by Chris Peterson » Wed Jun 27, 2012 2:34 am
RJN wrote:Chris Peterson wrote:
You could actually do that with a white-light hologram.
That's an intriguing thought, Chris! I looked it up and someone has already published it though -- and patented it too. What escapes me just now, though, is how the degeneracy between two times of the year would be resolved. In other words, the Sun passes near one position on the sky twice during a year -- once before solstice (for example), and once after solstice. How would a "holodial" know which one of these two times is right?
That's an interesting question. You're thinking of the intersection point in the figure-8 of the analemma, no? I guess one approach would be to have a different place to stand, depending on the time of year. Effective, but not very elegant. Maybe some sort of passive kinematic element in the sundial/sculpture? I'll bet I could come up with a drive mechanism that that moves based on the daily cycling of temperature (like a ratchet with a bimetallic component), or maybe a tilt mechanism that depended on the typical temperature difference between the two times of year (which might get fooled occasionally). An interesting problem... now I might not sleep well tonight!
[quote="RJN"][quote="Chris Peterson"]
You could actually do that with a white-light hologram.[/quote]
That's an intriguing thought, Chris! I looked it up and someone has already published it though -- and patented it too. What escapes me just now, though, is how the degeneracy between two times of the year would be resolved. In other words, the Sun passes near one position on the sky twice during a year -- once before solstice (for example), and once after solstice. How would a "holodial" know which one of these two times is right?[/quote]
That's an interesting question. You're thinking of the intersection point in the figure-8 of the analemma, no? I guess one approach would be to have a different place to stand, depending on the time of year. Effective, but not very elegant. Maybe some sort of passive kinematic element in the sundial/sculpture? I'll bet I could come up with a drive mechanism that that moves based on the daily cycling of temperature (like a ratchet with a bimetallic component), or maybe a tilt mechanism that depended on the typical temperature difference between the two times of year (which might get fooled occasionally). An interesting problem... now I might not sleep well tonight!