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Ball lightning is a rare phenomenon, typically appearing as a glowing sphere associated with thunderstorms. In 2008 one of the authors witnessed a blue ball-lightning object hover in front of a glass window that appeared to glow yellow. Calibrated quantitative fluorometry measurements of the window show that the glow was probably due to fluorescence caused by ionizing radiation (UV or possibly X rays)...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.