The Greatest Show Off Earth

Posted by Dave at 06:40 PM, November 17, 2004

The other morning I was on the 4 till 8 watch, and thinking about the Northern Lights. Above the horizon, hints of pink and red were beginning to appear from a dark cloud. The colours turned to a deep red with a sudden searchlight of green sweeping in an arc across the whole sky.

Just as quickly, the lights were gone. I started thinking about what the first sailors - or even the first people - living in the far North must have thought about the Northern Lights. All of a sudden a giant ethereal cobweb appeared, covering all corners of the sky - north, south, east and west. There was a ghostly apparition in the centre of the sky, directly above the ship - swirling and dancing like an angel at work.

I realised then that my thoughts were also first thoughts, this was the first time I had seen this phenomenon.

- Ed

This wasn't my first time seeing the Northern Lights - but it was definitely my best experience of it. Out in the middle of the Atlantic Ocean, nothing around in the dark sea but white horses on the crest of the massive swells - and the greatest show off earth playing 100km or so above us. The Northern Lights - or the Aurora Borealis - is usually seen in the northern Polar Regions. We weren't that far north - south of Iceland, and west of the Scottish Highlands, but during the last week it could be seen as far south as Dublin. There's never two auroae the same - there's always a variety of arcs, bands, rays, patches, veils, appearing in different colours, different sequences and sizes.

Believe it or not, the sun fuels the Northern Lights - yes, I know there's no sun at night (unless it's summer in the far north!). The sun is always spitting out charged particles from thermonuclear reactions - protons, electrons and ions, which form the 'Solar Wind', which sweeps across space at 400 km per second, colliding with planets, moons, and anything else that gets in its way. As the particles reach the Earth's magnetic field (magnetosphere), they are twisted into spirals along the field, while the magnetosphere itself is 'squashed' towards the Earth. The Earth tries to hold the magnetosphere in place, while the Solar Wind tries to stretch it out. At the Earth's poles, the magnetic field converges to create a funnel effect, through which the Solar Wind is channelled. The Solar Wind collides with oxygen and nitrogen in the atmosphere, exciting the electrons to the point where they emit light - the different colours depend on the gas that collides with the solar wind.

Our sun provides the "fuel" needed to produce the Aurora. The Sun continuously emits charged particles, which are the by-products of thermonuclear reactions occurring inside the Sun. These charged particles, such as protons, electrons, and ions, form the Solar Wind, which travels through space away from the sun at speeds of about 400 km/s (about a million miles per hour), and collides with planets, moons, comets, etc. Results of these collisions can sometimes be quite dramatic. For example, the Solar Wind causes comets' tails to point away from the Sun, and the collision of the Solar Wind with the Earth's atmosphere causes the Aurora.

So much for what the Northern Lights 'really' are. It's an eerie experience seeing the lights out here, with nothing around us but hundreds of miles of Atlantic Ocean around us. The patterns and colours unfold randomly like a Rorschach animation. Still, my mind keeps trying to make sense of it, as if there could be some design, some deliberate sequence to the performance. It's a very human reaction - trying to make sense of the incredible.

- Dave