A mysterious spiraling blue light illuminated the night skies over Europe on Monday ... shows the glowing light spinning across the sky in what many social media commentators likened to a spiral ...

The difference between how light behaves on Earth and how it travels in the emptiness of space, explains the beautiful blue skies and the vast darkness of space. Why is the sky blue in colour?

0:36 Glowing spiral floats through U.K. night sky People across Europe witnessed a mysterious glowing blue spiral in the night sky this week, and scientists say they think they know what caused ...