Earth is suddenly spinning faster than usual, but why?

June 29, 2022: the shortest day since the 1960’s
Three days earlier, also shorter than usual
Climate change
Earthquakes
The “Chandler Wobble”
Strong winds and warm oceans
Speed up / Slow down
So, is the world speeding up?
1.4 billion years ago, a day would be less than 19 hours
Tidal friction slows the Earth’s rotation
Adding seconds on the clock to keep up with the planet’s spin
With Earth spinning fast lately, leap seconds won’t be needed
How does Earth’s rotational speed affects us?
GPS satellites would become useless
Smartphones, computers and communication systems
“Negative leap second”
June 29, 2022: the shortest day since the 1960’s

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.

Three days earlier, also shorter than usual

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.

Climate change

Some experts believe the melting and refreezing of ice caps could be contributing to the irregular speed, according to the New York Post.

Earthquakes

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.

The “Chandler Wobble”

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.

Image: Chuttersnap/Unsplash

Strong winds and warm oceans

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.

Speed up / Slow down

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.

So, is the world speeding up?

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.

1.4 billion years ago, a day would be less than 19 hours

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.

Tidal friction slows the Earth’s rotation

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

Adding seconds on the clock to keep up with the planet’s spin

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.

With Earth spinning fast lately, leap seconds won’t be needed

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.

How does Earth’s rotational speed affects us?

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.

GPS satellites would become useless

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.

Smartphones, computers and communication systems

There are also potentially confusing consequences for smartphones, computers and communications systems, which synchronize with Network Time Protocol (NTP) servers. 

“Negative leap second”

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.

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