A hollow Earth would be less than 0.4% of its current mass.

一个中空的地球将小于其当前质量的 0. 4%。

But after eight billion years the sun will have finally become a White Dwarf star equal to fifty-four percent of its current mass.

但 80 亿年后，太阳最终会变成一颗白矮星，其质量相当于目前太阳质量的 54%。