Our world is full of gorgeous and fascinating displays of a variety of weather-related phenomena. From the upbeat nature of sunny days, to the dreary feeling of an overcast sky, to the enchanting views of a snowfall, there is no shortage of different weather to enjoy. Rain has mystified us since the day we could comprehend it. Various cultures and religious beliefs came up with their own versions of how and why rain falls, but we didn’t get a straight and concrete answer until we hit the Scientific Age.
Unlike the water beads that drip from your bathroom faucet, rain-drops are not tear-shaped. They are fattened globules having a somewhat concave bottom. Other things being equal, almost all droplets of water are spherical, the most compact of shapes. Raindrops begin their fall as spheres and would arrive that way but for the pounding that they receive from two intervening forces.
The first of these sculptors is hydrostatic pressure, which causes the bottom portion of a liquid mass to compress and flatten in response to the weight of the upper portion. Although raindrops are feather light, they are subject to this phenomenon and are shaped by it. As the drops fall, aerodynamic pressure – the force of air on an object moving through it resists their downward course and indents their bottoms. That’s the second influence.
The largest raindrops are the most affected. Many drops are destroyed entirely and burst into countless watery bits – each sustaining yet more distortion until a pavement, lawn, or your umbrella ends its fall. The diameter of most raindrops ranges from 0.5 to 6 millimeters. The largest drops fall at the rate of nearly 9 meters per second, whereas the smallest have a leisurely speed of 2 meters per second.
The smallest raindrops retain their spherical shape right up to the point where they splash on to some surface. Bigger raindrops are usually shaped like a burger bun; with the top being round and the bottom being rather flat. The biggest and heaviest of the raindrops actually take on the shape of a parachute. Their mass is too much for them to retain a stable form, and thus the air pressure forces the raindrop to curve upward from the middle of the bottom.
This curve continues to go upwards until the raindrop splits in two. If the resulting raindrops are still too large, the same process of the parachute shape repeats. If the raindrops are not large or heavy enough, they usually take on the burger bun shape. And if they are too small, or break apart again into much smaller parts, they become spherical in shape.
Tear-shaped raindrops do not exist in any scenario. Though raindrops have mostly been depicted in media as tear-shaped, and the look is sort of iconic to them now, it only gained popularity because people saw tear drops and drops from a tap and thought raindrops must look like that too. In reality, tear drops and drops from a tap drop much too slow and too small a distance to face air resistance. This means most of their mass is pulled downward by gravity and that gives them the tear drop look. Rain drops face air resistance magnitudes higher than tear drops, and cannot help but take on different shapes as they hit freefall.