Hi, my friends and I are curious to know about the day and night cycle. Don’t you want to know why we have the day and night cycle? Come, join us on our trip and explore this wonder of the universe.

嘿，我和我的朋友们都很好奇想知道昼夜更替。难道你不想知道为什么我们会有昼夜更替吗？来吧，和我们一起来探索这个神奇的宇宙吧。

Objective:

·           We will learn that day and night cycle is a natural phenomenon that takes place on the earth.

·           我们将会知道昼夜更替是地球上发生的一种自然想象。

Planets in the solar system are in constant motion and they revolve around the sun. All these planets, including the earth, also rotate on their own respective axis. This rotation results in day and night on the earth. Check this out, the world time zone map shows that it is day time on some continents, while it is night-time on the others. How does this happen? Come! Let us look at the position of the earth with reference to the sun to understand this phenomenon. The sun is in a fixed position in the solar system. The earth, as you know, constantly rotates on its own axis which is an imaginary line that runs from the North Pole to the South Pole through the centre of the earth. This rotation is from west to east and takes 24 hours to complete. Due to this rotation and positioning of the earth and the sun, it so happens that only one part of the earth can face the sun at any given time. Hence, the part that faces the sun has day, while it is night on the other side of earth that is facing away from the sun. Thus, the rotation of the earth changes day into night and night into day again. However, that part of the earth which has night-time is illuminated by the moon. But the moon does not make its own light. Just as sunlight strikes the surface of the earth, it does that of the moon as well. The moon reflects this light on to the earth during night. This explains the day and night cycle. It’s time to get back home.

太阳系中的行星是在不断运动的，它们围绕着太阳旋转。所有这些行星，包括地球在内，同时也都围绕着它们各自的轴旋转。这种自转的结果是导致地球出现白天和黑夜。来看看这个，世界时区地图显示当一些大陆是白天时，而其他大陆则是夜晚。这是如何发生的呢？快来！让我们根据太阳查看地球的位置来理解这种现象。太阳在太阳系中的位置是固定的。地球，正如你所知道的，它不断地围绕着它自己的轴旋转，这个轴是一条假想线，它通过地心并连接北极和南极。这种自转是自西向东的，完成自转所需要的时间是24小时。由于地球和太阳的这种旋转和定位，在任何特定的时间内地球碰巧只有一部分是对着太阳的。因此，对着太阳的那一部分是白天，而在背对太阳的地球另一端则是黑夜。这样，地球的自转让白天变为黑夜，并再次让黑夜变为白天。尽管如此，地球有黑夜的那一部分由月球来照亮。但是月球本身是不会发光的。就像太阳光照射到地球的表面一样，月球也是接受太阳光的照射。在夜晚，月球把该太阳光反射到地球上。这就解释了昼夜更替。是时候该回家了。