Kepler conjecture

The Kepler conjecture is a problem in math. It wants to know the best way to put spheres together so there will be only a little bit of room between the spheres. That means the spheres are put together very tightly, meaning they are dense.

One of the diagrams from Strena Seu de Nive Sexangula, illustrating the Kepler conjecture

Details

The Kepler conjecture is about Sphere packing in three-dimensional Euclidean space. It is named after Johannes Kepler (1571-1630) who first had this idea. Kepler supposed that the ways to pack spheres of equal size that result in the packing with the highest density are face-centered cubic or hexagonal packings. Those two things are crystal structures, meaning ways to put things together in a repeating pattern. These packings have a density of slightly over 74 percent, this means that they fill about 74 percent of space available.