In "The Imagined Conflict", chapter 6 "Evolution and Purpose", ends like this:
Newton’s law of gravitation was a breakthrough because it united the large and small. It could describe everything from how stones fell on Earth, to the stability of planetary orbits. The world seemed to work like a clock, just like the early mechanical clocks. The prime example is the one from 1386 in the cathedral in Salisbury, England, which is the world’s oldest functioning clock. This mechanistic view of nature took over from the more organic view that the Medieval Age had from Aristotle. It played a crucial role during the Enlightenment of the eighteenth century, when Laplace also came up with a description of how a planetary system could form. In principle, everything could now be calculated, if the initial conditions were known. It was believed that these laws not only described nature but also explained why nature works. They had forgotten the insight of Newton, Boyle, Kepler, and Galileo that the laws were just describing how, not the why of the universe.
In the twentieth century, the belief in determinism in physics was challenged. This was particularly true of quantum theory. In quantum mechanics, Heisenberg’s uncertainty principle says that it is not possible to know both the velocity and position of a particle. This is not because we have poor measuring instruments, but it is a fundamental fact about nature. Quantum uncertainty applies at the micro-level, and we can probably ignore it when we talk about larger objects like stones and planets and even brains. However, over the past few generations, it has become clearer that even for such phenomena, there can be uncertainty. According to chaos theory, certain complex systems are so sensitive to small changes in the initial conditions that it is impossible to calculate what the future will be. The weather is a good example. We currently work with a limit of a week or two on how far into the future the weather can be predicted with some certainty. It’s possible that this period can be extended with better models, but it seems that there may still be a limit to how far into the future we can predict something as chaotic as the weather.
In cosmology, building on Einstein’s relativity theory, it is also understood that the big bang marks a first event, and that it is impossible to say anything about what may have been before that. Even time started then. If we are to believe the measurements, there are indications that the universe is expanding faster and faster as time goes by. This requires the existence of an unknown dark energy with negative gravity that “rips” the universe apart. There is also something called dark matter, which is the invisible mass needed to describe why galaxies behave the way they do. Dark matter only affects gravitation, not electromagnetic waves like light, and is therefore impossible to detect with ordinary instrumen
The point of this is to show that physics has moved from a mechanical view of everything, to realizing that there are limits to how accurately we can predict the future. Physics has also shifted from believing that it has complete oversight to having to reckon with both dark energy and dark matter, where “dark” is just a nicer word to express that this is something we don’t know about and cannot observe directly.
Biology, with the central role of neo-Darwinism, may be where physics was during the Enlightenment: everything is determined by genes, and humans are “nothing more than” genes ensuring their survival. It reminds me of the confidence of the mechanistic physicists in the generation after Newton when a present-day biologist can bring himself to say that “evolutionary theory is the best-understood theory in science, the best justified, and the best documented.” Hopefully biology will grow up, just as physics has had to do, to a more mature and humble view, and maybe the extended evolutionary synthesis will show the way.
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