[lorenzhs]

Cosmic background radiation is a thing and water is really good at blocking it, so it's not complete bullshit. Of course, without knowing what dose the GP received, it's impossible to say whether it's a comparable dose to what they would have received on the surface - but it's plausible.

[spfzero]

Not to mention radiation from the ground, which can be significant in some locations.

[doodlebugging]

(https://spaceweather.com/)

There is some good information about the relative exposure levels to cosmic radiation that one can expect to encounter on this site. They have been doing balloon launches and measuring in-flight levels for quite a while now.

[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/

[goodpoint]

The idea that radiation exposure can be "balanced out" is very sketchy. Reminds me of https://en.wikipedia.org/wiki/Risk_compensation

[ch4s3]

I think they just poorly explained that his exposure in the sub was lower than background radiation levels on the sea surface. You get more rads living in Colorado for a year than anyone would get working in a nuclear power plant for a year at sea level.