well said Jack, flat Earth and similar are unlikely :-)
Fabio Fabio Savian [email protected] www.nonvedolora.eu Paderno Dugnano, Milano, Italy 45° 34' 10'' N, 9° 10' 9'' E, GMT+1 (DST +2) From: Jack Aubert Sent: Thursday, September 17, 2015 12:21 AM To: 'Brent' ; 'sundial' Subject: RE: due east photos Maybe it helps to bear in mind that while all triangles on a plane surfaces contain 180 degrees, this is not true on a sphere. You cannot make a triangle on a plane surface that has two 90 degree angles because the sides will never meet. On a sphere, however, a triangle can easily have two 90 degree angles. If one side is congruent with the equator then the two sides will meet at the pole. The angle a the pole depends on the length of the equatorial side. A triangle with three 90 degree angles will take up one eighth of the sphere’s surface. East, west, north and south are spherical directions, not straight line on a plane surface. Jack Aubert From: sundial [mailto:[email protected]] On Behalf Of Brent Sent: Tuesday, September 15, 2015 9:47 PM To: sundial Subject: due east photos I am having an off list discussion with Dave but I have a photo that you may find informative. I resized them for the list so I hope you can see the latitude lines. what you are seeing is my globe oriented on north south axis and correct angle for latitude. I have a ruler close to my location with the zero on a latitude line I am pointing the ruler due east, where the sun will rise on the equinox as it peaks over my horizon. As we look straight down you see a deviation from the latitude line of about 1" at 4" on the ruler. Just rough scale 4" = 4,000 miles so 1" equals 1,000 miles = 25% deviation. My horizon is about 50 miles from here so when I look at the sunrise on the equinox my latitude is actually about 12.5 miles north of that point on the horizon. So it's not an insignificant difference. brent -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -------------------------------------------------------------------------------- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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