Unlike the amateur investigator of UFOs, both the storyteller and the physicist know that if and when such advances are made, they will enlarge our understanding of the cosmos, as did the creative insights of Galileo, Newton, and Einstein, but new discoveries cannot invalidate what we have already learned about how the universe works. Many of the properties ascribed to UFOs imply a complete breakdown of physical law. They belong to the realm of magic, not science. Traveling at speeds approaching the velocity of light, reversing direction instantaneously, achieving maximum acceleration or deceleration in a fraction of a second, becoming invisible at will--such feats are impossible for a solid body moving either in an atmosphere or in space. Most of the serious proponents of the saucer hypothesis acknowledge that such actions are impossible, according to our present knowledge, but they argue that alien races more advanced than earthmen have undoubtedly found new sources of power and developed new methods of propulsion. Elaborate theories have been constructed, phrased in nearly incomprehensible scientific jargon, to show that UFOs do not flout the laws of physics but merely operate under laws that are still unknown to human beings. To UFO investigators whose professional training lies chiefly in fields other than physics--business, the arts, entertainment, military science, government, the law, medicine, or religion--such theories might well seem plausible. But to the physicist they seem so irrational that they do not even deserve discussion, and he dismisses them as nonsense. Saucer believers thereupon denounce the physicist as a bigot, complain of his “closed mind,” and piously invoke the ghost of Galileo. They forget, apparently, that the persecutors of Galileo were specialists in theology and had only a nodding acquaintance with astronomy. One of the earliest theories of UFO propulsion suggested that saucers got their motive power by tapping the lines of force in the earth’s magnetic field. One author wrote: “The earth being simply a huge magnet, a dynamo wound with magnetic lines of force as its coils, tenescopically [the meaning of this impressive word is unknown to the present authors] counted to be 1,257 to the square centimeter in one direction and 1,850 to the square centimeter in the other direction (eddy currents), indicates that natural law has placed these lines as close together as the hairs on one’s head. And yet they never touch or cross each other if let alone. If done so by accident the catastrophe would spread like a searchlight and destroy everything in its path.”[IX-20, p. 139]