On Mar 22, 4:20=A0pm, Aaron Denney <wno...@[EMAIL PROTECTED]
> wrote:
> On 2008-03-22, Keith F. Lynch <k...@[EMAIL PROTECTED]
> wrote:
>
> > Aaron Denney <wno...@[EMAIL PROTECTED]
> wrote:
> >> I hadn't realize eccentricity and inclination made such a difference.
> >> (15 minutes difference between mean solar time and apparent solar
> >> time). =A0It's still only half that required to get an offset of an
> >> hour, as Jette described. =A0I'd expect mountains to make a more
> >> practical difference in many places.
>
> > Sunrise and sunset are defined in terms of when the direction to the
> > sun is horizontal, not in terms of when the sun is visible.
=A0Otherwise=
> > in a deep narrow canyon, sunrise might be at 1150 and sunset at 1210.
> > So mountains have a negligible effect on sunrise and sunset times.
>
> Sure. =A0But they have a practical effect on when people get sunlight,
> which is supposedly the justification for DST.
Since the discovery of fire, people have been able to be up and active
when the sun and moon are not. Universally, they have tended to
extend their waking hours at the end of the day much more than at
the start of it - in fact, extending it to the point that they want to
sleep
past dawn on the following day.
During the summer at higher latitudes, the sun rises much earlier
than people want to. DST effectively ****fts a mostly 'wasted' hour
of daylight from the beginning of the day, when few people are up,
to the end, when far more want to be up and active.
In the winter, falling back to standard time means that the sun is
more likely to be up by the time most people are venturing outside.
That's the canonical arguement, and it makes sense to me. The
general idea is to align dawn more closely with when people start
their mornings, so less sunlit time is spent asleep.
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