Tasks and substrates

Week 3: constructor theory · constructor-theory

Tasks and substrates

Re-express physics in terms of which transformations can and cannot be performed on substrates.

In this lesson

  1. Read the core idea (2 min).
  2. Walk through one worked example.
  3. Take the 4-question quiz; pass with 4/4 or better.

Hook

Most physics is written in the language of initial conditions and dynamical laws: tell me where every particle is and how fast it is moving, plug into the equations, and the future falls out. Constructor theory, developed by Chiara Marletto and David Deutsch, asks a different question. Instead of starting from "what will happen?", it starts from "which physical transformations can be reliably caused to happen, and which cannot?"

This is not a quirky reformulation. It is a bid to give physics a new layer underneath dynamical laws — a layer about substrates (physical things that bear properties), tasks (specifications of input-to-output transformations), and constructors (anything that can perform a task with high reliability and remain ready to do it again).