Oct 3, 2013

The actual shape of a raindrop

Although a raindrop has been illustrated as being pear-shaped or tear-shaped, high-speed photographs reveal that a large raindrop has a spherical shape with a hole not quite through it (giving it a doughnut-like shape). Water surface tension pulls the drop into this shape. As a drop larger than 0.08 inches (2 millimeters) in diameter falls, it will become distorted. Air pressure flattens its bottom and its sides bulge. If it becomes larger than 0.25 inches (6.4 millimeters) across, it will keep spreading crosswise as it falls and will bulge more at its sides, while at the same time, its middle will thin into a bow-tie shape. Eventually in its path downward, it will divide into two smaller spherical drops. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)