Image Northern Lights Through the centuries there have been many stories and myths about the northern lights. Our story takes us through all sides of the phenomenon, from superstition, culture, mysticism and religion to history and science. The Aurora Borealis, or Northern Lights, is a familiar sight on the night sky in Northern-Norway. It doesn't have to be cold or dark for the aurora to be active, but if we want to see it, the night has to be dark and clear - and that usually means it can get quite cold as well. Aurora Borealis is the international name for Northern Lights. It means "red dawn of the north". The Northern Lights originate from a zone high above the surface of the earth and can be seen at night in polar regions. The phenomenon appears when particles, rich in energy, are shot into the atmosphere, guided by the earth's magnetic field. The particles hit air molecules, for the most part consisting of oxygen and nitrogen. Between 100 and 300 kilometers from the surface, some of the energy of this collision is emitted as light. Image Facts about northern lights What is the aurora? The sun emits a stream of electrically charged particles (electrons, protons and helium nuclei). This stream is called the solar wind. The charged particles coming towards the Earth are affected by the Earth's magnetic field, which deflects the particles at an oval shaped area around each of the magnetic poles. Solar wind particles collide with the air molecules in the upper atmosphere. Northern lights never occur at altitudes below 80 kilometers and rarely over 500 kilometers. The average range for northern lights with maximum intensity is 110-200 kilometers; this varies from shape to shape. Image The sun The sun has been shining for 5 billion years. Light and heat radiation from the glowing gas sphere is a prerequisite for all life on Earth. The solar energy is created by nuclear fusion in its interior, where hydrogen is transformed into helium. Here, the temperature reaches 15 million degrees and the pressure is 250 billion times greater than at the Earth's surface. Sunspots are vortices created by the strong magnetic field on the sun's surface. Due to slightly lower temperature than their surroundings, they get a dark look. Sunspots are an expression of the processes that send charged particles into space, which can also be captured by Earth's magnetic field and create the northern lights. Image Aurora oval The aurora often appears and is most intense in an oval-shaped belt around the magnetic north pole – the auroral oval. In Norway, the belt follows the coast of northern Nordland, Troms and Finnmark. In these areas, you will be able to see the northern lights almost every clear, starry night in wintertime. In the Oslo area, the aurora can be observed a few times a month, while as far south as Berlin in Germany, it hardly appears once every year. Auroral outbreaks so far south have a connection with a high solar activity where the northern lights are pulled further south. By the Mediterranean Sea, the aurora is visible once or twice every century. The prevalence of northern lights in the northern hemisphere is shaped like an oval around the magnetic north pole. Here we can clearly see why Northern Norway is the "mild aurora country". Everywhere else, the oval covers cold and sparsely populated lands or seas. Colours and heights While the sun light contains every visible colour in combination, and appears to be white to our eyes, the northern lights contain only certain special colours. This is because the northern lights are created through light emission from atoms and ions in the atmosphere when they are struck by particles in the solar wind. The atmosphere consists almost entirely of nitrogen and oxygen and it is therefore up to the atomics’ special properties to determine the colour of the aurora. The illustration above shows how the aurora colours change depending on which atoms and ions that send them out. Aurora’s colours vary with height. The strong, green light appears in the area of approximately 120-180 kilometers. Above this, we find the red northern lights, while blue and violet mainly occurs below 120 kilometers. If there is a "storm" on the sun, the red lights appear between 90 and 100 kilometers above the Earth. Sometimes you can see a completely red aurora, particularly at low latitudes. Back in the day, this kind of aurora was often misunderstood as a large fire behind the horizon. Intensity Weak aurora has approximately the same brightness as the Milky Way. Milky Way, which is our galaxy, can be observed as a diffused, luminous track across the sky on starry nights. Medium strong auroras blend most of the stars. Strong northern lights can be compared to moonlight. That is when the northern light is much stronger than the light from all of the stars gathered. Auroral research today There has been a great progress in the research of the northern lights. While the researchers at the beginning of the century were preoccupied with the actual light distribution and