Raindrops Are Not Teardrop-Shaped

The classic image of a teardrop-shaped raindrop is a persistent myth, likely born from watching water drip slowly from a surface. In the atmosphere, physics tells a different story. For very small raindrops, less than a millimeter in diameter, the dominant force is surface tension. This is the cohesive force that causes water molecules to pull inward on each other, minimizing their surface area into the most compact, energy-efficient shape possible: a near-perfect sphere.

As a raindrop grows and falls, its speed increases, and it begins to encounter significant air resistance. The pressure of the air pushing up against the bottom of the falling drop is greater than the pressure on the top. This flattens the bottom of the drop while the top remains curved, transforming the sphere into a shape more accurately described as an oblate spheroid, or the top half of a hamburger bun. This effect becomes noticeable once a drop reaches about two millimeters in diameter.

If a drop grows even larger, typically beyond four or five millimeters, it becomes unstable. The air pressure pushing up from below creates a deep indentation, making the drop look more like a parachute or a jellyfish. This unstable shape cannot hold together and is quickly torn apart by the aerodynamic forces, breaking up into a collection of smaller, more stable spherical drops to begin the cycle again.