Anselmo et All,
I think the answer to your question is latitude
45 degrees.
At any place the sun is half a year above the
horizon.
This also means that the sum of the hours that a
north facing wall and a south facing wall catch the sun also is half a
year.
So we have to look for the latitude where a north
facing dial catches the smallest amount of the sun ( or where a south facing
dial gets the highest amount of the sun ).
At the pole the sun shines at the north side for
50% as you said.
Going to lower latitudes this percentage
decreases to a minimum but than increases to the same amount of
50% again at the equator as you also said.
At first glance I should answer that minimum than
will be just between at latitude 45 degrees.
If this symmetry is true this also would mean
that at latitude X and at latitude 90 - X the number of hours of sunshine on a
north facing dial is equal. ( and the numbers of hours of sunshine on the
south dial also is equal )
And indeed this is true.
Have a look at the attached pictures of a north
facing dial at 23.5 and at 66.5 degrees.
You may see that the amount of sunshine is equal
for both latitudes.
And this equality is present for any couple of
latitude X and 90 -X.
So I think that the answer to your question
is 45 degrees.
Best wishes, Fer.
----- Original Message -----
Sent: Sunday, March 03, 2002 5:02
PM
Subject: Re: On northern vs. southern
dials
Hi Mike, hi diallists,
When I said a sundial in the North
Pole I meant a sundial, say, at 1 cm from it. There the
concept of North still makes sense and it is
obvious that there there are as many hours of
sunlight in the northern side than in the
southern side in the course of a year. And we can
make the same reasoning for a dial in the
Equator: there we have the same result, but with
a different distribution along the
days.
As for the 'not-50%+50%' question, you may
look at two things to realize that it is not like this
in all latitudes:
1st Take a glance at the lines in
a classical azimuthal sundial (you can make one with Sonne
program).
2nd (and more convincing ;) just
ask how much does it cost a flat or a house oriented southwards
and another one oriented northwards... Where I
live the difference is no less than 30000 euros!
I do believe (David Pratten said something like
this) that the bigger differences occur close to the the
Arctic Circles and to the Tropical Circles, but
I can't prove it. I suppose that in the end I'll have to apply brute
force but I think as well there must be a
better way to prove it.
Anselmo
----- Original Message -----
Sent: Sunday, March 03, 2002 1:54
PM
Subject: RE: On northern vs. southern
dials
Thinking about this question a little more - during the course of a
complete year, doesn't every point on Earth get 50% light and 50%
dark?
So, the further North (or South) you go, the more of the 50% shines
on the South (or North) facing wall.
So the North (or South) pole is the place to go to get the
maximum light shining on the South (or North) facing
wall.
