As the Earth continues its path on its elliptical orbit around the Sun, high latitudes and higher mid-latitudes of the northern hemisphere are entering the midnight Sun season. If you go too far up north, the Sun never sets, but at a lower latitude, like southern Scandinavia, the Sun goes down just a few degrees under the horizon and lingers there for a few hours, gliding unnoticed from the northwest to the north-east.
This allows summer nights to remain in a constant twilight and it never gets dark enough to see the Milky Way or auroras for example. However, this situation, combined with some precise conditions, can give birth to one of the most intriguing and jaw-dropping shows on Earth: noctilucent clouds, author of this amazing time-lapse, Adrien Mauduit, explains.
While the Earth rotates far away from the Sun in the summer, its mesosphere gets cooler, allowing the formation of tiny ice particles. These particles form the highest clouds on our planet (82 km / 51 miles in the atmosphere) and wouldn't be visible if it wasn't for the bright nights!
See, the Sun being from 0 to 6 degrees under the horizon can, with the help of tropospheric clouds, emit rays that illuminate this ice layer, making the viewer's night sky glow electric blue, yellow and orange!
The Noctilucent cloud (NLC) season roughly starts at the end of May and finishes at the end of July in Denmark. You can gaze upon them when the weather is clear and potentially all night, most likely towards the north as the Sun follows its course under the horizon, backlighting the ice sheet.
As the 2017 NLC chasing season is about to kick off in Denmark, Adrien assembled some of his best shots of the 2016 season in a 4K time-lapse video as a tribute, and also teaser for the 2017 season, in hope to encourage more and more people to go out and experience these mind-boggling displays.
Video courtesy Adrien Mauduit
Featured image credit and caption: Adrien Mauduit