Tuesday, July 05, 2016

To Explain The World: by Steven Weinberg

Steven Weinberg's To Explain The World provides a very good introduction to the age of scientific discovery. Weinberg's goal is to explain how the early scientists incrementally developed the scientific method as they were learning, developing new theory, and testing their ideas, but I thought the presentation also did an amazing job of explaining the context of the discoveries in a way that made each contribution much more understandable. I've read many histories of science, so few of the foreground facts (who discovered what and when) were new to me, but being reminded about what else was going on at the time, and which people had been talking to (or arguing with) one another gave more context and made it easier to judge the relevance and difficulty of their accomplishments.

Weinberg starts with the ancient greeks, and explains how they were interested in the nature of reality, and our place in the cosmos, but had no concept of comparing their proposed explanations to the world or in any way testing their ideas. In some ways, some of those whose names live on were proposing better solutions than any that would appear for thousands of years, but without demonstrations of their truth or applicability, they wouldn't be influential until rediscovered in later circumstances, where better scientific methods would allow them to take part in a system of understanding.

In the hellenistic period in Egypt after the death of Alexander, individuals were able to figure out that falling objects accelerate, that air is a real substance that can displace water, and to invent effective pumps and accurate water clocks. When they made useful artifacts, their ideas had consequences and were remembered. When they theorized ex nihilo, they were more evanescent and didn't effect many later thinkers. Around this time, Archimedes systematized approaches to the simple machines, and recorded drawings of many useful tools built from screws, ramps, levers, and pulleys.

Starting from their certainty that heavenly bodies must move in circles, Plato asked some of his students what combinations of circular motions could produce the wandering motions of the seven known planets against the starry background that the Greeks could see with their unaided eyes. The pattern of inventing and compounding epicycles would continue until the time of Kepler.

Weinberg's final word on Leibniz and Newton is illustrative of how he analyzes the interactions between scientists, and looks for their influences on one another and on progress generally.

The judgement of contemporary scholars is that Leibniz and Newton had discovered the calculus independently. Newton accomplished this a decade earlier than Leibniz, but Leibniz deserves great credit for publishing his work. In contrast, after his original effort in 1671 to find a publisher for his treatise on calculus, Newton allowed this work to remain hidden until he was forced into the open by the controversy with Leibniz. The decision to go public is generally a critical element in the process of scientific discovery. It represents a judgement by the author that the work is correct and ready to be used by other scientists. For this reason, the credit for a scientific discovery today usually goes to the first to publish. But though Leibniz was the first to publish on calculus, as we shall see it was Newton rather than Leibniz who applied calculus to problems in science. Though, like Descartes, Leibniz was a great mathematics whose philosophical work is much admired, he made no important contributions to natural science.

Weinberg gives credit to the Greeks for discovering and passing on the idea that nature follows consistent rules, and that we can use mathematics to build models which will help us explain and understand them. It wasn't until the 17th century however, that scientists realized that this can be applied pervasively, and actively looked for opportunities to explore new phenomena and describe them mathematically. The final two thirds of the book is a discussion of the conversation that arose among scientists as they investigated, shared observations, and looked for ways to apply fewer and broader explanations to more and more fields.

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