Earth is spinning few milliseconds faster: Should you be worried?
What's the story
Earth's rotation speed has increased this summer, resulting in slightly shorter days. The International Earth Rotation and Reference Systems Service (IERS) confirmed July 10 was the shortest day of the year so far, at 1.36 milliseconds less than 24 hours. More exceptionally short days are expected on July 22 and August 5, currently predicted to be 1.34 and 1.25 milliseconds shorter than a full day, respectively.
Rotation dynamics
Why Earth's rotation speed varies
A day is defined as the time taken by Earth to complete one full rotation on its axis, which is usually 24 hours or 86,400 seconds. However, this process isn't uniform and can be affected by various factors like the Moon's gravitational pull, seasonal atmospheric changes, and Earth's liquid core. These variations are usually in milliseconds and don't affect our daily lives significantly. However, these minute variations in Earth's rotation can have long-term effects on computers, satellites, and telecommunications systems.
Technological implications
Atomic clocks were introduced in 1955 to monitor minute variations
To monitor these tiny discrepancies, atomic clocks were introduced in 1955. These devices measure time with extreme precision by counting the oscillations of atoms in a vacuum chamber. The resulting time, known as Coordinated Universal Time (UTC), is based on around 450 atomic clocks and serves as the global standard for timekeeping. Last year, on July 5, Earth recorded its shortest day since the advent of atomic clocks in 1955, at 1.66 milliseconds less than 24 hours.
Spin acceleration
Earth has been spinning faster since 1972
Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography, noted that Earth has been spinning faster since 1972. However, there are fluctuations similar to stock market trends. In 1972, after decades of slow rotation, IERS added a "leap second" to UTC due to Earth's spin lagging behind atomic time. Since then, 27 leap seconds have been added but their frequency has slowed down as Earth speeds up. Notably, no new leap seconds have been added since 2016.
Time adjustment
Abolishment of leap seconds by 2035
Historically, positive leap seconds corrected slower rotation. However, a faster spin could lead to a negative leap second. In 2022, the General Conference on Weights and Measures (CGPM) voted to abolish leap seconds by 2035. However, if Earth continues to spin faster for several more years, Agnew suggests one second might need to be removed from UTC. He says there's never been a negative leap second but the probability of having one between now and 2035 is about 40%.