Caleb Scharf

The Ascent of Information

2021 003.54 SCH Tigard Library

I wanted to like this book. Rather than surprising, it was prolix and sometimes inaccurate.

• p37 planetwide rate of energy production, early 1800s 100 GW, year 2000 "in excess of a fearsome" 17 TW

  • Source https://ourworldindata.org/energy-production-consumption

    • Shows US power consumption decreasing by 1% in 2019; efficiency is improving, and digital controls help with tht
  • The earth absorbs and re-emits perhaps 1 kW/m2 solar, the sun-facing disk is about 1e14 m2, so the Earth radiates perhaps P=1e17 W at a top-of-stratosphere temperature of 200K or so. Emission is proportional to T^4, the derivative ΔT/ΔP ≈ T/4P ≈ 200/4E17 = 5E-16, so the heating from the "fearsome 17TW" is 5E-16*1.7E13 = 0.0085 Kelvins.
  • The actual "fearsome" question is how the energy is created; CO₂ from carbon combustion adds perhaps 3000x long term global heating compared to the technically-useful energy produced. Nuclear would be vastly safer, especially if the fuel was decommissioned weapon fissionables intentionally adulterated with U238 or Pu240.
  • hence ... fooey

• p37 47 GW for computation ... growing by 40% per year
  • Source: Nature 561 9/2018 163-166 doi:10.1038/d41586-01-06610-y

  • https://www.nature.com/articles/d41586-018-06610-y

  • shows graph from Anders implying data center energy (eyeball) 670 TWh/y (76 GW) in 2020, 2980 TWh/y (340 GW) in 2030, 4.44X growth, 16% growth per year.
  • the Green Growth graph shows ICT purchased half of corporate renewable energy (2GW) in 2016.
  • HOWEVER, the last actual datapoint was 2017, so everything after that is P.O.M.A. ... Pulled Out of My Ass
  • This text quote is more accurate: "Last year’s IEA report estimated that although data-centre workloads will shoot up — tripling 2014 levels by 2020 — efficiency gains mean that their electricity demand might sneak up only by 3%"
    • 3% in 6 years is 0.5% per year, not 16%.

Here's the cited Anders article: https://www.mdpi.com/2078-1547/6/1/117

• Figure one shows (expected) total consumer device power usage dropping from 1050 TWH/year in 2010 to 670 TWH/year in 2030, or 120 GW to 76 GW. Customers want battery life, not hand heaters.

What the graphs are actually measuring is the rapid globalization of internet access, combined with the rapid drop of energy per customer as electronic efficiency increases. Most of the world has some form of internet access in 2020; unless we train ants to use "smart" phones, we are approaching peak power, not exponential runaway.

• p234 ... the Great Dying 251 MYA (the Permian-Triassic extinction

  • Michael Benton, When Life Nearly Died: The Greatest Mass Extinction of All Time, 2003

  • Yadong Sun et al "Lethally Hot Temperatures During the Early Triassic Greenhouse", Science Oct 2012: p366-70, doi:10.1126/science.1224126

• p273 Dyson's over-the-top-proposal - two meter shell made from Jupiter, capturing all the Sun's energy.
  • "Search for artificial stellar sources of infrared radiation", Science June 1960, p1667-68. doi:10.1126/science.131.3414.1667
  • Dyson's argument was for Infrared SETI, not the notion that humanity will actually disassemble Jupiter to build a "spherical shell" massing 200 grams per square centimeter (2 tonnes per square meter) at twice Earth radius (3e11 meters).
  • The gravitational forces on that shell would be enormous, and crush strength "Einsteinian".
    • The orbital period at R = 2 Re ( ≈ 3e11m ) is 2√2 years ≈ 9e7 seconds, so the gravitational acceleration is
    • a = R * (2 π / T)² ≈ 1.5e-3 m/s².
  • The mass of the shell is M = 4 π R² × 2000 kg/m². The total distributed "rim" compression force is M/4 times a:
    • F = π R² × 2000 kg/m² * 1.5e-3 m/s²
  • The compression force is distributed over the circumference ( 2 π R ) times the thickness t (3 meters?) so the pressure is
    • P = F / 2 π R t = 1.5 ( R / t ) Pascals or 1.5e11 Pascals.
  • Jupiter is mostly hydrogen, a gas at 2 Re radius. If the hydrogen was (somehow) transmuted to perfect diamond, that would result in a compression strength of 470 GPa = 4.7e11 Pascals However, the density of diamond is 3500 kg/m³, so the shell thickness t would be only 0.57 meters, and the required compression strength climbs to 790 GPa.

  • It is amusing that these numbers are in the same ballpark ... but the bottom line is that a Stapledon-Dyson shell (his term, not "Dyson sphere") is just not strong enough that close to the Sun.

  • And even if it was - over those vast distances, the shell has effectively zero bending strength; restoring forces in a gravity field are negative, and it will rapidly buckle.
  • At 10 Re, the gravitational force is 25 times smaller than 2 Re, and thickness and the areal mass density is also 25 times smaller, so the compression pressure is 25 times smaller. Diamond would work ... but would still buckle.

  • A much thinner shell can be supported by actively adjusted light pressure.