Paul Hill was a well-respected NASA scientist when, in the early 1950s, he had a UFO sighting. Soon after, he built the first flying platform and was able to duplicate the UFO's tilt-to-control manoeuvres. Official policy, however, prevented him from proclaiming his findings. For the next 25 years, Hill acted as an unofficial clearing house at NASA, collecting and analysing sightings' reports for physical properties, propulsion possibilities, dynamics, etc. To refute claims that UFOs defy the laws of physics, he had to make 'technological sense ... of the unconventional object'. After his retirement from NASA, Hill finally completed his remarkable analysis. This book, published posthumously, presents his findings that UFOs 'obey, not defy', the laws of physics.