Re: Reaction to weight
I think, the reaction force is due to the long range interatomic force in the material of the table.
When you press the atoms of the table the electrons i the orbits of the atoms in the material of the table try to distort. When they distort, it tries to force the electrons fro their stable orbit to the lower orbits which are already filled up. Therefore according to Pauli's exclusion principle the lower orbit cannot afford any more electron and exerts repelling force on the intruding electron which pushes the electron away and in turn pushes the thing up as reaction force.