How apples get their shapes

Using theory, numerical simulations and lab experiments, a team led by UCL and Harvard researchers have shown for the first time how apples get their distinct shape. Apples are among the oldest and most recognisable fruits in the world. Humans have been drawing apples for millennia - their likeness has been captured by everyone from Caravaggio to Picasso. The new study, published , looked at the apple's shape, in particular the dimple or cusp at the top, where the stem grows. It described the shape using singularity theory, a long-standing mathematical theory used to understand phenomena where some property is infinite, ranging from black holes to cracks in the ground to pieces of string. The researchers demonstrated that the apple cusp  - the curve going down towards the stem, and then sloping back up on the other side - was a singularity, exhibiting the same 2D shape as a droplet of water as it breaks from a column, a pattern of light in a swimming pool, or water in a bath as it drains down a plug hole. Co-lead author Dr Thomas Michaels (UCL Physics & Astronomy) said: "What is exciting about singularities is that they are universal.