The picture, taken near Ajo, Arizona is a multiple exposure, each shot taken ten days apart, at 8:30 AM for a year. The sun's seasonal shift forms this figure 8, known as the analemma. Because of this effect, sundials can run ahead of clock time by as much as 16 mins 33 secs or fall behind by as much as 14 mins 6 secs.
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When I saw this picture, it reminded me of an elderly gentleman named L. Gordon Plummer. He was retired, but volunteered time to come into my sixth grade class and teach us physics once per week. He'd teach us interesting things like basic concepts in relativity and quantum mechanics, or about hyper-cubes (four-dimensional objects). He invented a sundial that is always correct, by incorporating an analemma-shaped object into the design. It's still standing (I think) in Balboa Park in San Diego. I'm sure he's passed on long ago now. He was an interesting person, one that made an impact on me.
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