Goodbye Teardrops
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Ask anyone to imagine a falling raindrop, and likely they will picture a teardrop shape. But, although poetry and song are filled with descriptions of raindrops as sky tears, that image, we shall see, is wrong.

Water: Mid-Air Observatory Photojournal

While raindrops hitting a surface may roll off like tears flowing down the cheek, they actually form a flattened-sphere shape as they fall.

A century ago, German physicist Philipp Lenard, used a vertical wind tunnel to determine the true shape of falling water drops. He found raindrops begin as spherical drops. But as their descent accelerated, the air flowing past pushed against the lower drop surface until the spherical shape was distorted, looking more like a hamburger bun with its flattened base and rounded top.

Even the bun shape, however, is idealized. If we could isolate a large drop in a rainstorm and follow it from formation until final splashdown, we would never see a teardrop. Instead, we would see the drop's shape deform under changing aerodynamic forces in the turbulent air stream and collisions with other drops.

First, as the falling water mass reacts to the turbulent, changing aerodynamic forces around it, the bun-shaped drop takes on a variety of generally spherical shapes, at times distorting to a sagging dumbbell shape, before returning to its original shape or splitting into smaller drops.

As raindrops fall, there are many collisions among them. When drops bounce off one another, the collisions cause distortions in their shapes, vibrating like falling globs of jello. Other collisions cause drops to combine into large drops that oscillate in shape between spherical and dumbbell shapes.

So shed a tear of farewell for the tear-shaped raindrop. Thanks to contributing writer, Keith Heidorn