I read this link
And understand from it that the scattering pattern is consistent with an alpha particle colliding with a much more massive particle.
Like a billiard ball colliding with a bowling ball, there will be a fraction on billiard balls that bounce back. (unlike two billiard ball collisions where a head on collision never results in a reflection back - unless the impacting billiard ball has a lot of backspin which we ignore in this experiment because alpha particles don’t have backspin)
But why did he conclude that there was only one such particle? And why did he conclude that it was at the center?
I know that sounds stupid and someone will bring up a symmetry argument. But consider that the distance between the origin of the alpha particle and its collision >>> diameter of massive object it is colliding with. So where the massive object really is in its neighborhood is really unknown. And if you don’t know where it is in its neighborhood, who is to say that the next collision did not occur in a different region of the neighborhood? So the massive particle may have had its one ‘orbit’ or random motion? Or that the next collisions occurred with another massive particle or particles entirely?