这是一篇简易的科普读物，向我们讲述了生命与阳光，太阳与地球之间的关系。
Nobody can live without the sun. The sun gives us light and heat， and light and heat give us life. Without the sun， we should be in complete darkness. With no light and heat at all， the earth would be very cold and would be all snow and ice. Then all plants and animals and men would die. Life would stop and there would be a cold， dark and dead world.
We cannot live without light and heat. Yet， if the sun is always shinning up- on us， we cannot bear it either， because we shall certainly be burnt to death. The earth will be too hot to live on.
We need the night to bring us rest and sleep. We do not have the sun at night， because our earth is always spinning round the sun and therefore only one side of the earth sees the sun at one time. When we see the sun on the side of the earth， it is day to us. When we cannot see the sun， it is night.