Aurora Borealis, Australis
The Northern and Southern Polar Lights
The long nights mean that this is the peak season for an extraordinary spectacle. For thousands of years, people have marvelled at the spectacular lights that sometimes appear in the night sky and have wondered what on earth they could possibly mean.
The Northern Lights
The Vikings believed them to be the reflections of dead Maidens. The Cree native Americans call them the dance of the spirits, and, in Europe in the Middle Ages, they believed the lights meant that God was angry.
But the truth is actually even more extraordinary. This celestial light show or Aurora as it's known, is the front line in the battle between the Sun and the Earth's atmosphere. Every second, the sun blasts out a million tons of radioactive particles and the Earth is in the firing line.
The sun emits a continuous floor of charged particles, known as the solar wind. This streams outward, in a wash of radiation. But when it reaches the Earth, it encounters a barrier. The Earth's magnetic field deflects the particles and funnels them towards the poles. Here, they collide with atoms of nitrogen and oxygen in the atmosphere. These collisions emit energy in the form of light, giving us the Aurora.
From the International Space Station, you get a better sense of the awesome scale of the Aurora. We don't often think of it this way, but the Aurora is graphic evidence that we live inside the atmosphere of the sun. This is the Sun's atmosphere colliding with the Earth's atmosphere.
So our orbit, close to the sun is full of risk. But it's also vital for our survival.