In 1913 Niels Bohr proposed a model for the hydrogen atom in which the electron moved in a circular orbit around the nucleus, with the centrifugal force of the electron in the orbit just balanced by the electrostatic attraction of the nucleus.

To the question "Why doesn't the electron radiate energy and fall into the nucleus as electromagnetic theory predicts?", Bohr gave the blunt reply "It just doesn't."

The theory of oscillating dipoles and radiation may apply to radio antennae, he proposed, but not to things the size of atoms; just as the separate categories of wave and particle do not apply at that level.

For a cornerstone of his theory Bohr assumed that stable atoms could exist with electrons in circular orbits.