On December 20, 1910, New Zealand born physicist Ernest Rutherford made his seminal gold foil experiment which led to first insight about the nature of the inner structure of the atom and to the postulation of Rutherford's concept of the "nucleus", his greatest contribution to physics. Most interestingly, Rutherford made his greatest discovery after receiving the Nobel Prize in chemistry in 1908.
On January 3, 1851, French physicist Leon Foucault started to experiment with his eponymous pendulum, by which he was able to proof the earth's rotation. Actually, how can you prove that the earth is a rotating orb in an easy-to-see experiment and - of course - without space flight? By today, Foucault's simple device is part of numerous natural science museums around the world.
J. Scheer, K. Bruning, T. Frohlich, P. Wurz, and W. Heiland. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 157 (1-4):
208--213(August 1999)