As the repair jobs got more and more complicated, I got better and better, and more elaborate. I bought myself a milliammeter in New York and converted it into a voltmeter that had different scales on it by using the right lengths (which I calculated) of very fine copper wire. It wasn’t very accurate, but it was good enough to tell whether things were in the right ballpark at different connections in those radio sets.In order to do this kind of thing — in order to modify a milliammeter, designed to measure electric current in milliamperes, into a device that measures volts — you need to have a functional understanding of the first principles behind the device. If you understand electricity well enough, then you understand what the device is doing to measure it, and then you can change it. Feynman elaborates:
Radio circuits were much easier to understand in those days because everything was out in the open. After you took it apart (it was a big problem to find the right screws), you could see this was a resistor, that’s a condenser, here’s a this, there’s a that; they were all labeled.And if wax had been dripping from the condenser, it was too hot and you could tell that the condenser was burned out…So it wasn’t hard for me to fix a radio by understanding what was going on inside, noticing that something wasn’t working right, and fixing it.This goes for all kinds of modern things, too. If you understand the way computers work on the component level (so hard drives, processors, graphics cards, etc), it’s not such a big deal to open one up and move things around, or replace others. This is repair work. First principles is a tricky concept today though, because things are so complex. Is knowing how to move components around inside a computer really first principles? Or is that a false understanding, because you need to also know how those components are put together? For practical purposes therefore, I think that you can call it first principles if you fully understand things at least a layer down from what you’re trying to work on. If it’s a computer, components are good enough. If it’s a battery, material costs are good enough. If it’s a program, the programming language is good enough. Living by first principles can help with the boring stuff as well as the important stuff. I have a Harmony remote for my TV and all the related gadgets, which mostly works, but sometimes doesn’t. If you take the effort to understand what the remote is doing (mimicking the signals from each individual remote in sequence) then it’s often not hard to know what went wrong and how to fix it. If, however, you don’t know what it’s doing, then it’s easy to get frustrated by it. The point is that first principles applies well beyond the areas of science and invention. It often takes a little extra effort, but if you build a habit around it, you will be approaching what you do in life with a distinct advantage, from the television to the future of transportation.