I have heard 2 informal explanations for the normal force during a situation like a book resting on a table: 1. The springiness of the atomic lattice in the table attempts to restore its original structure, thus pushing the book. 2. Since there are electrons on the outside of both the book and the table, the book is prevented from falling through (- repels -). Some even say this is the Pauli exclusion principle, not just electrostatic forces. Those particles cant occupy space already occupied. Which one is correct, or are they both correct? Then, if 2 is correct, say you wanted to float the book above the table using electrostatic forces. Would you need to put a charge on both the book and the table? Or could you just put a charge on the table and let induction push the book up (since all the electrons rush to the top of the book)? Thanks.