You placed a sphere of radius r in a room of which maintains at Tsur. The sphere is somehow hanging in the center of the room. Air in the room is completely evacuated. Initial temperature of the sphere is at Ti which is higher than Tsur. Determine the maximum radius of the sphere so that the temperature of the sphere is not a function of location. Define yourself for the necessary parameters: comment) although there should be a temperature discontinuity between the sphere and the walls of the room, you just neglect this and assume that there is no temperature discontinuity.