Why does a small mercury drop assume a spherical shape?

A mercury drop is. spherical in shape. Why?

Small liquid drops assume sherical shape because

Why does mercury not cling to glass?

Why does mercury drop its level in a capillary tube?

Why are rain drops spherical?

Why does AlCl_3 fume in air?

Why does the level of mercury fall in a capillary?

What is the gravitational force on a body inside a spherical shell? Why is it so?

What is Huygen's principle? Show that at a larage distace from the source, a small portion of the spherical wave can be approximated by a plane wave.