Credit: © NPG 1909

Hidden in the yellowing pages of century-old issues of Nature are some scientific gems. They might be fully fledged 'Letters to the Editor', curiosities from 'Notes' or nuggets from 'Our Astronomical Column'. Even the simple listings in 'Diary of Societies', at the end of each issue, can be fascinating — as is this entry (pictured) from the issue of 17 June 1909.

At the behest of their boss, Ernest Rutherford, at the University of Manchester, Hans Geiger and Ernest Marsden had been conducting experiments on the scattering of α particles from a thin gold foil. On that June afternoon — a century ago — they were to present to London's Royal Society their data “On the Diffuse Reflection of the α Particles” (Proc. R. Soc. A 82, 495–500; 1909).

The rest really is history. Geiger and Marsden had observed that, although most α particles passed through the foil pretty much undeflected, very occasionally — and contrary to expectation — an a particle could be scattered right back, through a very large angle. Rutherford had the interpretation: “the atom consists of a central charge supposed concentrated at a point”, he wrote later (Phil. Mag. 21, 669–688; 1911); the atom, far from being the 'plum pudding' that had been envisaged, had a nucleus.

Rutherford acknowledged that the essence of his nuclear model had been captured in the 'Saturnian atom' of Japanese physicist Hantaro Nagaoka (Phil. Mag. 7, 445–455; 1904), “which he supposed consisted of a central attracting mass surrounded by rings of rotating electrons”. But it was these data from Geiger and Marsden in 1909, and those that followed, that enabled the detail of the structure of the atom to be drawn more accurately than ever before. The nucleus was revealed, and a century of nuclear physics began.