A book is kept on the surface of a table. If the gravitational pull of the earth on the book is the force of action, then the force of reaction is exerted by

According to Newton's Third Law of Motion, forces always exist in pairs that are equal in magnitude and opposite in direction, acting on two different bodies [t8][t10]. A common misconception is that the normal force from the table is the reaction to gravity; however, these are different types of forces acting on the same object [t1][t6]. For a true action-reaction pair, the forces must be of the same nature [t2]. If the 'action' is the gravitational pull of the Earth on the book, the 'reaction' must be the gravitational pull of the book on the Earth [t1][t3]. While the book also exerts a contact force on the table, that is the reaction to the table's normal force on the book, not the reaction to the Earth's gravity [t1][t5]. Thus, the book attracts the Earth with the same gravitational force that the Earth exerts on the book [t8].