Aurora polaris: An unclear phenomenon

NTM CST 00008 900

In 1896, Birkeland started experimenting in his laboratory. Using a magnetized ball that was irradiated with cathode rays in an artificial space, he created luminous rings similar to the northern lights. Inspired by Birkeland, Størmer went to Bossekop in Alta, Finnmark in the winter of 1910 with his newly developed camera. The result of this expedition was the first photographs of the northern lights suitable for mathematical calculations. Through these experiments and observations, Birkeland and Størmer contributed to making the Northern Lights understandable, rooted in mathematical and scientific models.

Through artwork, science-historical objects, photographs and interactive installations, the exhibition conveys the history of research, but also tries to create an experience of the overwhelming and “magic” northern lights. Experiences that hits the stomach instead of the head. Parts of this exhibition were shown at the Istanbul Biennale in 2015.

This exhibition is part of the celebration of the Birkelandjubileet 13. - 16. juni 2017.

An unclear phenomenon

The Northern Lights have been a subject of study for centuries. What is this phenomenon? Is it possible to find a pattern?

The Northern Lights are a geographically determined, but variable phenomenon. It occurs more fre-quently in the Artic, but has been observed so far south in the northern hemisphere as Mumbai. At the same time, it varies with the strength of the Earth’s magnetic field. When the magnetic field is strong, the northern lights concentrate more closely on the magnetic pole, while a weaker field gives northern lights relatively far south. In addition, the magnetic pole moves. At the moment, the pole is close to Siberia.

A multitude of theories

There have been many proposed explanations of the Northern Lights. These explanation generally involve a link to other natural phenomena such as weather, tidal and solar activity. A few of the theories from the 19th century demonstrates the diversity in the study of the Northern Lights. According to these, the Northern Lights are:

  • Reflected sunlight from ice particles
  • Reflected sunlight from clouds
  • Sulphurous vapors
  • Nitrous gases
  • Burning of gases from putrefaction of animal and vegetable substances, ignited by falling stars
  • Luminous particles of the Earth’s atmosphere
  • Combustion of inflammable air
  • Magnetic effluvia
  • Luminuos magnetic particles
  • Meteoric dust ignited by friction in the atmosphere
  • Atmospheric circulation patterns
  • Electrified molecular circulation
  • Electric discharge between fine icy needles
  • Electric fluid in vacuum
  • Electrical discharge in the magnetic field
  • Electrical discharge between the Earth’s magnetic poles
  • Electric currents in aqueous vapor
  • Condensation of vapors carrying latent electric fluid

Towards clarity

During the 19th century, the observations of the Northern Lights became more systematic. When physicist Kristian Birkeland and mathematician Carl Størmer turned to studies of the Northern Lights, it was generally agreed that the Northern Lights frequency follows the socalled auroral zone, that intensity and frequency correspond to solar activity and that the Northern Lights and magnetic disturbances are connected to each other. However, the explanation of what caused the lights, was still disputed.

Self-luminous or reflective?

The main distinction between theories was whether the Northern Light is a luminous or reflective phenomenon. Polarization is a property acquired by the light from mirroring or refraction, and was discovered in 1808. In 1821 the French physicist Jean Baptiste Biot published studies of the Northern Lights that showed no traces of polarization. It pointed out that the Northern Lights had to be a luminous phenomenon and not, for example, reflections from the sun or volcanoes.

Northern light as electrical discharge

One explanation was that the Northern Lights were an electric discharge in the atmosphere. The Swedish physicist Erik Edlund suggested this in 1878 based on experiments with a magnetized sphere. When the sphere rotated, electrical power was formed in the connected wires. Edlund drew the parallel to the Earth as a a rotating magnet and assumed that a current flowed from the equator to the poles. As this flow would follow the magnetic field lines, there would be discharges in the Northern Lights area. The theory gained considerable support towards the late 1800s.

Northern lights and cathode rays

When the connection between the Northern Lights and sunspots was established in the late 1800s, cosmic theories gained support. The Danish physicist and meteorologist Adam Paulsen argued against the discharge theory claiming that the Northern Lights were caused by negatively charged rays called cathode rays in the atmosphere. Paulsen assumed that the air in the atmosphere was surrounded by a negative charge that radiated in all directions. These formed angles with magnetic field lines and created the Northern Lights.

The cathode rays also caught Birkelands attention. He assumed that the rays did not stem from the atmosphere itself, but from the sun. When these collided with particles in the Earth’s atmosphere, a light was created, the Northern Lights.

(NTM CST 00032) Bildetekst: Herman Fritz’ kart over utbredelsen av nordlys. Det var tidlig klart at nordlyset opptrer hyppigere mot nord. Utover 1800-tallet ble det foretatt systematiske undersøkelser, og i 1881 publiserte Fritz et kart over utbredelsen av nordlys i form av soner med et sannsynlig senter i den magnetiske polen som da var lokalisert til nordvestre hjørnet av Grønland. Foto: Norsk Teknisk Museum (NTM CST 00032)
Herman Fritz 'map of the spread of northern lights. It was soon clear that the northern lights occur more frequently to the north. During the 1800's, systematic investigations were carried out, and in 1881 Fritz published a map of the distribution of northern lights in the form of zones with a probable center in the magnetic pole, which was then located to the northwest of Greenland. Photo: Norsk Teknisk Museum (NTM CST 00032)

Fra Nordlysstasjonen i Kautokeino, 1882-1883. Foto: Norsk Teknisk Museum (NF.15006-033)

Kristian Birkeland (1867-1917)

Kristian Birkeland is considered the founder of modern physics in Norway. Birkeland had great drive, energy and ability to draw surprising conclusions.

