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okay wait i also have a technical question about seveneves [mild spoilers ahead]. they go from [small number] of humans to [large number] of humans while staying in orbit for [long time]. where did the *carbon* to create the organic molecules in those humans come from???

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QC (in Berlin 7/29-???)

@QiaochuYuan

· May 15

ok i finished seveneves. i admire how much work went into thinking through the physics but the technocratic disdain for religion and spirituality throughout was incredibly grating. read olaf stapledon’s last and first men instead which handles similar themes but is from 1930 (!) twitter.com/QiaochuYuan/st…

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QC (in Berlin 7/29-???)

@QiaochuYuan

[more spoilers] afaicr no process described in the book introduces new carbon into the system with the possible exception of the black sludge from the comet? they say they grow algae to feed people but algae need CO2 to photosynthesize, that at best recycles carbon breathed out

6:33 AM · May 16, 2022Twitter Web App

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QC (in Berlin 7/29-???)

@QiaochuYuan

May 16

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@QiaochuYuan

without the sludge i think as their population grows the air gradually becomes depleted of CO2 and the algae stops growing. maybe the sludge fixes this but this is not ever explicitly stated anywhere and neal stephenson is a real stickler for detail elsewhere

QC (in Berlin 7/29-???)

@QiaochuYuan

May 16

"carbon" is partly standing for all the other different types of atoms you'd need too (e.g. also need hydrogen, oxygen, nitrogen...) but maybe this is actually even worse for trace minerals? those should be coming from soil and they had to make all their soil from scratch