The real shape of rain

While songwriters have long thrown teardrops and raindrops into the same lyric for emotional effect, artists often use the former to illustrate the latter. Imagine the shock of a youngster if you told them that raindrops are actually shaped more like hamburger buns than teardrops. The tiniest cloud droplets are almost perfectly spherical, but as they increase in size, there's more water inside relative to the surface area of the droplet. This means there's less surface tension to keep the sphere tight, so the droplet slowly evolves into a more oblong shape as it descends. A full-sized raindrop falls with its flat face downward. The pressure of the air below can form a dimple at the drop's centre (think of a doughnut whose hole isn't fully punched through). When we watch raindrops fall, our eyes may be tricking us into seeing a teardrop – the speed of the drop can produce a persistence effect in our visual field, much as the blur of a speeding car makes it seem longer than it is.