[traceroute66]

> Cosmic background radiation is a thing

Indeed. But isn't it really only "a thing" for airline pilots, cabin crew and a few unfortunate people at ground level who happen to live/work high-altitude on mountains or somewhere lower down with the wrong kind of rocks ?

[_ph_]

Depends how you look at it. Cosmic radiation might not be extremely high level on the sea level, but it is a thing. So the total radiation dosis in a nuclear submarine might equal or even be less than on the surface.

Fun story: as part of my physics education we did an experiment on the cosmic radiation with a "radiation" telescope. That were 2 Geiger counters with a logic that only registered events which basically occured in both counters at the same time. That made the observation reasonably detectable and you could "see" the sun with this. This experiment was conducted indoors, just on the top floor of the building. We had about 1 event/second, our bodies would be getting a similar dosis all the time.

[beowulfey]

No, it is a gradient, with more exposure happening higher up. Radiation damage is considered “additive” over your lifetime. So if you are somewhere with less background radiation, you can receive more radiation from other sources and still be considered within “safe” limits. This is the basis for the policy mentioned.

[mlyle]

See https://news.ycombinator.com/item?id=29761595

[traceroute66]

Cool, thanks for that. I didn't realise XKCD actually posted serious stuff. ;-)

[trenchgun]

Also: https://what-if.xkcd.com/29/