James Stewart

If the car alternates between travelling slower and faster than the bus, then there'll be times when it's ahead of the bus, there'll be times when it's behind, and times when it's back aligned with the bus again.

So the study examined P waves produced from 121 earthquakes that took place between 1991 and 2023 in the South Sandwich Islands.

The waves passed through the Earth's inner core and were detected by seismometers in Alaska and Canada.

Using this methodology, they confirmed the findings of the previous year, that the changes in the inner core's rotation speed follow a 70-year cycle and, more than that, according to their calculations, it's just about due to speed up again.

As for what causes this change, scientists aren't yet certain.

Possibly the magnetic field of the liquid outer core could drag on the solid iron within, speeding it up or slowing it down.

While gravity from dense regions in the mantle could pull on variations in the inner core affecting its rotation.

But what does that mean for us?

Do we need to worry about this?

Well, remember how I said earlier that the inner core is like the boiler room of our planet?

Well, it turns out that changes in its behavior do seem to correlate with other phenomena on the surface.

The authors of the 2023 study noticed that 70-year oscillation coincides with fluctuations in the length of a day and changes in the magnetic field.

And beyond that, they even linked them to changes in global mean temperature and sea level.

But before you're too alarmed, we're talking about tiny changes here.

A thousandth of a second here.

A fraction of a degree there.

Certainly not enough to explain global warming.

The long story short is it's early days.

Scientists are continuing to study the inner core and its impacts on the world above.

And with every passing year yielding more and more seismic data ripe for analysis, new insights are only a matter of time.