In 2010, researchers placed oat flakes at the positions of cities around Tokyo and watched a brainless slime mold build a network comparable to the real rail system. The organism was *Physarum polycephalum*, a single cell with no brain, neurons or central control. By reinforcing tubes that carried more flow and dismantling those that carried less, it produced efficient networks, solved shortest-path problems and inspired a mathematical model of adaptive network design. The mechanism is well understood. What remains open is how contractions stay coordinated across a large body with no nervous system directing them. ─────────────────────────────── IN THIS EPISODE— How *Physarum polycephalum* can behave like a network without a brain— The Tokyo experiment that compared slime mold with a real rail system— How flow and feedback produce optimization without an optimizer— Why coordination across the organism is still not fully explained SOURCESNature, 2000Science, 2010 ─────────────────────────────── Narration in this episode is AI-assisted. Research, writing, and editorial decisions are human. Reality Is Strange — real phenomena, verified, and stranger than they should be.

The Slime Mold That Rebuilt Tokyo’s Rail Network

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