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ProvedGeometry·1999

Honeycomb Conjecture

Regular hexagons give the least-perimeter way to divide the plane into equal-area cells.

Formula

Honeycomb inequality
P2A83\frac{P^2}{A}\ge 8\sqrt{3}

For any partition of the plane into equal-area cells, the perimeter-to-area ratio is minimized by regular hexagons.

Hales' theorem (1999)
Regular hexagonal tiling minimizes iCi subject to Ci=1\text{Regular hexagonal tiling minimizes }\sum_i |\partial C_i|\text{ subject to }|C_i|=1

Thomas Hales proved that the honeycomb (regular hexagonal lattice) achieves the least-perimeter partition into equal areas.

Hexagonal optimality
A=332s2,P=6sPA=83A=\frac{3\sqrt{3}}{2}s^2,\quad P=6s\quad\Longrightarrow\quad\frac{P}{\sqrt{A}}=\sqrt{8\sqrt{3}}

The regular hexagon with side s achieves the exact lower bound — nature exploits this in honeycombs and basalt columns.

Summary

The honeycomb conjecture asks why hexagonal cells are optimal for equal-area partitions of the plane. Hales proved that the regular hexagonal tiling minimizes total perimeter.

Sources

Videos