Kepler's laws of planetary motion of solar system body number "i" is, according to Newton's laws: where formula_72 is the mass of body "j", formula_73 is the distance between body "i" and body "j", formula_74 is the unit vector from body "i" towards body "j", and the vector summation is over all bodies in the world, besides "i" itself. In the special case where there are only two bodies in the world, Earth and Sun, the acceleration becomes which is the acceleration of the Kepler motion. So this Earth moves around the Sun according to Kepler's laws. If the two bodies in the world are
Three Laws of Robotics before his death. These three books, "Caliban", "Inferno" and "Utopia", introduce a new set of the Three Laws. The so-called New Laws are similar to Asimov's originals with the following differences: the First Law is modified to remove the "inaction" clause, the same modification made in "Little Lost Robot"; the Second Law is modified to require cooperation instead of obedience; the Third Law is modified so it is no longer superseded by the Second (i.e., a "New Law" robot cannot be ordered to destroy itself); finally, Allen adds a Fourth Law which instructs the robot to do "whatever it likes"