15 September 2010
Click sundial to enlarge.
I received this sundial as a gift years ago, and I've lost the details, but I think it's a reproduction of a sundial designed by Thomas Jefferson for his garden at his estate of Monticello, Virginia.
Monticello is at Latitude 38° 0′ 37.01″ N
My reproduction is at 42° 23′ 30″ N
Sundials are latitude-specific, so if Jefferson did his trigonometry right (and he almost certainly did), this sundial only tells the correct time at Monticello's latitude.
Moving the same sundial substantially north or south will skew or distort the sundial's time-telling accuracy.
However, you can adjust for this by doing some more trigonometry and skewing the sundial's circular base up or down from its intended position parallel to the ground. If you get the off-parallel angle just right, the shadow cast by the gnomon will again tell the correct time.
I haven't skewed this sundial to correct for its new latitude, so, like Jefferson's at Monticello, it's parallel to the ground.
So what time is it REALLY?
2 Large Pizzas, 3 toppings of your choice. Show your work. In other words, you don't get pizzas just for saying:
II & XLIX/LX POST MERIDIEM
(and that's just a dummy value, it's probably wrong).