Explain why the planets do not twinkle?

Explanation

Since stars are very far from the earth, they can be considered as point-sources of light. The refractive index of the earth.s atmosphere keeps changing continuously [due to wind] and it also decreases with increasing altitude [ due to decrease in density of air]. Hence, the starlight entering the earth.s atmosphere undergoes continuous refraction by the atmosphere causing changes in intensity of starlight entering our eyes. Thus, stars appear to be twinkling. On the other hand, planets closer to the earth behave as extended light sources formed of a series of point-sources. Changes in intensity from these large numbers of point-sources average to zero and hence, no twinkling is observed.