Paradox of radiation of charged particles in a gravitational field continuously "upward". Whether the acceleration is from motion or from gravity makes no difference in the laws of physics. One can also understand it in terms of the equivalence of so-called gravitational mass and inertial mass. The mass in Newton's law of universal gravitation (gravitational mass) is the same as the mass in Newton's second law of motion (inertial mass). They cancel out when equated, with the result discovered by Galileo Galilei in 1638, that all bodies fall at the same rate in a gravitational field, independent of their mass. A famous demonstration of this principle was performed on the
Three Laws of Robotics stated explicitly. Several years later Asimov's friend Randall Garrett attributed the Laws to a symbiotic partnership between the two men – a suggestion that Asimov adopted enthusiastically. According to his autobiographical writings, Asimov included the First Law's "inaction" clause because of Arthur Hugh Clough's poem "The Latest Decalogue" (), which includes the satirical lines "Thou shalt not kill, but needst not strive / officiously to keep alive". Although Asimov pins the creation of the Three Laws on one particular date, their appearance in his literature happened over a period. He wrote two robot stories with no explicit mention of the