Dr Sami Mikhail, a lecturer in Earth Sciences at the University of St Andrews, explains the Aurora Borealis.

On Sunday the 6th March 2016 the people of Scotland and northern England witnessed a beautiful natural phenomenon in the night sky, the Aurora Borealis. Living in Fife (colloquially known as the Kingdom of Fife) in Scotland, I was one of the lucky ones. For me, they brought to mind a particular quote from the Old Testament:

“And the bow shall be in the cloud; and I will look upon it, that I may remember the everlasting covenant between God and every living creature of all flesh that is upon the Earth” – Genesis 9:16.

This quote is about the colourful heavenly phenomenon known as a rainbow, which is simply (or not) the result of reflection, refraction and dispersion of light through water. Think of it like shining a white light through a crystal prism – i.e. the cover of Pink Floyd’s classic album, the Dark Side of the Moon. However, if the author(s) of Genesis understood science (geophysics to be precise), then he/she/they would have decided to cite the Aurora as proof of the “everlasting covenant between God and every living creature.” Because the Aurora is evidence that we are protected from harmful solar rays, and without this protection, we’d all die.

The Aurora is a magnificent and mystical-looking light show seen at night in the northern or southern hemisphere known as Aurora Borealis or Aurora Australis (or the Northern and Southern Lights.) I should state that contrary to the depth of colour commonly seen on Twitter, Facebook, and Google images, the Aurora Borealis isn’t a vivid spectacle, in fact they’re relatively faint to what is commonly assumed (note, this misconception can lead to disappointment, so rid yourself of this before viewing them.) The photos flying around the web showing the Aurora Borealis as an intense band of colour in the night sky are taken using long-exposure photography (or photo layering on some smartphones.) However, despite being relatively faint to the naked eye, they are undeniably beautiful, and invoke a sense of awe.

So what are they? Not surprisingly, every person who has seen them has pondered this question. Several ancient civilizations interpreted them as anything from spirits of the afterlife dancing in the sky, to harbingers of impending death, to literal gaps in the sky providing a glimpse into the heavens. Even famous (genius) revolutionaries like Benjamin Franklin had a go at explaining them – he thought they were something to do with the large volumes of snow and ice on the poles – note, this is wrong. The truth is actually provided by the etymology of their name. Aurora is named after the ancient Greek word for sunrise and Borealis is derived the ancient Greek word for wind (Boreas). Scientifically, one would say they are the result of solar wind interacting with Earth’s magnetosphere. Bear with me…