If it feels like the days are longer than ever, it might not just be your boring job that’s to blame.
A new study has shown that changes in the Earth’s inner core could increase the length of days.
According to a team from the University of Southern California, the Earth’s dense metallic core is now moving back relative to the Earth’s surface.
By looking at earthquake data, they found that the inner core began to slow down around 2010 and is now moving backward, subtly affecting Earth’s rotation in space.
Don’t expect to enjoy more hours in the day just yet, though, as the researchers say the change may be very hard to notice.
A new study has shown that changes in the Earth’s inner core could increase the length of days
If it feels like the days are longer than ever, it might not just be your boring job that’s to blame (stock image)
The Earth consists of four main layers: the crust, mantle, outer core and inner core.
At the center of the planet, 3,000 miles below our feet, is the inner core: a superheated ball of solid iron and nickel, about the size of the moon.
Because the surrounding outer core is completely liquid, this dense metal sphere can spin freely under the pull of Earth’s magnetic field and the gravitational influence of its outer layers.
For years, many scientists believed that the inner core rotated faster than the Earth’s surface.
However, Professor John Vidale, an earth scientist at the University of Southern California, says the core has now slowed down and is starting to move backwards.
“The dance of the inner core may be even more alive than we know yet,” he said.
Without any way to directly observe the Earth’s inner core, the researchers relied on data collected from seismic events.
Professor Vidale and his co-authors focused in particular on events called repeating earthquakes – seismic events that occur at the same location and produce identical patterns in recordings called seismograms.
In addition to 121 natural events recorded around the South Sandwich Islands, the researchers also used human events such as the Soviet twin nuclear tests between 1971 and 1974.
As seismic events send shock waves through the Earth, the state and location of each of the layers will subtly change the shape of the wave that scientists record.
When the waveforms of repeating waves match, it reveals times when the inner core is in exactly the same position relative to the Earth’s outer layers.
Researchers discovered series of seismograms in which a repeating earthquake would occur, change, and match again a few years later.
For example, the data showed that a March 2003 earthquake was slightly different than a 2009 earthquake at the same location, but identical to the 2020 earthquake.
The Earth consists of four main layers: the crust, mantle, outer core and inner core. At the center of the planet, 3,000 miles below our feet, is the inner core: a superheated ball of solid iron and nickel, about the size of the moon.
Researchers looked at 121 events called “repeating earthquakes” that stretch from the South Sandwich Islands (shown with a red star) to North America
What that shows is that the inner core moved relative to the surface between 2003 and 2009, only to return to the same position in 2020.
This means that the inner core must have been rotating forward relative to the surface until sometime in 2010, when it began to slow down and move backward.
Professor Vidale said: ‘When I first saw the seismograms indicating this change I was amazed.
‘But when we found another twenty observations that signaled the same pattern, the result was inevitable. The inner core had slowed down for the first time in many decades.”
This slowdown could be caused by the churning of the liquid iron core that generates Earth’s magnetic field, but also by gravitational pulls from unusually dense regions in the mantle.
Although the effects this will have are almost impossible to predict, Professor Vidale says it could change the length of the day by a very small amount.
He says: ‘It is very difficult to notice, on the order of a thousandth of a second, almost lost in the noise of the swirling oceans and atmosphere.’