The Physics of Agency, Part 3: The Kybit — A New Unit of Control

Series: Physics of Agency (Part 3 of 10)

Summary

Introduces the kybit as fundamental unit of control, analogous to the bit for information.

Definition: Kybits quantify intentional control using Kullback-Leibler (KL) divergence between initial and final probability distributions:

• KL(P

  Q) measures thermodynamic work required to rearrange probability distribution

• Always non-negative (zero only if distributions identical)

Examples:

• Forcing fair coin to heads: exactly 1 kybit (moving from 50/50 to 100/0)
• Biasing fair die: ~0.585 kybits (moving from uniform 1/6 to weighted distribution)

Physical Reality: Kybits represent real thermodynamic costs. Each kybit corresponds to minimum energy expenditure E_min = C × k × T × ln(2), analogous to Landauer’s principle.

Key Insight: Just as bits measure information, kybits measure agency’s influence on future outcomes.

Tags

• physics
• agency
• information-theory
• thermodynamics
• sequence

Cross-References

• Backward: The Physics of Agency, Part 2: Agency vs Drift – The Thermodynamic Basis of Agency
• Forward: The Physics of Agency, Part 4: The Law of Control Work — Agency Costs Energy
• Related: Landauer’s principle (thermodynamics of computation) [external]
• Related: KL divergence (information theory) [external]

Notes

• Kybit concept becomes central unit throughout axionic framework
• KL divergence provides rigorous mathematical foundation for “control”
• Bridges information theory and thermodynamics
• Sets up quantifiable approach to agency (can measure control)