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07/06/2018

A Sun Pillar over Norway - Astronomy picture of the day - 2018 June 7

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A Sun Pillar over Norway 
Image Credit: Thorleif Rødland
Explanation: Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light. Ice sometimes forms flat, six-sided shaped crystals as it falls from high-level cloudsAir resistance causes these crystals to lie nearly flat much of the time as they flutter to the ground. Sunlight reflects off crystals that are properly aligned, creating the sun-sun-pillar effect. In the featured picture taken last week, a sun-pillar reflects light from a Sun setting over FensfjordenNorway.

La grande épopée des ballons dirigeables - 2010 : le ballon captif de surveillance 101230-N-0020T-144

Ces aérostats sont apparus dès la fin du XIXe siècle. Dès leurs débuts, ils ont été utilisés à des fins militaires permettant l'observat...