Measures (CGPM) in Versailles, France.

Coordinated Universal Time is the world's standard time scale. It is the time reference scale for computers, telephones, ships, airplanes, satellites, and almost all other instruments. Also, navigation systems like Global Positioning System (GPS) work based on it. UTC is calculated from the weighted average of time recorded by atomic clocks around the world and published by the International Bureau of Weights and Measures.

Shortly after UTC was first established in 1960, scientists noticed that the Earth's rotation was slowly slowing; As a result, this rotation does not keep pace with the counting of seconds based on atomic clocks. At the request of astronomers and other experts, the first leap second was added to UTC in 1972 to bring the time standard back into sync with the Earth's rotation. Since then, 27 leap seconds have been added to this time scale.

However, in the mid-2010s, the Earth's rotation began to accelerate. Scientists predicted that we would soon need a negative leap second; This may happen even from 2029. Engineers say that a negative leap second could be an event similar to "a small problem on the scale of the 2000 bug"; Because it would suddenly move time around the world back by one second and might disrupt our digital infrastructure.

Scientists predict that leap clocks will not be needed for more than 1,000 years

"Avoiding the need for negative leap seconds is one of the most important factors in expanding the permissible difference between UTC and UT1," said Nick Stamatakos, chief of the Earth Orientation Division at the US Naval Observatory, which manages the nation's GPS network.

Since 2022, scientists, government officials, telecommunications experts and other experts have been working hard to find a practical solution to the leap second problem.

The International Bureau of Weights and Measures, which is the official authority of the UTC, holds a General Conference on Weights and Measures every four years to discuss various issues with the participation of member countries. On Thursday evening, officials at this year's conference voted to eliminate the leap second and convert UTC to a continuous time scale. The resolution was approved by the majority vote and was set to be implemented on May 20, 2027, equal to the World Metrology Day.

According to the new agreement, instead of using leap seconds, everyone has agreed that the difference between UTC and UT1 will increase more than before. If this difference becomes large enough, we will eventually add a leap hour. Although in the past a leap second was added to universal time every few years, scientists predict that leap hours will not be needed for more than 1,000 years. This decision effectively ends efforts to keep Universal Time in sync with the Earth's rotation.

Most of us won't notice the leap second being removed, and the transition to continuous time will make it easier for digital infrastructure; Because the risk of software errors or service interruption due to discontinuity caused by leap seconds is significantly reduced. However, this change means further distancing of human civilization from the oldest way of measuring time: looking at the sky.