Hawking's book is an attempt to succinctly tell the history of the universe and the story of how humans figured that history out. He starts with Aristotle. It is hard to imagine the modern world of science without Aristotle's questioning mind guiding the way. He is the archetypal scientist and he provided the Western World with the first opportunity to examine reality without being forced to view it through a lens of divine motivations. The Earth was a sphere, whether or not the gods wanted it that way. Aristotle could prove it by observing how the North Star seemed to stay in an almost fixed point, and by reminding everyone that lunar eclipses always cast the Earth's circular shadow on the surface of the moon and only spheres always cast circular shadows. And that's about the last time Aristotle was right about anything! Still, he unquestionably deserves a mention in any history of modern science.
After mentioning Aristotle, Hawking fast forwards a couple thousand years to 1676. Eleven years before Newton's "Principia Mathematica" was published, a Danish astronomer named Ole Chistensen noticed that there was something wrong with the orbit of Jupiter's moons. Viewing them through telescopes, he noted that their eclipses behind the newly discovered planet did not happen with perfect regularity as they should. The rates of their orbits fluctuated by a few hours over the years. Instead of fabricating some elaborate hypothesis explaining how the speed of different moons' orbits could slow down and then sped up again over time, Christensen correctly postulated that this only seemed to be happening because the light from Jupiter takes much longer to reach the Earth when the two planets are on opposite sides of the solar system. The orbits were as regular as clockwork, but it takes a couple extra hours for light to travel that extra distance to reach the Earth. This is mind-blowing logic. This is something that would have never occurred to you and had never occurred to anyone else who had observed it. It takes these extraordinary leaps of counter-intuitive logic to move human knowledge into the modern era. Christensen was even able to closely guess the speed if light at 140,000 miles per second (it is actually a bit faster, 186,000 mps).
Just a decade later, Isaac Newton published his master work and changed everything about how humans think about the world around us. His laws of motion and force allowed humans to begin thinking about reality in new ways. His calculations weren't complete because he had no conception of general relativity, but even today Newton's Laws are accurate enough to successfully get spacecraft to other planets. His revelations were incomplete, but they were ground breaking and they paved the way for a whole new field of study. Soon afterwards, and for the first time, science was no longer the domain of philosophers, it was the realm of dedicated scientists, people who were solely interested in studying the creation rather than the creator.
A few hundred later, another genius with the gift of logical insight brought human understanding even farther than Christensen or Newton. Albert Einstein's theory of relativity states, not that everything is relative, but that all the laws of physics should be the same for all observers regardless of how they are moving. What is relative, is not any law of the universe, but the perspective of the observer. What made general relativity so revolutionary is not that it declared space or speed to be less than absolute, these were obvious truths. What made it so revolutionary is that it declared an end to the concept of absolute time! Time is a feature of the universe and is subject to the same relativity as matter or speed. How any person or object perceives the passage of time is unique to them.
Einstein also changed the way humans think about gravity. Gravity is not a force like any of the others traditional forces like magnetism or the weak and strong nuclear forces. Rather it is a consequence of the warping of space-time by mass and energy. When astronomers say that light can be bent around massive objects like galaxies or stars, what they really mean is that those massive bodies bend the very space the light is moving through. Light always moves in straight lines, but Einstein taught us that the space through which light moves can be curved by mass. He opened our eyes to the reality that everything in the universe interacts with everything else in far more intimate ways than we had ever imagined before. We are not simply attracted to other objects, our very mass warps space like children warp a trampoline so that we cannot help but fall towards one another.
You were shocked to read that the argument over the existence of atoms has raged for thousands of years (since Aristotle argued that they couldn't exist). It wasn't setttled once and for all until Einstein proved the existence of atoms in the early 20th century. That's how big of a deal World War II was in the course of human history. We went through 3,000 years of mystery and debate, but it only took us 30 years after the confirmation of atoms to use that knowledge to build a nuclear reactor and, soon after, a nuclear weapon.
Albert Einstein was the living embodiment of his most famous quote, "Imagination is more important than knowledge." But his imagination advanced the field of human knowledge like no other human in Earth's history.
Part of the problem with modern physics and cosmology is that the laws that appear to govern our universe at the largest of scales do not appear to govern that same universe at the smallest of scales. There is not yet any theory to merge Newton's Laws with what we know of quantum mechanics. But people like Stephen Hawking and others have been working for decades to link these two realities. On page 41, Hawking mentions the accidental discovery in 1965 that the universal background radiation is remarkably constant no matter where we look in the sky. This is not something anyone predicted. Just last month, however, we discovered that the minute variations in this radiation confirms quantum gravity and provides the first link between special relativity and quantum mechanics. This was something Hawking predicted in "A Brief History of Time." Henry from the YouTube channel "Minute Physics" explains better than you can about the new discovery of quantum gravity's effect on the fabric of the universe when it was very very new: https://www.youtube.com/watch?v=4IlBNJbCzfk&list=UUUHW94eEFW7hkUMVaZz4eDg
In fact, several of the things Hawking discusses in "A Brief History of Time" have since been confirmed. He argues that Einstein's theory predicted a singularity at the beginning of the universe and makes the case for the Big Bang. He describes the universe in the way we think of it today; not as an infinite expanse, but instead as a finite creation simply without any edge. He predicted that black holes, contrary to accepted beliefs about them, could actually emit heat and will eventually dissapear. He describes quantum and string theories and Heisenberg's uncertainty principle. But instead of detaiing all of the things he talks about here in this review, you decided you would rather keep this book on the shelf to reread it again.
"A Brief History of Time" conveys a charm that you did not expect. Stephen Hawking is not only famous for being one of the most brilliant minds alive today, but also for being almost completely paralyzed by Lou Gehrig's disease. His voice comes not from his larynx, but from a computer controlled by his eye movements. Nevertheless, his book sparkles with an excited tone no computer could ever convey. He becomes almost giddy when describing the details he recently discovered about black holes. His enthusiasm is infectious, and his sense of wonder is not dampened by his intellect or his disability.
Hawking describes his motivation at the end of the first chapter.
"But ever since the dawn of civilization, people have not been content to see events as unconnected and inexplicable. They have craved an understanding of the underlying order in the world. Today we still yearn to know why we are here and where we came from. Humanity's deepest desire for knowledge is justification enough for our continuing quest. And our goal is nothing less than a complete understanding of the universe we live in.""A Brief History of Time" reminded you that we all have this yearning. Ignorance is not bliss. The more we follow this instinct as a species the more we are able to grow beyond our limitations, the more we are able to understand the very fabric of the reality that knits us all together. If astrophysicists are correct, every atom in the universe that is more complex than hydrogen and helium was cooked together in the heart of a star that eventually exploded in a supernova. We are created from the stuff that was flung into space during those explosions. We are more than stardust. We are a way for the universe to know itself. As far as we know, humanity is the only manner in which all Creation is able to wonder at itself. "A Brief History of Time" reminded you again how wonderful that Creation is.
On to the next book!
P.S. This GIF is taken from the movie "Harry Potter and the Prisoner of Azkaban." Look again at what the wizard is reading while magically stirring his cup of tea in the Leaky Cauldron. "A Brief History of Time" is more than a 30 year old physics history book. It is a part of the cultural zeitgeist. And it deserves to be.