Not flat shapes like circles and squares, but solid shapes like cubes and cones ... GIRL 1: Now the next shape is a sphere. Try to make yourself into a sphere – a big ball!

Shape changes in the core could hold clues ... Of all Earth’s layers, the inner core is the most remote and mysterious. This solid sphere of iron and nickel is about 70% the size of the moon ...

[DaveMakesStuff] demonstrates a great technique for 3D printing a sphere; a troublesome shape for filament-based ... at a higher temperature to ensure solid bonding between each layer.

The Earth's inner core, long considered a solid and stable sphere, may be quite different ... causing changes in shape. These disturbances could also explain the gradual slowdown in the rotation ...