Why is the sky blue?

The sky is blue because of the scattering of sunlight. The reason why the sky is blue is that sunlight is made up of seven kinds of light. Of the seven kinds of light, green, cyan, blue and purple have higher frequencies, and the light with higher frequencies is most easily scattered by air molecules and dust in the air, so when sunlight passes through the atmosphere, most of the four kinds of light are scattered.

The proportion of purple in the solar spectrum itself is relatively small, most of the purple light and ultraviolet light are absorbed by the ozone layer, and the rest is mainly cyan, so the sky will appear beautiful blue.

The mystery of the sky

People can observe meteorological or astronomical phenomena in the sky, so as to know the change of weather, the passage of time or their position. You can know the time of day at sunrise and sunset, and the moon's profit and loss for a month at night. The big dipper can indicate the north. The thickness and shape of clouds can judge whether it will rain or not.

You can enjoy many beautiful phenomena in the sky, such as rainbow, aurora and meteor shower. Birds can fly in the sky. Due to the increasing use of fossil fuels such as oil, especially fuels such as coal that will release sulfur dioxide after burning, the visibility of the sky has gradually decreased since 1973, except in Europe.

Refer to the above? Baidu Encyclopedia-Sky