Robert Powell, a founding Board member of the Scientific Coalition for UAP Studies, has studied the UFO subject for 17 years. His work is encapsulated in A Scientist Explains What We Know (And Don't Know) which provides a scientific rationale for the reality of non-terrestrial craft that are intelligently controlled. Powell begins his book by familiarizing the reader with the history of UFOs and he identifies the more enigmatic and interesting UFO sightings. He examines the characteristics of these sightings that argue against a prosaic extreme acceleration, electromagnetic interference, bending light, no obvious propulsion mechanisms, and a lack of interaction with the atmosphere. Powell discusses the recent events that have caused our government to change the term from UFO to UAP. Included is information never before released indicating the government possesses not just two videos but five videos from 2015 of UFOs operating in the vicinity of the USS Roosevelt nuclear aircraft carrier.Powell's later chapters in the book discuss the extraterrestrial hypothesis considering the thousands of exoplanets that have been discovered in the last twenty years. Powell challenges the reader to consider all the implications that must be considered if intelligent life discovers us first. He looks at how we as individuals and as a society react to UFOs. He documents actions taken by our military that include instances when we have fired on UFOs. Powell argues that it is time for a change in the study of UFOs. The phenomenon has been with us for 75 years and we have learned very little as the decades have passed. The author makes the case for what needs to be done going forward. The solution he proposes will require a paradigm shift in our thinking and his book provides the information needed to understand that paradigm shift.