14 DAY TRIAL // A new video posted to the NASA Global Precipitation Measurement mission website explains in simple terms that water drops are not shaped like teardrops, a popular misconception that is reinforced to the general public every day. The clip shows the actual shape of water drops, and explains how they come to look like hamburger buns.
The most important thing to keep in mind about raindrops is that they are not rounded at the bottom and pointy at the top, but rather flat at the bottom, and round at the top. This appearance is produced when the surface tension of water enters into play as rain starts.
When raindrops first start falling – after condensing around smoke and dust particles in the upper atmosphere – they are less than 1 millimeter in diameter, and round. As they collide with, and engulf, other droplets, they can grow to be 2 to 3 millimeters (1/8th on an inch) across, meaning that air resistance begins to flatten their bottom.
If they grow beyond 4.5 millimeters (3/16th of an inch) in diameter, air pressure is high enough to make them look like parachutes. Usually, raindrops of this size break apart into two separate droplets, and the entire process starts anew. See the video above for more details.