Have you ever looked at water dripping from a tap and wondeed why they are perfectly spherical and not any other shape?
Water drops, or, for that matter, the drops of any other liquid, are spherical in shape due to a phenomenon called surface tension. In a liquid this acts on the surface of a freely falling drop to minimise its area.
Compared to other objects, such as an ellipsoid (an egg-shaped object), the ratio between the surface area and the volume is minimum in case of a sphere.
Surface tension, in simpler terms, is the tendency of the surface of a liquid to behave like a stretched membrane. This results from the attraction between the molecules in the liquid.
Molecules at the surface of any liquid, unlike the ones in the interior, do not experience a uniform attractive force. The ones at the intersurface of liquid and air are attracted more towards the bulk of the liquid. As a consequence, all liquid surfaces, in the absence of any other external force, tend to contract. Since a sphere has got the minimum surface-to-volume ratio, falling liquid drops are always spherical in shape.
In the case of bubbles also, it is surface tension that plays a major role in determining their shape. This seemingly simple yet profound phenomenon serves as a reminder of nature’s ability to find balance and harmony in the microscopic world.