Chapter 9: The lights of the aurora

On the night of 2 September 1859, the dark sky over Europe and North America was suddenly full of light. The light did not come from the sun or the moon – and it had a strange colour. The light moved across the sky, coming and going, like clouds in a strong wind. In the United States, a man in Boston was using the telegraph to speak to a man in Portland, 160 kilometres away. They both turned off the electricity for the telegraph, but they could still speak to each other for the next two hours. The electricity was coming from the light in the sky. How was this possible? And what was this light in the sky?

The light is called the aurora. Usually you can see it only at the very north of the earth, where it is

called the aurora borealis or Northern Lights, or at the very south, where it is the aurora australis or Southern Lights. But in 1859, something happened in the sun – a very large storm – and it moved the aurora across the middle of the earth.

We do not think that this ever happened before 1859, and we know that it has not happened since then.

The light of the aurora does not come every night. It comes because of storms 150 million kilometres away, in the sun. And the best times to see the light of the aurora are around the equinoxes, in March and September. Most often, the aurora is green, but it can be blue, or red, or any colour between. Sometimes the light is still, like the lights of a town far away; sometimes the

light moves, dancing in the sky.

But why does the aurora happen? And why can we only see it at the top or bottom of the earth? The aurora is made by something called the ‘solar wind’ (wind from the sun). We cannot see this wind, or touch it. It is a wind of particles that travel away from the sun all the time at about 400 kilometres a second.

Most of the particles never touch the earth. The earth has a kind of ‘wall’ around it that defends it against these particles. This wall is called the earth’s magnetic field, and it pushes the particles away on either side. It is like water going to each

side of a large stone in a river. But the earth’s magnetic field has two ‘windows’ in it: the magnetic north, and the magnetic south. At these places, the earth’s magnetic field turns down into the earth. And some of the particles from the solar wind come through these magnetic ‘windows’. These solar particles crash into the particles that are already in our sky. And when this happens, we see the beautiful lines or clouds of light of the aurora.

Where can you see the aurora? Alaska is a good place to see the aurora borealis, and you can also go to places like Iceland, Siberia, the north of Greenland, Norway, Sweden, and Scotland. To see the aurora australis, go to the south of Australia, Tasmania, or New Zealand.

The aurora australis from above the earth

People travel thousands of kilometres to see the aurora, and they can never be sure that it will happen. But people who do see it say that they will never forget it. So if you are ready to wait in the cold, and if you are lucky, perhaps you too will see the aurora when it dances across the sky.