tim-from-pa
Member
- Aug 4, 2005
- 4,716
- 435
This is a subject that I do not expect a lot of input or replies on considering it is a quirk of mine. I take interest in sundials. One of these days I'll find out what the "dial of Ahaz" really was in 2 Kings 20:8-11. There are so-called pictures on the internet what they thought it was. Basically it looked like a wall (i.e. a horizontal gnomon or pointer) that cast shadows onto steps as the elevation of the sun changed.
We now know that a gnomon must point parallel to the earth's axis, and a horizontal one only works on the equator (except if such a dial was inclined to your latitude, in which case it would no longer be "horizontal"). However, Israel, Egypt and such nations are about 30º North latitude and such a sundial would give crude time. So, if what they say is true, it would be feasible this is what they used.
I take interest in astronomy and mathematics. In my younger days (before computers) I could calculate reasonably well positions of planets (now I'm too lazy!!) For the sundial, it is really a "meridian marker" and there are simple trig calculations to make one. There is one other time correction to explain the variability of the sun, which is called the equation of time. Basically, this is due to the elliptical nature of the earth's orbit because it speeds up and slows down at various times and also its 23.5º tilt. For the mathematically inclined out there, it involves a simple application of Kepler's Law and Spherical trig. BTW, although I minored in mathematics, nobody taught me this. It came intuitively and I unknowingly "rediscovered" spherical trig on my own simply because I needed it to calculate astronomical positions (or..... as they say, necessity is the mother or invention)
We now know that a gnomon must point parallel to the earth's axis, and a horizontal one only works on the equator (except if such a dial was inclined to your latitude, in which case it would no longer be "horizontal"). However, Israel, Egypt and such nations are about 30º North latitude and such a sundial would give crude time. So, if what they say is true, it would be feasible this is what they used.
I take interest in astronomy and mathematics. In my younger days (before computers) I could calculate reasonably well positions of planets (now I'm too lazy!!) For the sundial, it is really a "meridian marker" and there are simple trig calculations to make one. There is one other time correction to explain the variability of the sun, which is called the equation of time. Basically, this is due to the elliptical nature of the earth's orbit because it speeds up and slows down at various times and also its 23.5º tilt. For the mathematically inclined out there, it involves a simple application of Kepler's Law and Spherical trig. BTW, although I minored in mathematics, nobody taught me this. It came intuitively and I unknowingly "rediscovered" spherical trig on my own simply because I needed it to calculate astronomical positions (or..... as they say, necessity is the mother or invention)