aether

The ancient Greeks believed that the stars were embedded in a sphere of aether.

古希腊人认为星辰嵌在以太的球体中。

In some philosophical systems, aether is considered the fifth element, pure and unchanging.

在某些哲学体系中，以太被视为第五元素，纯净且不变。

The idea of aether as a medium for light waves was later disproven by Einstein.

以太作为光波介质的想法后来被爱因斯坦推翻。