John,
I think you are violating both the laws of physics and geometry. However, you are entitled to have that opinion.
So tell me how an object becomes lighter without subtracting molecules from it.
Hi John,
We went through this once before, didn't we?
A model is not an original object compressed down to a smaller size.
It is a completely different object, in most cases made out of different materials. The materials used have the same normal properties as any other earthly materials. They are simply fashioned into an object that "looks" like the original.
Now, if you ask, what would a 200 ton engine weigh if it were "compressed" down to O scale - that would be a totally different question and have nothing to do with modeling. It would still weigh 200 tons as you say.
It does bring up the question of how the surgical team, plus submarine, were miniaturized in the movie "Fantastic Voyage" before being injected into that guy's body. If they were just compressed and weighed the same, it would have been more than a little tough on the patient's body. 
Jim
