廣義相對論(二) 初步的理解

• General principle of relativity: All bodies of reference are equivalent for the description of natural phenomena (formulation of the general laws of nature), whatever may be their state of motion.
  
• The gravitational mass of a body is equal to its inertial mass.
  

因此，把重力場等效為加速度，研究加速度系統，就可推出重力場的物理現象，真是夠聰明的。不過問題來了，怎麼用數學清楚描述這些事？