It would seem to be useful to start with the question of representing the position of a particle with other particles. For any situation, you will need some dyn

It would seem to be useful to start with the question of representing the position of a particle with other particles. For any situation, you will need some dynamic range of measurement to describe the properties of a particle. Classical position might want 10 bits, interpreted as meters. With 6 numbers (position and momentum in 3 directions) that's 60 bits per particle. Even at 1 particular per bit, that's still a ratio of 60:1. And 10 bits is certainly not enough for some phenomena! The bottom line is that if you converted the universe to computronium, the absolute best you could do is simulate a universe 1/60th the complexity. In real life we do many orders of magnitude worse, memory cells require millions of atoms. This also doesn't deal at all with the computation required to advance the state of the system. Perhaps by focusing on the experience of life you can make the ratio make sense again. E.g. don't simulate particles, simulate minds (for which a particle is only an abstraction anyway), and you recover that ratio, and more.