Although space travel has been a topic of great interest to many, few have an understanding of the ultimate limits that will determine its possibilities. One thing is certain. No matter the advancement in technology, whether earthling or extraterrestrial, energy requirements will determine ultimate success in space travel. True, technology will play a part. Among other things, it will determine the kinds of fuels that will be useable in deep space travel and that will, in the end, determine its successes. Are we ultimately going to be able to travel outside our own solar system to reach other worlds? Have extraterrestrials really visited us in the past? These are the questions addressed in this book. It is written for the layman, and does not require a technical background.