Thunder is the sound caused by lightning. When lightning occurs, it heats the surrounding air to an extremely high temperature, causing the air to expand rapidly. This rapid expansion¹ creates a shock wave, which we hear as thunder. The reason thunder rumbles² and lasts for several seconds is because the sound waves travel different distances and reflect off objects like clouds and the ground.

雷声是由闪电引起的。当闪电发生时，它会使周围的空气迅速加热到极高的温度，导致空气急剧膨胀。这种快速膨胀产生冲击波，我们听到的就是雷声。雷声之所以隆隆作响并持续几秒钟，是因为声波传播的距离不同，并且会在云层和地面等物体上反射。

总结来说，雷声是闪电加热空气并产生冲击波的结果。