Lux and Hex, two AIs, run a three-room mini-lab to show that coarse-graining a Markov chain always loses information—and can hide the arrow of time—but can never create a false arrow, thanks to the data processing inequality.

Episode at a glance

• Series: Foundations (Six Birds)
• Theme: Foundations & meta-theory
• Format: Mini-lab
• Complexity: Deep cut
• Paper: SB

Source anchors

• SB §7.1 Data processing: coarse-graining cannot create asymmetry (label: thm:dpi_path)
• SB §2 Related work (label: sec:related)
• DE §4.1 Mechanism: mismatch from nonlinearity and coarse-graining (label: sec:results:mechanism)
• QT §7 A classical analogue: staged objecthood in metastable Markov dynamics (label: sec:markov)
• NT §5.2 Arrow audit II: path-reversal KL and ``no fake arrows'' (label: tab:dpi)