WHY ONLY STARS BLINK AND NOT PLANETS?

The stars seem to twinkle, because we see the stars through the ocean of air, the atmosphere. The twinkling is caused by differences in temperature in the air. Some layers of air are hotter than others, and one layer is always swirling and moving through another. These different layers of air bend the star light in different ways, and at different angles. It is this passing through layers of air of different temperature that makes the light of the stars unsteady. The stars near the horizon seem to twinkle much more than those high in the sky. This is because the light of these stars has to travel a longer path through a thicker layer of atmosphere, and thus has more chance to become disturb. Sometimes the stars twinkle much more than they do at other times. This is true because at sometimes the atmosphere is not so still as it is at other times, or because there is not such a variation of temperature within its different layers. Planets do not twinkle, ordinarily, but seem to shine with a steady, unwavering light. Even through large telescopes, the biggest stars appear simply as tiny points of light, while the planets show very definite discs and surfaces. Hence, more rays come to us from the surface of a planet than from the surface of a star. The light from the planets does not waver as much as that from the stars the wavering of one ray of light is counteracted by the wavering of another ray in another direction. If one could climb up above the atmosphere surrounding the earth and then look at the stars, he would see them shining with a clear and steady light, with no suspicion of twinkling.