Spherical shell apparatus
From AMS Glossary
spherical shell apparatus
An experimental apparatus intended to represent, for modeling purposes, the geometric and dynamic effects of the earth's sphericity.
It is composed of two concentric spheres (usually glass) of different radii. The space between them is filled with some working fluid and the entire shell is rotated. The inner sphere represents the surface of the earth, and the outer sphere is an artificial upper limit of the model atmosphere.