[Doug Egan]

History of science question here. I have long read that Rutherford was completely stunned by the results of his classic gold foil experiments.  My question is, what was his motivation for doing the experiment, if he was so convinced that he would just see the alpha particles pass through the gold foil, corresponding to Thomson's model.

Several sources quote him as saying  "It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."

Was he really just trying to find confirmation of Thomson's model (which implies that he had considered the possibility of a planetary model before doing the experiment)?  Or was he pursuing some other line of study and just happened upon this surprising result?  Most internet sources focus on his interpretation after doing the experiment, rather than his motivation for setting up the experiment in the first place.

[Borek]

From https://en.wikipedia.org/wiki/Plum_pudding_model:

"The plum pudding model usefully guided his student, Ernest Rutherford, to devise experiments to further explore the composition of atoms."

Different distributions of charge in the atom should produce different patterns/distributions of deflected alpha particles, so it is in a way an obvious experiment that should give some information about the structure of the atom.