Abstract

When at the end of the 1900s Planck introduced the constant h into the black-body radiation law together with constant k, he provided no explanation of either its meaning or why it had that particular value. He simply introduced it. In reality the history of the constant was far from straightforward. Planck was confident enough to introduce it like this because he had been working on the question for over a year. In this paper we reconstruct the process that began with the first two constants (c' and C