Scientists have long thought Earth's inner core is like a huge solid metal ball. But an experiment revealed it may be a lot softer — more like butter, a lead scientist said. It could help ...

A solid sphere (such as a marble) (It does not need to be the same size as the hollow sphere.) Cardboard box or stack of textbooks Flat, rigid material to use as a ramp, such as a piece of foam ...

Researchers studying decades of earthquake data say they have found the first evidence that, in addition to spinning backward, Earth’s inner core in changing shape.