When the weather is clear, you can see stars shining at night. What caused this?

Most of the stars you see at night are stars, and some are stars in the solar system, such as Venus, Mercury and Mars. The luminous principle of stars is similar to that of the sun. Most of them release energy in the process of hydrogen merging into helium nuclei, and some of them release energy in the process of helium fusion. Just because they are far away from us, they look like gentle little stars. In fact, they are much bigger than the sun. Planets look brighter because they reflect sunlight. However, they only occupy the light near us and look brighter than the stars.

Blankets of nitrogen, oxygen and other gases in the atmosphere not only make our world warm and pleasant, but also protect us from harmful ultraviolet radiation, not to mention evaporated space debris. By the way, if there is no oxygen in the atmosphere, animals including us can't even survive in this world. The difference between temperature and density will inevitably lead to the constant fluctuation of air flow in the atmosphere. This kind of airflow fluctuation is usually called wind. When light from a distant star enters the earth's atmosphere, it must pass through the atmosphere with continuous violent motion, which is usually called turbulence in astronomical terminology.

The stars themselves do not twinkle. It seems to be flashing, because when we look at the stars, our eyes pass through the air covering the earth. When the light of a star shines on the earth, it will pass through the unstable hot and cold air layer. Different air layers refract starlight in different forms. In this way, it seems that the brightness of the stars is changing and the stars are flashing.

The twinkling of stars is actually the influence of the atmosphere on light, which changes the starlight we receive with our naked eyes. We should know that the stars themselves do not twinkle. Stars in outer space will shine out in a balanced and stable way. If you are outside the earth's atmosphere, you will find that when there is no atmospheric disturbance, the stars observed by the naked eye will not flicker. Only when starlight enters the earth's atmosphere will the timeline bend and spread, thus changing the starlight received by human eyes. On the earth, the stars seem to wink at us, because the earth's atmosphere contains changes in wind, temperature difference and density.