Klein demonstrates that the fifth dimension (fourth spatial dimension) must be 10-35 m, or the Planck length. In 1919, Kaluza, introducing a fifth dimension, described light as a disturbance in this fifth dimension. Kaluza thus found the first clue to transforming wood into marble. The marbling of physics, as Einstein intended it, who saw space-time as “marble”: clean, beautiful, elegant, while matter is “wood,” or a hideous, confusing collection of random shapes (referring to the plethora of particles and subparticles that form crystals, rocks, etc.).
