When Einstein first applied his general theory of relativity to the universe, he made a dramatic simplifying assumption: the universe, on average, was homogeneous (it had no big lumps) and isotropic (it looked the same in all directions).

• 当爱因斯坦首度将广义相对论应用在宇宙学上时，他做了一项重大而精简的假设：宇宙在大?围是均匀（而不是一团一团的）且各向同性（各个方向看起来都一样）的。