posted on Nov, 4 2009 @ 12:09 PM
You can apply physics to the size of people.
The structural support necessary for a giant is an interesting question.
I read somewhere that the thickness of the bones necessary to support a "giant" body becomes a limiting factor.
Also if you come from a giant planet, they you have to contend with the higher gravity associated with a larger planet.
I think that the aliens would look significantly different than us.