Search tools and guides ⌘K

V · Physics & hardware limits

Landauer principle

What it is

Erasing one bit of information dissipates at least kT·ln(2) joules of heat (≈ 3 × 10⁻²¹ J at room temperature).

Where it lives

Theoretical lower bound on computational energy. Why reversible computing is studied.

The key insight

Modern CPUs are ~10⁹ × above this limit. Cooling, not physics, is the immediate constraint — but the wall is real.

More in Physics & hardware limits

Speed of light c ≈ 3 × 10⁸ m/s in vacuum, ~2 × 10⁸ m/s in fibre (refractive index ~1.… Memory hierarchy L1 ≈ 1 ns, L2 ≈ 4 ns, L3 ≈ 12 ns, RAM ≈ 100 ns, NVMe ≈ 100 µs, network… Amdahl's law Speedup = 1 / (s + p/N), where s is the serial fraction. Maximum speed…

Across the foundations

VI Birthday attack Cryptographic foundations VI AEAD Cryptographic foundations VII P vs NP Computational complexity VII NP-completeness Computational complexity VII Approximation algorithms Computational complexity VII Reductions Computational complexity VIII Central Limit Theorem Statistics & inference VIII Hypothesis testing & p-values Statistics & inference

← All foundations