Got to be honest, when I read the title of the thread I thought this was going in a totally different direction... I don't know why I clicked on it anyway but I am relieved to see that it is not in fact a pic of smooth balls. :2thumbsup:
Assuming that these hypothetical spheres are still composed of real atoms with electron valence shells and electron repulsion between surfaces is considered contact, then in fact the larger sphere would have more contact points than the smaller one. I suppose if all the spheres and surfaces were supernaturally perfect and devoid of any building block particles then the contact areas should be the same.
but we have not assigned a mass to either of the spheres, nor have we said anything about the substance from which the plane is made. For all we know, the spheres could have zero mass and the plane could be infinitely rigid. from a mathematical standpoint, the surface area contacting the plane is equal for both spheres, being zero. it contacts at a point. a point has no extension in any dimension, thus it's size is zero.
