Sphere-world
The idea of a sphere-world was constructed by French mathematician Henri Poincaré who, while pursuing his argument for conventionalism (see philosophy of space and time), offered a thought experiment about a sphere with strange properties. == The concept == Poincaré asks us to imagine a sphere of radius R. The temperature of the sphere decreases from its maximum at the center to absolute zero at its extremity such that a body’s temperature at a distance r from the center is proportional to R 2 − r 2 {\displaystyle R^{2}-r^{2}} .