Orbium (heavenly spheres) is a fundamental concept of Greek mathematical astronomy of which Copernicus was the orthodox successor.

• “天球”是希腊数理天文学的基本概念 ,哥白尼正是这一数理天文传统的正宗传人。 强调是“天球”不是“天体” ,是为了恢复科学史的实情