Stephen Hawking, a theoretical physicist, cosmologist, and author, has always tried to explain complex astrophysical phenomena in simple language that everyone can understand. The subtitle of this book is "a further explanation of a science classic made more accessible". To his surprise, his book A Brief History of Time was a bestseller and was on the top ten list for 237 weeks and sold one copy for every 750 people on Earth. The book was a remarkable success for a modern physics book. Many people were asking for a sequel to the book. A Brief History of Time explained how Newtonian Astrophysics described the laws that control planets and stars' movement. This book takes into consideration the most recent theoretical and observational results. How light speed is finite and constant at 299,792,458 m/s. Since the speed of light is constant, to explain the different observations for different observers, time must be relative. Producing the twin paradox, i.e., time slows d...