Is the Roman Pantheon a colossal sundial?
The image of the great circle illuminated by the sun that we see inside the Pantheon in Rome is a fascinating spectacle, particularly in summer when it falls on the floor and its great brightness contrasts with the faint light of the place. Some years ago was on sale near the entrance a small book in which, together with the history of the monument, the use of it as sundial was described. Nevertheless I have many doubts that the Roman architects wanted to create also a great sundial when they planned the Pantheon. The hole in the dome (called oculos) had, in my opinion, only the purpose to illuminate the great place in which, because of the enormous thickness of the walls, they could not create windows. Some number. The Pantheon is formed from a cylinder that has an height equal to the radius, surmounted by an half sphere. Since the radius is = 21.72m (71.2") the oculos is at 43.44m of height (142.5"). Its diameter is equal to 8.92m (29.3"), approximately 1/5 of the diameter of the dome. The center of the circle of light falls on the line between floor and walls at noon on May 1st and on August 10th and falls completely on the floor only between May 21th and July 22th (around) On summer solstice the center abandons the floor around at 1.5hours after noon. In the other periods of the year the bright ellipse falls on the wall. At noon on the equinoxes the center is at 19.2m of height and partly falls on the dome. >From October 1st to March 12th the light falls always on the inside surface of the dome, that is on the ceiling. A regard Gianni Ferrari P.S. Some image of Pantheon are in http://www.florense.it/Architettura_Mediterranea/Pantheon.asp#Rotonda_del_Pantheon http://commons.wikimedia.org/wiki/Pantheon_(Roma) See also in http://en.wikipedia.org/wiki/Pantheon,_Rome
--------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
