Maxwell's Demon (1867) sorts particles by speed, creating a temperature difference without work — seemingly violating the Second Law. Landauer (1961) resolved this: erasing the demon's memory costs kT·ln2 entropy per bit, restoring thermodynamics.
Parameters
N particles60
Speed threshold2.5
Noise0.05
Left Chamber (Cold)
Count:-
Mean speed:-
T_left
Right Chamber (Hot)
Count:-
Mean speed:-
T_right
Demon Memory
Bits used:0
Erasures:0
kT·ln2 cost:0
ΔS_total:0
Landauer's principle: Erasing 1 bit of information dissipates at least k_B T ln2 ≈ 2.9×10⁻²¹ J at room temperature. The demon acquires information (entropy decreases in box) but its memory fills up. When it erases to act again, the entropy cost ≥ the gained order. Total entropy of universe does not decrease. Szilard engine (1929): single-molecule engine produces k_B T ln2 work per cycle — exactly the erasure cost. This connection between information and thermodynamics underpins modern computing thermodynamics and limits on irreversible computation.