Hi Gianni, > In my opinion the Waugh's statement is correct if we think only > to the sundials in the North hemisphere (as Waugh did).
Yes, you (and Mr Waugh!) are quite right of course... > For this reason it seems to me a little " trick " to consider the > period of illumination of the South face in a sundial to the > ANTarctic polar circle :-) Yes, this is indeed one of my tricks! I like to think that every wall has TWO sides and the `wrong' side can be very interesting. North-facing dials are quite common but not many people realise that it is (theoretically) possible to have more than 12 hours of continuous sun on the same face of a wall. You just have to be in the right place! > For curiosity I send some approximate values... These are the figures I was thinking about, especially: > Latitude 66° 27' > Dawn 3h 27m > Start of the illumination 6h 43m > Length of the illumination 10h 33m It is the last figure that is responsible for my `trick'. Here the sun is on the `wrong' side for 24 - (10h 33m) = 13h 27m, well over 13 hours. Here is another `trick' concerned with the difference between the north and south hemispheres... If `summer' in northern latitudes is taken as the period between the March equinox and the September equinox and `summer' in southern latitudes is taken as the period between the September equinox and the March equinox then: a) Is summer longer in the north than in the south? or b) Is summer the same in the north as in the south? or c) Is summer shorter in the north than in the south? The correct answer is (a) but what is interesting is that the difference is OVER A WEEK. In Europe we have almost 8 more days a year where the sun is above the horizon for longer than it is below, than the poor people in Australia! Frank King [In Cambridge where it is raining heavily and all thoughts of sundials are purely theoretical at the moment :-(( ] -
