satchlj

satchlj’s Shortform

• satchlj 26 Oct 2024 15:50 UTC

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  on: [In­tu­itive self-mod­els] 1. Preliminaries

  Your brain has a giant space of possible generative models^[2] that map from underlying states of the world (e.g. “there’s a silhouette dancer with thus-and-such 3D shape spinning clockwise against a white background etc.”) to how the photoreceptor cells would send signals into the brain (“this part of my visual field is bright, that part is dark, etc.”)

  How do you argue that the models are really implemented backwards like this in the brain?

• satchlj 22 Oct 2024 19:12 UTC

  3 points

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  on: Arith­metic is an un­der­rated world-mod­el­ing technology

  Calculations on Hydroelectric Energy Storage

  For those interested in the numbers on pumped hydroelectric storage, we can get more energy by increasing ‘head’ or the distance that the weight falls, from 6 meters to up to 500 meters for some of the largest projects (and we could in theory go bigger).

  Let’s pick a more reasonable number like 60 meters:

  MASS/​house = 15 kWh/​house /​ (9.8 m/​s² × 60 m) = 91,836 kg/​house = 91 m^3/​house

  Let’s say we have a dam with ~20 meters of water level fluctuation (drawdown). Then that’s 5 m^2 per house of surface area.

  As a sanity check, Bath County Pumped Storage Station in VA stores about 24000 MWh/​ 30 KWh/​house = 800,000 houses worth of energy.

  800,000 houses * 5 m^2 = 4 km^2

  The Bath County reservoir is about 1km^2 so we’re in the right range here (the reservoir has a little more drawdown and a way bigger head).

• satchlj 12 Oct 2024 12:54 UTC

  1 point

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  on: Ed­in­burgh Scot­land—ACX Mee­tups Every­where Fall 2024

  We’re going to be at Söderberg The Meadows; although the rain has stopped the world is still soaking wet.