"... so long as we confine ourselves to the classical electrodynamic theory we cannot even understand why we obtain spectra consisting of sharp lines at all. This theory can even be said to be incompatible with the assumption of the existence of atoms possessing the structure we have described, in that the motions of the electrons would claim a continuous energy from the atom, which would cease only when the electrons had fallen into the nucleus."
January 1, 1970
https://en.wikiquote.org/wiki/Electron