What image pops into your mind when you think of a raindrop? Is it the tear-shaped droplet that you see in cartoons, or even see dripping from a faucet? Contrary to popular belief, raindrops are shaped like hamburger buns. Most droplets are flat on the bottom and domed at the top. In this article, we will discuss why we think of them as tear-shaped and how raindrops acquire this shape along with a few other forms.
In art, water is typically teardrop-shaped, it is what makes it easily recognizable and memorable for consumers of the art form. The teardrop shape comes from water dripping from a faucet. As the water droplet falls, thanks to gravity, the top section pulls behind due to surface tension. This then creates the shape of a teardrop that we recognize.
But, in reality, raindrops aren’t shaped how they are depicted on television or art. Before we start on different shapes we need to establish the different sizes that raindrops can develop into. The size of a raindrop determines the shape it will take. The sizes are as followed: 1 millimeter, 2 millimeters, 3 millimeters, and 4.5 millimeters or larger.
1-millimeter size droplet: Droplets of this size are typically too small to be any other shape than a sphere. This is due to the surface tension of the water in the drop, the smaller the drop the stronger the surface tension will be.
2-3 millimeter size drops: As these droplets fall out of the cloud, they’ll begin to lose their spherical shape. This is the size that most drops tend to be, they are also the ones shaped like a hamburger bun. This shape is due to air pushing back up against the drop as it falls, creating the flat bottom. Airflow is greater at the bottom of the drop since it is falling. So, the pressure will also be greater at the bottom further proving that the bottom of a raindrop is flat or even slightly caved in (think kidney bean-shaped) at times. The domed shape at the top of the droplet is due to surface tension, which holds the drop together.
4.5 millimeters and greater: The larger the raindrop, the faster it’ll fall. This also means it is going to be affected by the air pushing up against the bottom of the drop more. Drops of this size, and larger, often become distorted and turn into an almost parachute shape. This shape is very unstable and eventually, it will break down into smaller droplets as it falls.
Diagram of raindrops based on size: