Earth is suddenly spinning faster than usual, but why?
In the 1960’s, scientists began measuring the planet’s rotation with high-precision atomic clocks. And on June 29 this year, Earth racked up an unusual record: its shortest day since then, rotating 1.59 milliseconds less than 24 hours.
July 26 neared the newly-set record, at 1.50 milliseconds shorter than usual. So, why is the Earth spinning faster? Scientists are not completely certain, but they have a few possible explanations.
Some experts believe the melting and refreezing of ice caps could be contributing to the irregular speed, according to the New York Post.
Earthquakes can also make the days shorter. The 2004 earthquake that unleashed a tsunami in the Indian Ocean shifted enough rock to shorten the length of the day by nearly three microseconds.
Also known as the Chandler variation of latitude, the “Chandler Wobble” is a natural shifting of the Earth’s axis due to the planet not being perfectly spherical, and could be linked to the spinning speeds.
On the other hand, stronger winds in ‘El Niño’ years can slow down the planet’s spin, extending the day by a fraction of a millisecond, according to NASA. The name 'El Niño' is used to describe the warming of sea surface temperature that occurs every few years.
Basically anything that moves mass towards the centre of the Earth will speed up the planet’s rotation, much as a spinning ice skater speeds up when they pull in their arms. Geological activity that pushes mass outwards from the centre will have the opposite effect and slow down the spin.
Over the longer term, the geological timescales that compress the rise and fall of the dinosaurs into the blink of an eye, the Earth is actually spinning more slowly than it used to.
Wind the clock back 1.4 billion years and a day would pass in less than 19 hours. On average, then, Earth days are getting longer rather than shorter, by about one 74,000th of a second each year.
The moon is mostly to blame for the effect: the gravitational tug slightly distorts the planet, producing tidal friction that steadily slows the Earth’s rotation.
Image: Anderson Rian/Unsplash
To keep clocks in line with the planet’s spin, the International Telecommunication Union, a United Nations body, has taken to adding occasional leap seconds in June or December, most recently in 2016.
The first leap second was added in 1972. The next opportunity is in December 2022, although with Earth spinning so fast of late, it is unlikely to be needed.
Earth’s quickening rotation has consequences because atomic clocks, which are used in GPS satellites, don’t take into account the Earth’s changing rotation.
If Earth spins faster, then it gets to the same position a little earlier. A half-a-millisecond equates to 10-inches or 26 centimetres at the equator. In short, GPS satellites would become useless.
There are also potentially confusing consequences for smartphones, computers and communications systems, which synchronize with Network Time Protocol (NTP) servers.
To solve all this, if the trend for shorter days carries on for long, it could lead to calls for the first “negative leap second”. Instead of adding a second to clocks, civil time would skip a second to keep up with the faster-spinning planet.