Question

Why do the stars twinkle but not the planets

Answer 1

Stars twinkle because they have their own light i.e. they are luminous object (the objects which  have their own light eg. fire flies, sun, stars) .

The stars are very far away from earth thus they appear as points to us and when the light which has high frequency comes to us they appear to twinkle.

But on the other hand planets do not have their own light so are non -luminous objects (the objects which do not have their own light eg. moon and other planets ,etc.) .

Since the light from the sun strikes on the planet and gets reflected on the earth we can at least see them .