https://www.davidb.org/tags/thermodynamics/ Recent content in Thermodynamics on Brownian Motion Hugo en-us Sun, 19 Jul 2026 10:23:14 -0600 https://www.davidb.org/post/2026/astrophage-thermodynamics/ Sun, 19 Jul 2026 00:00:00 +0000 https://www.davidb.org/post/2026/astrophage-thermodynamics/ <p><em>Notes on why Andy Weir&rsquo;s astrophage (from</em> Project Hail Mary*) violates the second law of thermodynamics, prompted by watching Veritasium&rsquo;s <a href="https://www.youtube.com/watch?v=DxL2HoqLbyA">&ldquo;The Most Misunderstood Concept in Physics&rdquo;</a>.*</p> <h2 id="the-claim">The claim</h2> <p>In the book, astrophage feeds by absorbing heat directly — infrared/thermal energy from its surroundings (a star&rsquo;s corona, or the dense atmosphere of Rocky&rsquo;s homeworld Erid) — and stores that energy in a compact, fully recoverable form (described as mass added to held neutrinos). Critically, it does this <strong>without radiating anything back out during absorption</strong>. It behaves as a perfect heat sink: energy goes in, nothing thermal comes out, and the energy can later be released as clean, usable energy (propulsion).</p>