Reckoning / Shape / Hollow sphere (shell)
Solid · Spheres
Hollow sphere (shell)
A ball with a concentric ball removed, like a float or a tennis ball.
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Dimensions
Results
volume V
Formulas
Outer ball minus inner ball. Topologically it is not a ball: it has a sealed cavity, and its boundary is two separate spheres.
Checked: the V formula agrees with a Monte Carlo measurement of the shape itself, made from its geometric definition, every time the site is built.
Topology lens
A solid with a sealed cavity. Its boundary is two separate spheres, so the Euler characteristic of the surface is 2 + 2 = 4. More on the lens.