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Kyre comments on Musk, Mars and x-risk - Less Wrong Discussion

10 Post author: Kawoomba 23 November 2012 08:32PM

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Comment author: gwern 25 November 2012 06:38:15PM 5 points [-]

By the same logic,

Supernova, GRB : probably ? Unlike impactors, a supernova or GRB would affect both Earth and Mars. However, if the major impact on Earth is deaths by radiation of exposed people and destruction of agriculture by destruction of the ozone layer, then Mars should be much more resilient, since settlements have to be more radiation hardened anyway, and the agriculture would be under glass or under ground.

Is not a good addition. The Mars-hardened facilities will be hardened only for Mars conditions (unless it's extremely easy to harden against any level of radiation?) in order to cut colonization costs from 'mindbogglingly expensive and equivalent to decades of world GDP' to something more reasonable like 'decade of world GDP'. So given a supernova, they will have to upgrade their facilities anyway and they are worse positioned than anyone on Earth: no ozone layer, no atmosphere in general, small resource & industrial base, etc. Any defense against supernova on Mars could be better done on Earth.

Comment author: Kyre 26 November 2012 05:09:31AM 2 points [-]

Good point. Mars would only be better off if the colonies over-engineered their radiation protection. Otherwise anything that gets through Earth's natural protection would probably get through Martian settlements designed to give the same level of protection. It might be relatively cheap to over-engineer (e.g. digging in an extra meter), but it might not.

Comment author: gwern 26 November 2012 04:25:36PM 0 points [-]

It might be relatively cheap to over-engineer (e.g. digging in an extra meter), but it might not.

FWIW, while researching my Moore's law essay, I found materials claiming that underground construction was more expensive but paid for itself via better heating/cooling. But that was for shallow cut-and-scrape constructions and I suspect 1 meter wouldn't take care of supernova radiation.

Comment author: shminux 26 November 2012 05:32:24PM *  4 points [-]

I suspect 1 meter wouldn't take care of supernova radiation.

As far as I understand the issue, the danger is mainly from the temporary ozone layer depletion, with the resulting solar UV rays doing most of the damage, and not from any kind of direct supernova radiation. And UV is not hard to shield from.

Comment author: gwern 26 November 2012 06:15:06PM 3 points [-]

Hm, so you're right: http://en.wikipedia.org/wiki/Near-Earth_supernova#Effects_on_Earth In that case, it doesn't sound like that much of a direct threat at all: we can use cheap underground or UV-glass-filtering greenhouses to grow our food. A disaster, but not really an existential threat.