Week 3: constructor theory · constructor-theory
Information and substrate independence
See information as physical-but-substrate-independent; explain why digital computation works.
In this lesson
- Read the core idea (2 min).
- Walk through one worked example.
- Take the 4-question quiz; pass with 4/4 or better.
Hook
Most physicists agree, after Landauer, that information is physical — erasing a bit dissipates a minimum amount of heat, full stop. But information is also weirdly indifferent to what it rides on. The same email can be the bit-pattern of magnetic domains on a hard drive, of electric charges in DRAM, of ink on paper, of photons travelling down a fibre, of action potentials in your visual cortex. If information is a physical thing, why does it not care what kind of physical thing it is?
Constructor theory has a clean answer: information is physical-but-substrate-independent. Marletto and Deutsch's 2014 paper, Constructor Theory of Information, gives a precise definition by way of the constructor framework you have been building, and explains why digital computation works the same way on silicon, on paper, or on a Turing-style mechanical assembly.