Kelvin's foam structure: a commentary

Kelvin's 1887 speculation on an ideal foam structure, which was intended to serve as a model for the ether, was a highly imaginative conception, brilliantly carried through into detailed calculations. It eventually launched the Kelvin Problem, which asks how space may be partitioned into cells of fixed equal volume with minimum surface area. Although it could be said to be misguided in motivation, faulty in logic and even mistaken in its conclusions, the paper nevertheless stands as an enduring classic and Kelvin's foam remains of great interest today.