The Atheist's Guide to Reality_ Enjoying Life Without Illusions - Alex Rosenberg [14]
It took the nineteenth and twentieth centuries to show not only that physics is correct about the basic stuff and how it works, but to begin to uncover the details of how the basic stuff can explain everything about all the rest of reality, including biology.
Remember the periodic table from your high school chemistry class? The nineteenth-century Russian chemist Dmitri Mendeleev came up with this table. But how could we be sure that Mendeleev got it right? His taxonomy of the fundamental elements was shown to be correct by physics, by the atomic theory and the electron theory that physicists discovered in the first half of the twentieth century. Atomic theory showed why each element had to have exactly the place in the table Mendeleev gave it as a result of the number of protons, electrons, and neutrons its atoms contain. For a hundred years or so, chemists had been painstakingly weighing and measuring the amounts of each element needed to make a compound. Suddenly all those recipes emerged from the numbers of electrons an atom of each element contains. Physics explains chemistry.
And chemistry explains biology. Respiration, reproduction, muscle movement, the nervous system, heredity and development—all of these components of our biology are now well understood as chemical processes, and these in turn are understood as physical processes. The history of the Nobel Prize in Physiology or Medicine, as it is formally called, along with the one in chemistry, is a century-long catalog of awards to scientists who have figured out which physical and chemical facts fix all those wonderfully complicated biological facts that constitute life.
On his television series in the 1970s, astronomer Carl Sagan used to say that we are all “star stuff.” Though he was ridiculed for it, he was of course exactly right: the human body is nothing but complex arrangements of “billions and billions” of atoms; and every atom in every one of our bodies was produced by reactions deep inside stars light-years away from Earth. These reactions have been chugging out the chemical elements for 13 billion years now. We literally are all just part of a physical universe. It’s a universe in which everything happens as a result of pushes and pulls of bits of matter and fields of force that physics understands almost completely and in enough quantitative detail to enable us to build space stations, pacemakers, robot vacuum cleaners, molecular soccer balls, and artificial chromosomes.
The phenomenal accuracy of its prediction, the unimaginable power of its technological application, and the breathtaking extent and detail of its explanations are powerful reasons to believe that physics is the whole truth about reality. As for the rest of reality above the subatomic, all we need to know is what things are physically composed of and how the parts are arranged in order to explain and predict their behavior to equal detail and precision. That goes for people, too.
Physics is causally closed and causally complete. The only causes in the universe are physical, and everything in the universe that has a cause has a physical cause. In fact, we can go further and confidently assert that the physical facts fix all the facts.
Let’s unpack that slogan—The physical facts fix all the facts. It means that the physical facts constitute or determine or bring about all the rest of the facts. Here’s a graphic way of thinking about it. There is some corner of space-time far from here and now, so far in fact that light signals have not yet reached us from that corner of the universe. Imagine that by some cosmic coincidence, every molecule, every atom in that distant