aurora’s characteristics as the location, height, shape and colour, the main task today is to study the processes that cause the northern lights to occur in various forms and explain the rapid changes in time and space, which are so prominent. The researchers are particularly interested in the interaction between solar activity and Earth's near environment. In recent decades, increased attention on potential climate change has resulted in a higher interest for northern lights. The atmosphere in the altitude range where the aurora occurs is also important for the climate change. Image Image Mythology and superstition Throughout the thousands of years, a lot of stories and myths have been created about the phenomenon of the aurora. Therefore, the northern lights do not only connect to science and research, but also superstition, culture, mystery and religious plays. You can also find traces of the northern lights in literature and in art. At all times the aurora has been fascinating to people in the northern area and fueled their imagination and amazement.. The Greek philosopher Aristoteles apparently saw the northern lights in the year 344 B.C. He compares the aurora with flames from different light sources on earth. The oldest explanations of the Aurora can be found in Mediterranean countries and China. Because northern lights appear over the polar areas for the most part, the ancient people in these areas have at best seen very few auroral outbreaks. Prophet Ezekiel saw the view as a sign from God. "I had a vision. Behold, a whirlwind came from the north. It was a great cloud with flames of fire." The stories about the aurora have for the most part been connected to fear or awe and all the way until the Age of Enlightenment, the northern lights have been connected to the current perceptions of heaven and hell. The Norwegian Viking bards called the sky bridge between heaven and the earth "Bifrost". They may have thought about the northern lights. In this case, the northern lights have had their own god in the Norse mythology: Heimdall. Beliefs in Scandinavia linked northern lights to dead women in general, to the dead virgin souls especially. In China, the aurora was seen as a warning of impending births. When we talk to people about the aurora in Norway today, it becomes remarkably often told about when they were children, they waves white clothing at the play of lights and how they thought that the movements of the northern lights increased with the strength of their own waving. Illustration: These weave is called "Suitors" or "Daughters of the Northern Lights and is clearly inspired by Norse myths where the aurora was depicted as a female phenomenon. Image The King's Mirror The first realistic mention of the Aurora exists in the Norwegian work "Kongespeilet" ("King’s Mirror") from the 1200s. In the strong contrast to the usual European perceptions in the medieval times, Kongespeilet explained the Aurora as a natural phenomenon. The book’s unknown author presented theories like never before nearly 500 years later. Kongespeilet also gave the nature’s phenomenon a name – Norðrljós Centuries after Kongespeilet, Norway also became marked by dogma-filled and fantastic perceptions of the northern lights. Illustration: Vikingship under northern lights arch by Gerhard Munthe. Illustration to Snorre Sturlason's written saga about Norwegian kings. Image Preliminary research Aurora was seen over big parts of Europe in March 1716. The Aurora was also seen in London and it could be observed over the whole central-Europe. The well-known English astronomer and scientist Sir Edvard Halley was one of the people that were observing the northern lights. He started theories about the northern lights based on experience and comprehensive approach – to the detriment of speculation. From his own observations of the Aurora bending and his knowledge of the magnetic fields geometry, he concluded that these two phenomena had a near relation. This was the introduction to the modern aurora research that found a fertile ground in the freedom of thought, which the Age of Enlightenment gave opportunities for. In March 1716 Northern Lights were seen over large parts of Europe. This illustration er from Danzig in the northern parts of Poland. Image Kristian Birkeland Kristian Birkeland is one of the key people in the auroral research. Among other things, he created artificial aurora in a laboratory through the Terrella experiment. In 1896, he published a theory that would emerge as the most durable aurora theory into the twentieth century. Birkeland substantiated his theories with experiments in laboratories. Birkelands idea was that electric charged particles – cathode rays – stream out of the sunspots with such great speed that they get far into the atmosphere in the polar regions, led by Earth’s magnetic field. When the particles come down into the denser layers of air, they collide with gasses in the atmosphere and stop so that they light up the atmosphere gasses, which then glow like arches and beams.