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We have all seen sunny spots under trees, but have you noticed that the spots are round? This picture was taken on 22 October 2015 during an OSA meeting in Washington, D.C., USA. I have no clear memory of when I first noticed the shape of these spots, but it was probably during a partial solar eclipse in the 1970s. During the meeting, I did not find a single person who noticed the shape of the spots. However, one fellow participant could, with a little help, explain the spots when I showed him my photos:
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