光的理论实际上是弹性介质振动的理论。

What you actually pay for something is at least twice the listed price because of the energy， time， money needed to set it up， learn， maintain， repair， and dispose of at the end. Not all prices appear on labels. Actual costs are 2x listed prices.

正义意味着关心自己的事情，而不是干预别人的事务。