Spherical shell

In geometry, a spherical shell is a generalization of an annulus to three dimensions. It is the region between two concentric spheres of differing radii. In geometry, a spherical shell is a generalization of an annulus to three dimensions. It is the region between two concentric spheres of differing radii. The volume of a spherical shell is the difference between the enclosed volume of the outer sphere and the enclosed volume of the inner sphere: where r is the radius of the inner sphere and R is the radius of the outer sphere. An approximation for the volume of a thin spherical shell is the surface area of the inner sphere multiplied by the thickness t of the shell: when t is very small compared to r ( t ≪ r {displaystyle tll r} ). A Dyson sphere encloses a fictitious spherical shell around a star, as first described by author Olaf Stapledon.