太阳是一个圆圆的发光火球。早晨,太阳从东方升起;傍晚,太阳在西边落下。每当这时,我们就会发现它的形状不是圆形,而是一个椭圆。这是为什么呢? 原来,这是由于大气对太阳光的折射造成的。光的折射是指光线从一种物质斜射到另一种物质中时,在两种物质的界面上,光的传播方向发生改变的现象。这样的现象很多,插入水中的筷子就像折了似的,也是这个道理。 The sun is a round glowing fireball. In the morning, the sun rises from the east; in the evening, the sun sets in the west. At this time, we will find that its shape is not a circle but an ellipse. Why is this? Originally, this was caused by the atmospheric refraction of sunlight. The refraction of light refers to the phenomenon in which the direction of light propagation changes at the interface between two substances when light ray strikes from one substance to another. There are many such phenomena. The chopsticks inserted into the water are like folds. This is also the reason.