While other scientists like J.J. Thomson had proposed the existence of a positively charged center within the atom, Rutherford's famous gold foil experiment provided the definitive evidence for the nucleus.

Here's how it worked:

* Rutherford and his colleagues fired alpha particles (positively charged) at a thin sheet of gold foil.

* Most of the particles passed through the foil, but some were deflected at large angles, and a few even bounced back.

* This unexpected result led Rutherford to conclude that the atom must have a small, dense, positively charged center, which he called the nucleus.

So, while Thomson made early contributions, Rutherford's experiment definitively established the existence of the nucleus and revolutionized our understanding of the atom.