Question

Why rainwater falling is spherical in shape

Answer 1

Surface tension comes into action at liquid air interface.
Raindrops naturally attain a spherical form to decrease surface area.
Sphere, having the least surface area: volume ratio, is the most stable shape in terms of potential energy.
Water, like all liquids possess a property known as surface tension. Now, whenever liquids are found in a mass, the outermost layer of molecules tend to be closer together, as compared to the molecules in the rest of the substance. This phenomenon or property is called surface tension, which causes the surface of the substance to cover the least possible area. Now, when raindrops fall from the sky, they are suspended in the air. So the outermost molecules stick together to cover the least possible area. And the least possible surface area of a volume is that of a sphere. That is why rain drops are spherical when they fall from the sky. You may observe this phenomenon even when you scatter some drops of water on a surface. Most of the masses will appear to form shapes that cover minimum area.