The Intake converts ~8 billion people into life-support substrate powered off the Sahara. Could that actually work? Set the parameters and find out where the real ceiling is — it isn't the one most people expect.
Power draw = (biological brains × 20 W × acceleration × support-overhead) + (digitized minds × ~50 W each). That total is compared to the Sahara's average electrical capacity.
The Sahara is ~9.2 million km² and receives ~2,500 kWh/m²/yr. At a conservative ~10% end-to-end system efficiency that is ~25 W/m² of continuous electrical output, so the full desert is ≈ 230 TW. As a sanity check, ~1.2% of that (~2.8 TW) matches world average electricity demand — the widely-cited "cover 1.2% of the Sahara to power the world" figure.
Even with a generous life-support overhead and accelerated metabolism, the preserved population draws a fraction of a percent of the Sahara. The canon's "sufficient, with margin" is correct. The binding constraint is biology: a brain runs at ~20 W and doubling its subjective speed roughly doubles its heat (≈40 W at 2×, ≈100 W at 5×) inside ~1.35 kg of tissue — and neural firing, synaptic delay, the binding rhythm of consciousness, and neurotransmitter depletion all cap how fast tissue can be driven. That is what the augmentation ladder shows: you only reach high acceleration by progressively replacing the biology — at which point the open question stops being power and becomes whether it is still the same mind.
This is the ancient Greek puzzle applied to neuroscience: if you replace the planks of a ship one by one, at what point is it no longer the original ship? The augmentation ladder poses the same question in biological terms. Replace a synapse with a faster photonic equivalent — is the mind still continuous? Replace the sensory pathways — still the same person experiencing them? Replace the cortex while keeping the limbic system — still you? There is no known threshold at which the answer clearly switches from yes to no. The ETI's staged, conservative dilation schedule — the 50× limit in New Tripoli, the doubling schedule across series — reads, in retrospect, as a system that doesn't have a clean answer either. They are watching to see where the continuity breaks.
Support-overhead (×3) and per-digital-mind wattage (~50 W) are deliberate round estimates, flagged ✦ speculative. The 90/10 split, Saharan siting, and ~8.1B population are ◆ canon.
Pairs with the Time Dilation Instrument — this tool sets the realistic acceleration ceiling that the dilation tool then runs with. See Cognitive Husbandry.md, "Technical Feasibility: Brain in a Vat."
Further reading: Attwell, D., & Laughlin, S.B. (2001). "An Energy Budget for Signaling in the Grey Matter of the Brain." Journal of Cerebral Blood Flow & Metabolism, 21(10), 1133–1145 — the canonical paper on the brain's ~20 W energy budget and why it cannot simply be scaled up without thermal consequences. Jacoboni, C., et al. (2022, in IRDS 2022). "International Roadmap for Devices and Systems" — sets the public technology projection baseline for digital substrate efficiency, grounding the "digital mind" power estimate.