Sean Carroll is a theoretical physicist at the California Institute of Technology, the author of several popular science books and an award-winning scientist.
"The Big Picture" does exactly what its hugely ambitious title promises, and in the space of 433 pages. Quite a feat. He starts with with the deepest level of reality, with the Big Bang, the cosmos and the smallest particles in our universe and our daily lives. He demonstrates how everything is matter or energy. He expands on how scientists from the ancient Greeks tried to come to grasps with this elusive reality, how delving deeper provided answers yet created even more questions.
He expands on what we can know and how. He writes about the nature of science, of doubt and observation. How extremely difficult it is to understand and explain reality. How different levels of description fail to convey the exact nature of reality. How we have to accept uncertainty. And probability instead of accuracy.
In part three he goes into the "essence" of reality. Why does the universe exist at all? What are the smallest particles, how do they come into existence, and how do they interact? Carroll is confident that the big picture that we have today, the "Core Theory", is the correct one. This quantum field theory unites the standard model of physics and the general relativity. Our present understanding of quantum gravity includes everything we experience in our daily lives. it's the quantum field theory of the quarks, electrons, neutrinos, all the families of fermions, electromagnetism, gravity and nuclear forces, and the Higgs. "A thousand years from now we will have learned a lot more about the fundamental nature of physics, but we will still use the Core Theory to talk about this particular layer of reality (...) the laws of physics underlying everyday life are completely known". He concedes that "it's not the most elegant concoction that has ever been dreamed up in the mind of a physicist, but it's been spectacularly successful at accounting for every experiment ever performed in a laboratory here on earth".
On the cause of the universe or the question "why is there something instead of nothing?", he turns the situation around to account for the real findings in physics: "there is not a moment in time when there is no universe, and another moment in time when ther is; all moments in time are necessarily associated with an existing universe. The question is whether there can be a first such moment, an instant of time prior to which there were no other instants. That's a question our intuitions aren't up to addressing.
Said another way: even if the universe has a first moment in time, it's wrong to say that it "comes from nothing". That formulation places into our mind the idea that there was a state of being called "nothing", which then transformed into the universe. That's not right; there is no such thing as "transforming". What there is, simply, is a moment of time before which there were no other moments."
Not surprisingly, in this universe, there is no need for a god who created all this. The implications of the Core Theory are also clear for the existence of a soul : it just cannot possibly exist, and as a consequence, there is no possibility for something such as life after death to exist. We are all matter.
Then he takes us a step further, into the realm of life. How it began. Sure, Carroll is not a biologist, but he looks at biology with the mind of a physicist. He looks at how complexity can arise, and how the laws of entropy are completely compatible with it.
Then he looks at consciousness and the latest findings of neuroscience and cognitive sciences. Again, many questions remain about how the brain works, about how consciousness is created out of the electrical signals that are transmitted between the neurons in our brain.
In the final chapters he talks about the world, about morality. And here too, Carroll's words are wise, and well-substantiated.
It is by all means an amazing book, not only by the scope of the author's knowledge, the depth of his insights, the fluency with which he describes it, but also because of his scientific open-mindedness and care for humanity. Some could argue that it's a little too much, that a physicist should stick to his territory and not go beyond his field of knowledge. But why not? Physics has given us answers to questions that philosophers and theologians had been struggling with since forever. Few philosophers will understand quantum physics, but philosophy can be understood by physicists, just like morality. I think it's wonderful that someone dares make the connection between all the sciences. As long as its critical and well-informed, they should all be doing that.
Essential reading in any school in the world, regardless of the subjects chosen.
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