Credit should be given to Stephen Hawking for presenting scientific concepts and theories in such a way that a person without a background in science can understand them. Hawking takes the fascination of the common masses with black holes and builds it to a whole new level. The best thing about this book is the absence of complex mathematical equations although there are few complex mathematical concepts discussed in the book. In his own admission, Hawking says that he was advised that each mathematical equation would halve the readership of the book. In the end, he sticks with the cornerstone of general relativity and one of the most famous equations, E=mc2.
Hawking starts the discussion with the approach of ancient generations to the science. He describes the Ptolemaic approach to the universe. Ptolemy extended the earth-centric approach of early Greeks and it was adopted by the Church because it allowed the possibility of heaven, a concept so deeply ingrained in all the religions. Centuries later Galileo and Newton contested the Aristotelian approach. The basic difference between their approach was the method of reaching the conclusion. Galileo emphasized on the experimental verification while Aristotle believed that everything can be proven by abstract thought. And in that were laid the roots of modern science. In next few chapters, Hawking discusses the Big Bang Theory and Uncertainty Principle. Hawking ponders over "Who we are and how did we came here." He then proceeds to scientifically justify the Big Bang Theory. The Uncertainty Principle puts rest to the efforts to determine the present state of universe accurately. The Uncertainty Principle leads to the development of a new branch of science, i.e. quantum mechanics. Subatomic particles and nature of different forces are also discussed.
The black holes have caught the imagination of popular science since few decades. A black hole is formed when a star uses up its hydrogen fuel and then because of its gravity contracts inwards. Due to the strong gravitational forces, nothing can escape, not even the light. A new thinking has emerged which allows the detection of Gamma rays from black holes thus raising a possibility that black holes are not so black. Hawking uses quantum mechanics to reach a conclusion that the universe has always been there and will always be and thus, there is no need to have a creator God.
The most interesting concept is that of the time. There is a possibility that time can go backward, into the past. But this suggestion contradicts the second law of thermodynamics which says that a closed system always behaves in such a way that its entropy increases. Thus, movement back through the time is ruled out. Also, human memory remembers only the past, not the future. Then Hawking discusses the dream of physicists to have a unified theory to explain all the phenomena. So far many theories have been proposed, but a single theory to explain all of them is yet to come. Hawking accepts the possibility that no unified theory may be possible.
Hawking should be given full marks for explaining such topics in all simplicity. He ends the book with word portraits of Einstein, Galileo Galilei, and Isaac Newton. As in the introduction of this book Carl Sagan says that although adults do not care much about the understanding of the universe, children do. Adults often turn to religious concepts to explain the unanswerable questions. Hawking refutes religious concepts in this book in a convincing way.
