Re: On northern vs. southern dials

[Anselmo P�rez Serrada]

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 ----- From: The Shaws To: sundial@rrz.uni-koeln.de 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.   Mike Shaw http://homepage.ntlworld.com/jmikeshaw/ N 53º 21' 24" W 03º 01' 47" Wirral, UK.