[Phys-L] globe sundials

[John Denker <jsd@av8n.com>]

Hi --

Maybe I'm the only one to not know about this, but I only recently found
out about globe sundials. They are very much niftier than the old fashioned
"gnomon plus flat plate" style, or even the fancier "equatorial" style.

They have been around for quite a while. Thomas Jefferson installed one
at Monticello. The one that's there now is a reproduction of a long-lost
original, installed in 2001, so if you visited before then don't blame
yourself for not noticing it.

https://www.academia.edu/110730076/Visualization_on_the_Day_Night_Year_Globe

It captures vastly more of the physics.

Among other things, in mid-summer you can use a globe sundial for 16 hours
a day in Bellingham, or 24 hours a day in Murmansk. That's in contrast to
old-style sundials, which are good for at most 12 hours a day
There are a couple of different versions: one with pins, and one with a
movable vane.

I don't know where to buy such a thing, but you could easily make one.