Bohr began to work on the problem of the atom's structure. Ernest Rutherford had recently suggested the atom had a miniature, dense nucleus surrounded by a cloud of nearly weightless electrons.

Philip Ball looks at how a little-known paper by Niels Bohr demonstrates the turmoil in physics on the brink of quantum ...

Photo: Niels Bohr's research notes for his new atomic theory Rutherford's find came from a very strange experience. Everyone at that time imagined the atom as a "plum pudding." That is ...