I first met Martin Rees in Cambridge in I think it was 1967. I very much respect his scientific work, but I think he has severely distorted the facts about UFOs whether by intent for national security reasons or simply lack of due diligence in what is a political not a scientific issue. Indeed, Martin Gardner in Science, Good, Bad & Bogus mentioned that physicists like myself do not make good paranormal investigators. Similarly, astronomers do not not make good UFO investigators. My contacts with the Intelligence Community & Military lead me to believe that some UFOs are real machines with advanced low-power warp-drive technology. I presented an invited paper on this to the DARPA-NASA 100 year starship meeting in Orlando Oct 1, 2011 - expenses paid by DARPA. Furthermore, in my opinion, the advanced time-traveling intelligence operating these machines have manipulated us for thousands of years. Indeed, we are genetically engineered by them. For additional background information see MIT physics professor David Kaiser's book "How the Hippies Saved Physics" and my Wikipedia page as well as Martin Gardner's book.