I’ve been thinking about comments made by Fra in a number of threads, where he raises questions like – what does an observer “see” at the sub-atomic scale? We could make a long list of more and less reputable ideas about the fundamental information-processes in physics, going back to Wheeler’s slogan “It from Bit”. My own favorite approach is Carlo Rovelli’s “Relational QM”, which tries to derive the quantum formalism from information theory – but there are many variations on this theme. There’s also a lot of well-established theory directly relevant to the question of physical information-processes. The problem is, this is exactly where theories tend to become counter-intuitive and even contradictory. A couple of obvious examples – the issue in QM about when a physical interaction constitutes a “measurement”, or the problem of how “non-local” quantum correlations can occur, since Relativity limits physical communication to the speed of light. So despite all the relevant theory and experiment, we have no clear picture of what actually happens with information, in the physical world. As a result, the ideas about fundamental information-processes in physics tend just to be guesses, sometimes almost unrelated to all that’s known about QM and particle physics. There are three main points I want to make about this line of thought, which I’m putting in separate posts below. 1. Physical observation (communication) is not just recording (transmitting) data. This may be obvious, but it’s important because information-theory was to begin with a theory about data-transmission. 2. The actual information-processes in physics are anything but simple. Logically simple processes (like duplicating data) almost don’t occur in physics, while what does happen in physical interactions has an informational structure that’s profoundly complex, in more than one respect. 3. Observation (communication) in physics could be a process that defines itself recursively. This goes back to Rovelli’s interpretation of quantum measurement, and suggests a way that inherently complex information-processes might nevertheless be fundamental.