Hi John and dialists all, Well, people living in mountainous country often tell time by the shadows of the various prominences and ridges. We are talking thousands of feet at the least here.
Even the moon's shadow moving across the earth tells some kind of time, and that is a far distance indeed. Perhaps if the question is restated in terms of dials that are totally constructed by human agency for the sole purpose of sundials we could come to a better answer. In this case we couldn't include the Kitt Peak Dial. In terms of the use of the shadows of fortuitous objects to tell solar time, I don't think we can name the largest! I don't believe we can go on the basis of the rate of movement of the shadow in linear terms at noon as a good measure of size, since there are projecting solar telescopes that have extreme rates of shadow movement, other multireflecting devices using non planar surfaces that also have very fast solar shadow movement. Some of these fast moving sundials use the reflected light as well, so we would have to include direct light and shadow movement as a measure. The shadow is, as I understand it, is kind of like a wet finger in the wind and tells us in combination with the gnomon and dial face the direction of the vast field of the sun's rays. As a result, perhaps the best measure would be the longest optical lever, but still some may be thousands of miles if we use the shadows of orbiting satellites to tell time. After all that, I believe I would go with the measure of the largest, calibrated, dial face area as the best way to compare the kind of dials we are dealing with. Does this make the contest easier? Edley [EMAIL PROTECTED] -
