MTH Fiction Series · IV of V · Arthur C. Clarke — The City and the Stars

The Diaspar Choice

Clarke's 1956 novel renders the MTH decision point as a civilizational fork: Diaspar, an enclosed computational city whose citizens are reincarnated from memory banks for a billion years — and Lys, embodied, biological, mortal, and outward-looking. This calculator scores the fork: under what conditions does a rational civilization choose the city over the stars?

Fork Parameters · 1 Gyr horizon
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Reference Forks
Diaspar (Clarke)1 mW · 1% in · 75% out—
Lys (Clarke)100 W · 5% in · 10% out—
Earth 2026100 W · 30% in · 40% out—
Fork Verdict
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Inward / Outward score ratio (risk-adjusted experience per joule)
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Set parameters to calculate.
Diaspar
A single enclosed city, sustained by the Central Computer for a billion years. Citizens are stored as patterns in the memory banks and re-instantiated in rotation — effectively immortal, computationally maintained, and deliberately incurious about the universe outside. Clarke wrote the cleanest early picture of a civilization that chose permanent inward simulation, decades before anyone had the vocabulary of uploads or computronium.
Lys
The other survivor of humanity's retreat: a pastoral, telepathic, biological community that kept mortality and embodiment. Lys rejects Diaspar's bargain — it accepts death and risk in exchange for growth, children, and the open sky. The novel's protagonist, Alvin, is the first person in ten million years to want both. The fork between the two is the decision this calculator scores.
Fermi & MTH Connection
Diaspar answers the standard durability objection to the Macro Transcension Hypothesis — "could an inward civilization really persist?" — with a worked example: error-correcting memory banks, substrate maintenance, and a billion years of continuity. If the inward path is both cheaper per experience-year and safer per Gyr, silence is what rational civilizations look like from outside. See also the aestivation tool for the wait-then-compute variant.
ωCen as a Field of Diaspars

The score here is a labeled heuristic, not a physical model: each path earns experience-years per joule, multiplied by its probability of surviving a 1 Gyr horizon. The inward path wins on efficiency (a Diaspar-class citizen at ~1 mW costs five orders of magnitude less than a biological one) and usually on safety — an enclosed, quiet city presents no profile to whatever makes the outward path hazardous. The outward path wins only when expansion is both fast and safe, which is precisely the combination the Great Silence suggests is rare.

Omega Centauri is old enough — its stellar populations span roughly 11–14 Gyr — for the Diaspar bargain to have been offered thousands of times over. A cluster core dense with ancient stars is, under this reading, not an empty wilderness but a possible field of Diaspars: enclosed, thermodynamically frugal, billion-year-stable enclaves that long ago stopped signaling. The observational question is whether such enclaves leave any residue at all — compact waste-heat sources, or the STEM-compressed endpoints MTH predicts near the cluster's center of mass.

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