**How did the Earth's core slow down in 2009 and why did we find out about it in 2023?** [Multidecadal variation of the Earth’s inner-core rotation](https://www.nature.com/articles/s41561-022-01112-z) Scientists have found that the Earth's inner core, which is the center part of the Earth, has slowed down its rotation. They discovered this by analyzing earthquakes that happened between the 1990s and today. They noticed that over the past decade, the inner core has not been rotating as much as it used to. This slowing down is part of a pattern that happens every 7 decades, where the inner core turns back relative to the outer layer of the Earth. This pattern affects other things like the length of a day and the Earth's magnetic field. This means that there are interactions happening between the different layers of the Earth, from the inner core to the surface, that could be caused by things like the Earth's gravity and the transfer of movement from the inner core and outer layer. @mr27.near?