Wait a moment... The amount of sunlight is the same in spring and summer and the same in autumn and winter. Temperature is not the same thing as sunlight.
From what I can gather, they factored temperature in because of the average amount of clothing people wear. More exposed skin means less time in the sun needed.
I wonder about both sons living above the Arctic Circle. I tend to be opposed to vitamin supplements, but do wonder if extreme situations warrant them.
the solar energy striking the square inch of earth (or skin) varies over the year.
The variance is small but measurable; it relates to the angle-of-incidence of the sunlight. (The angle is much better in summertime than wintertime, due to the Sun's apparent movement towards the North sky in the summertime.)
However, I suspect the variance in recommended times is split between this answer and BS's. Both factors are in play.
On another front, my hometown (Metro Detroit) is at 42.3 N latitude. Is that far enough from the line to be worrisome? Maybe some more detailed research is in order.
Wait a moment... The amount of sunlight is the same in spring and summer and the same in autumn and winter. Temperature is not the same thing as sunlight.
ReplyDeleteFrom what I can gather, they factored temperature in because of the average amount of clothing people wear. More exposed skin means less time in the sun needed.
DeleteI wonder about both sons living above the Arctic Circle. I tend to be opposed to vitamin supplements, but do wonder if extreme situations warrant them.
ReplyDeleteOTOH, they both eat a lot of fish these days.
@Joseph,
ReplyDeletethe solar energy striking the square inch of earth (or skin) varies over the year.
The variance is small but measurable; it relates to the angle-of-incidence of the sunlight. (The angle is much better in summertime than wintertime, due to the Sun's apparent movement towards the North sky in the summertime.)
However, I suspect the variance in recommended times is split between this answer and BS's. Both factors are in play.
On another front, my hometown (Metro Detroit) is at 42.3 N latitude. Is that far enough from the line to be worrisome? Maybe some more detailed research is in order.