Earth completes its fastest ever rotation – what does this mean?

On June 29, the Earth experienced its shortest day on record. It completed one rotation in 1.59 milliseconds under its usual 24 hours.

It may seem insignificant, but the potential impacts have been called ‘devastating’.

Typically, Earth’s average rotation decreases sightly over time. This has led to 27 ‘leap seconds’ – an extra second to keep our clocks in sync with solar time – to be added to the Coordinated Universal Time (UTC). We last added a leap second on New Year’s Eve 2016. Midnight struck twice worldwide as clocks paused for one second, allowing the Earth’s rotation to catch up with us.

Contrastingly, the speeding up of Earth’s rotation could require a ‘negative leap second’. This means that for the first time in history, timekeepers may need to speed up clocks worldwide and effectively remove time. The potential effects of this could impact some key components of modern life.

If this continues, our satellite communication and navigation systems could be compromised as they rely heavily on time’s consistency with the usual positions of the sun, moon and stars. Not only this, but various IT systems and software that depend on schedulers and timers could be seriously affected. Such systems could experience large-scale outages if their internal clocks were to be moved backwards. Experts have called the potential consequences ‘devastating’.

Scientists have speculated on the possible causes of this record-breaking rotation. One explanation could be the Chandler Wobble – movement in Earth’s axis of rotation that causes latitude to vary. Dr. Leonid Zotov, of the Sternberg Astronomical Institute, noted that, “The normal wobble amplitude is about four meters at Earth’s surface, but from 2017 to 2020 it disappeared.” Without this wobble, Earth is completing its rotation faster than usual.

Another potential cause could be climate change. Rising sea levels are impacting the Earth’s distribution of mass, bringing it closer to its rotation axis and speeding up its rate of rotation. This process has been compared to an ice skater pulling their arms in while spinning to increase speed.

Processes taking places in the planet’s inner molten core could also be to blame. Experts discovered that the Earth’s core is in fact rotating slightly faster than the planet itself. Over the past 100 years, this has resulted in the core gaining a quarter-turn on the rest of the planet.

While the exact cause is undetermined, it may well be a combination of all possibilities.

Following this record-breaking rotation, only time will tell the measures experts may take to keep our clocks in check.