时间反演对称性是经典电动力学与非相对论性量子力学的一种基本对称性,它描述的是时间反演后某些基本物理过程依然成立.例如,刚性光滑小球之间的碰撞过程在时间反演后仍然满足牛顿运动定律,然而微观尺度上摩擦力却导致了时间反演对称性破缺,即小球运动减慢与时间反演后加快不相符.推广到电磁场,一方面,真空中的电磁波传播就类似于无摩擦情况下的小球碰撞,满足时间反演不变性;另一方面,与电磁波相互作用的介质可以吸收电磁波,类似于摩擦力的作用,从而破坏了时间反演对称性.简单地说,吸收 Time inversion symmetry is a basic symmetry between classical electrodynamics and nonrelativistic quantum mechanics, which describes some basic physical processes after time inversion. For example, the collision process between rigid and smooth small balls After time inversion, Newton’s law of motion is still satisfied, however, the friction force at micro scale causes the symmetry breaking of time inversion, that is, the slowing down of small ball does not accord with the acceleration after time inversion. The extension to electromagnetic field, on the one hand, In the electromagnetic wave propagation is similar to the frictionless ball collision to meet the time invariance; on the other hand, the interaction with the electromagnetic wave medium can absorb electromagnetic waves, similar to the role of friction, thus undermining the time inversion Symmetry. Simply put, absorbed