Why is the Sun, Moon and Earth spherical?

To learn about this theory, learners of Grade 2 were asked to hold a hula hoop with one hand and imagine they’re holding onto gravity. They were asked to change or move in another direction without leaving the hula hoop, but they couldn’t because gravity held them in the original shape which is a round. This was a wonderful way to learn the fundamental scientific rules that we may usually overlook in our daily life.