The Life and Death of Planet Earth

Peter D. Ward and Donald Brownlee 2002 0805067817

booknotes

• I learned a lot from Ward&Brownlee's Rare Earth (2000), and Ward's Under a Green Sky (2007)

  • I didn't see "Life and Death" until 10 years after publication, hence much of the contents are old news
• Subject: Long term climate change in a world without geoengineering
• Reiterates that we live at a time suited for intelligence, rare in Earth's very long history
• More glaciations due

  • Root cause, weathering of Himalayas and abnormally low CO₂

  • Previously warmer, wetter
• Future heating due to sun heating
  • Solar heating because helium hotter at same pressure and density
  • Denser hotter core means faster fusion
  • Sun expansion at 7GY from now (not 10 as I remembered) oopsie
• Earth in old age - mostly because sun heating limits life span

• Claims animal life possible only ± 500MY from now

• Dismisses space technology
  • yes, rockets are expensive, book assumes forever
  • Moving to Mars
    • Who needs another (too small) planet?
  • Moving earth with repeated cometary encounters
    • 100 km diameter comet, go to mars orbit, would lose moon
    • 2001 Don Korycanscky, Gregory Laughlin, Fred Adams

      • http://arxiv.org/abs/astro-ph/0102126 Feb 2001

      • 300 AU semimajor axis, 1e18 kg every 6000 years, 1 million times
      • my note: how about ten 500 tonne objects a second? Or 1 million 5 kg objects a second?
• My heating recovery calculations:

  • Solar Shielding/reflector at 0.95 A.U., 10 grams per meter squared, 3e16 m², 3e14kg

  • 12 km/s delta V, 20% efficiency, 100 year mass replacement rate, --> 36 Terawatts

    • 1e-13 of solar output