The circadian thing is interesting! There was a long-held datum based on experiments that isolated people from all external time-cues and let them just "free-run" that set the average natural human cycle at about 25 hours, and that's also what a lot of completely blind people end up on.... But if you instead stick people on an artificial isolated rhythm (like a 28-hour day) and measure things like body temperature instead of just sleep times, you get a cycle very close to 24 for nearly everyone, even as it gets farther off their sleep/light cycles.
Which makes me wonder if they're measuring two different things- if sleep cycle naturally lags our other circadian cycles for some reason. I haven't found anything where they tested other circadian cycles on people who were freerunning on sleep, or specifically tested whether those other cycles are as effected by light exposure as sleep is.
I used to think I had a longer-than-24 sleep cycle, but if I'm careful about artificial light exposure, that effect seems to mostly go away (though that might also be related to getting older.)
Anyway, yeah, it's interesting to think about at what point off a 24-hour day humans would just give up on working with planetary day!
Some NASA teams that work closely with the rovers have run long-term on Mars time 24-hours-and-almost-forty-minutes, and it has not worked very well, but also they seem to have treated it more like shift work than actually adapting to a different day.
I also have to wonder if people with off-kilter sleep cycles would be disproportionately likely to volunteer for that kind of mission! The only thing is that a seriously off-kilter sleep cycle tends to make it a lot harder to be the kind of person who wins slots on space missions....
no subject
Which makes me wonder if they're measuring two different things- if sleep cycle naturally lags our other circadian cycles for some reason. I haven't found anything where they tested other circadian cycles on people who were freerunning on sleep, or specifically tested whether those other cycles are as effected by light exposure as sleep is.
I used to think I had a longer-than-24 sleep cycle, but if I'm careful about artificial light exposure, that effect seems to mostly go away (though that might also be related to getting older.)
Anyway, yeah, it's interesting to think about at what point off a 24-hour day humans would just give up on working with planetary day!
Some NASA teams that work closely with the rovers have run long-term on Mars time 24-hours-and-almost-forty-minutes, and it has not worked very well, but also they seem to have treated it more like shift work than actually adapting to a different day.
I also have to wonder if people with off-kilter sleep cycles would be disproportionately likely to volunteer for that kind of mission! The only thing is that a seriously off-kilter sleep cycle tends to make it a lot harder to be the kind of person who wins slots on space missions....