The planet's solid iron inner core has stopped spinning faster than the surface, a new study suggests.
A study carried out at Peking University has found that the centre of the planet is slowing down its rotation. We speak to Dr Jessica Irving, a seismologist and senior lecturer based at the University of Bristol's School of Earth Sciences about what this means. Advertisement What does the inside of the Earth look like? The crust of the Earth is made of rock. Then we've got this huge expanse that we call the mantle. That's solid rock-like material, but it's under high pressure and high temperature so it's different to the rocks that you would find if you wandered out into a park. Beyond the bottom of the mantle we get into the deepest regions of the Earth, to the core. There we leave the rocks behind and enter a big ball made of iron in the centre. That ended up there because iron is heavier than rock. We're talking about a huge ball that's about half of Earth's radius made of metal. But we can also split that core into two more distinct chunks. We have the outer core, which is made of molten metal. Then in the middle, we've got the solid inner core, which has a radius about a fifth of the Earth's. How do we study changes to the Earth's core? We have a variety of different techniques to make what we call indirect observations. No hole that has been dug that's going to help out. The deepest ever hole was a bit over 12 kilometres deep. To get down to the inner core, we need to go down thousands and thousands of kilometres and we certainly have no samples. Seismologists look at a record of an earthquake wave which has gone right through the rocky mantle - the liquid outer core, into the inner core - and all the way back out and to the far side of the planet. Then they try and look for another earthquake that happened as close as possible and was detected by exactly the same seismometer. What…