Tom Hunt
The name for our planet's shape is an 'oblate spheroid', which is like a sphere squashed slightly in one direction (like if you press down on a soccer ball on the floor; Smarties are also oblate...
yes a pentagon is a rigid shape* * * * *I am afraid that it is not.
A 2 dimensional shape such as a circle is NOT a solid shape, while a sphere is.
Many 3d shapes have a corner.