Newton's laws of motion Newton in his "Philosophiæ Naturalis Principia Mathematica" ("Mathematical Principles of Natural Philosophy"), first published in 1687. Newton used them to explain and investigate the motion of many physical objects and systems. For example, in the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion. A fourth law is often also described in the bibliography, which states that forces add up like vectors, that is, that forces obey the principle of superposition. Newton's laws are applied to objects which are idealised as single point masses,
Three Laws of Robotics the Three Laws into "Lucky Starr and the Moons of Jupiter", noting that this "was a dead giveaway to Paul French's identity for even the most casual reader". In his short story "Evidence" Asimov lets his recurring character Dr. Susan Calvin expound a moral basis behind the Three Laws. Calvin points out that human beings are typically expected to refrain from harming other human beings (except in times of extreme duress like war, or to save a greater number) and this is equivalent to a robot's First Law. Likewise, according to Calvin, society expects individuals to obey instructions from recognized