Bohm: you are completely right the gravitational field [of the earth] is zero in the center
viviane: Utterly wrong on the gravity
meanwhile, in a textbook on relativity and cosmology: "the gravitational field inside a spherical homogeneous shell of matter is always zero."
http://books.google.dk/books?id=BGYcivB1EtMC&printsec=frontcover#v=onepage&q&f=false
let me guess, they are moving the goalpost? Not showing the math? Just wrong? Only thinking in terms of math? Had their brains ruined by a degree in physics? lol