Show HN: Python Simulator of David Deutsch’s "Constructor Theory of Time"

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A Python implementation of David Deutsch’s Constructor Theory framework, exposing key concepts—from simple Tasks and branching substrates to quantum-gravity and electromagnetism—entirely in code. Includes a “universal constructor” that can bootstrap itself from a list of Tasks, demonstrating self-replication and the power of Constructor Theory.

“A demonstration of how constructor theory could be explored in code, not a high-precision physics engine. For the formal definitions, see David Deutsch and Chiara Marletto’s recent paper “Constructor Theory of Time” (May 13, 2025).

Core framework: Attributes, Substrates, Tasks, Constructors
Irreversible & quantum tasks: Many-worlds branching, decoherence guards
Timers & Clocks: Simulate proper-time, special/general relativity corrections
Fungibility & SwapConstructor: Free exchange of identical substrates
ASCII visualizer: ascii_branch() for quick text-based branch inspection
Continuous dynamics: 1D & 2D substrates, DynamicsTask, RK4 & symplectic integrators
Coupling tasks:
- Gravitational two-body (1D)
- Coulomb coupling (1D)
- Lorentz-force (2D) for charged particles in a magnetic field
Quantum-Gravity & Electromagnetism: Graviton & Photon emission/absorption Tasks
UniversalConstructor: Bootstraps any list of Tasks into a working Constructor
Demo scripts:
- demo.py – shows every constructor in action
- bootstrap_demo.py – elegant self-replication via the UniversalConstructor

Python 3.8+
(Optional) matplotlib for phase-space plots

git clone https://github.com/gvelesandro/constructor-theory-simulator.git cd constructor-theory-simulator

python -m unittest ct_tests.py

python demo.py python bootstrap_demo.py

Note: If you don’t have matplotlib, the demos will still run; plots will simply be skipped with a warning.

from ct_framework import ( Attribute, Substrate, PhotonEmissionTask, PhotonAbsorptionTask, UniversalConstructor, ascii_branch ) # 1) Define your “program” of photon Tasks ELEC = Attribute("charge_site") prog = [ PhotonEmissionTask(ELEC, emission_energy=5.0, carry_residual=False), PhotonAbsorptionTask(ELEC, absorption_energy=5.0) ] # 2) Build a Constructor at runtime uc = UniversalConstructor() em_cons = uc.build(prog) # 3) Emit a photon atom = Substrate("A", ELEC, energy=20.0) branches = em_cons.perform(atom) print(ascii_branch(branches)) # => * charge_site (A) # * photon (A) # 4) Absorb it back photon = next(w for w in branches if w.attr.label=="photon") restored = em_cons.perform(photon)[0] print(restored) # => A:charge_site(E=20.0,Q=0,t=2,F=charge_site)

This is intended as an educational resource and proof-of-concept. Contributions are very welcome! Please:

File issues for missing tasks or physics modules
Submit pull requests for new constructors (e.g. chemical reactions, friction)
Improve documentation or add more demos

Released under the MIT License.

Inspired by David Deutsch and Chiara Marletto’s work in Constructor Theory and their May 13, 2025 paper “Constructor Theory of Time.”
Thanks to the quantum-foundations community for feedback and discussion.

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