If someone asked you to draw a rain shower, you’d probably illustrate a puffy cloud with a handful of tear-shaped drops falling to the ground. That is how rain is popularly depicted, after all.
But if you look at rain through the eyes of an atmospheric scientist, you’d see something completely different. Each raindrop actually resembles something like the top of a burger bun. The reason has to do with the fact that a falling raindrop is in motion and therefore has forces acting on it.
When a raindrop first forms, it’s microscopic. Small enough and light enough to stay suspended high up in the clouds. At this point, it’s a perfect sphere. As more water vapor particles glom onto the raindrop, it grows, eventually becoming heavy enough to succumb to the force of gravity.
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As the drop grows, it starts falling faster. This is where air resistance comes into play. The bottom of the raindrop gets flattened out as it falls through the surrounding air. Meanwhile, the force of surface tension, or the strength of the bonds holding water molecules together, keeps the top of the raindrop more spherical.
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Eventually, raindrops grow too large and are forced to split apart into multiple new drops. The growth process starts all over until the droplets finally splash to the ground.
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