At the same time, his impulsiveness and restlessness could come at the expense of the results.

Scientific nationalist

The research was Birkeland’s all. In 1895 he published a solution to James Clerk Maxwell’s general equations for electromagnetism, for which he gained international recognition. He chose instead to pursue the northern light, a marginal research field characterized by a multitude of theories. Perhaps it was Adam Paulson’s article about cathode rays and Fridtjof Nansen’s return from the Arctic Ocean that spurred his interest? Birkeland was an avid nationalist and wanted to contribute to Norway’s independence and self-esteem, also on a scientific level.

Birkeland’s own research,as well as the research field he founded in Norway through his research team and as an inspirator, established the Northern Lights as a fundamentally Norwegian research field in the period between 1890 and 1945.

In the service of science

Birkeland was a cornucopia of ideas. He registered over 50 patents, the most famous being the Birkeland-Eyde oven and the electric cannon. An economically profitable idea would ensure funding for research at a time when the country’s only university had limited resources for research in experimental physics. In 1905, Birkeland secured funding through the development of the electric arc furnace for fertilizer production and the foundation of Norsk Hydro (today Yara).

Det første røntgenfotografi tatt i Norge, 1896. Foto: Norsk Teknisk Museum (NTM C 4787)
The first x-ray photograph taken in Norway. Professor of Physiology Sophus Torup's hand photographed by Kristian Birkeland in February 1896. Exposure time: 5 min. Wilhelm von Røntgen (1845-1923) discovered in 1895 during experiments with electric expulsions in gases under low pressure rays that could crawl fabric and take photographs of, for example, the skeleton of living people. He called these x-rays. In March 1896, Birkeland demonstrated Røntgen's rays to the public at the Polytechnic Association and the Christiania Chamber of Commerce. Photo: Norsk Teknisk Museum (NTM C 4787)

Kristian Birkeland med guide og besetningen for observatoriet på Novaja Zemlja, Hans Riddervold, Johan Koren og Hans Thomas Schaanning, fotografert av Likovsky i Arkangelsk. Foto: Norsk Teknisk Museum (NTM C 26190)
Kristian Birkeland with the guide and crew of the observatory of Novaja Zemlja: Hans Riddervold, Johan Koren and Hans Thomas Schaanning, photographed by Likovsky in Arkhangelsk. Birkeland did several expeditions to the northern areas to study northern lights. Most extensive was the expedition in 1902-1903 with four stations in Iceland, Svalbard, Novaja Zemlja and Haldde at Bossekop. Photo: Norsk Teknisk Museum (NTM C 26190).

An Artificial Space

Birkeland assumed that the sunspots emits negatively charged rays called cathode rays. The Earth’s magnetic field draws the particles towards the High North. The particles collide with the gases in the atmosphere and in this collision light is ejected, producing the Northern Lights. In 1896, he published the results of his first experiments with cathode rays and magnetized spheres, terrellas. Until 1913, Birkeland used different chambers and terrellas for experiments resembling phenomena like northern lights, zodiacal light, the rings of Saturn and sunspots.

Controversial

Birkeland’s theory could not be proven, only circumstantial evidence as laboratory experiments and observations supported the theory. First in the 1960s with measurements from satellites was it possible to confirm the theory. Birkelands publications were controversial. Especially British researchers led by Sydney Chapman, rejected his theory and claimed that the northern lights were due to an electrical system in the upper atmosphere.

The universe

Terrella experiments were the core of Birkeland’s theory about the universe. In the lecture ”About the Creation of the Worth” held in 1913, he claimed that any solar system in development had electromagnetic forces of the same magnitude as the gravitational forces. He assumed that all stars have a greater negative electrical voltage in relation to the surrounding space that is maintained by radiance. A central body, such as the sun, extends particles that over time accumulate and form planets which circulate around it.

Birkeland’s theory was not the only one. Many physicists attempted in the early 1900s, before the theory of relativity and quantum physics became dominant, to establish new understanding of space with energy or electromagnetism as the main element.

Julius Plücker oppdaget i 1858 at dersom trykket i et katoderør blir veldig lavt, sendes det ut en negativt ladet stråle. Foto: Norsk Teknisk Museum
Notes from the experiments. In 1858, the German mathematician and physicist Julius Plücker discovered that when the pressure in a cathedral door becomes very low, a negative charge is transmitted. Plücker's discovery was central to a number of physical experiments around the turn of the century, such as northern theories, x-rays and the discovery of the electron.

Carl Størmer (1874-1957)

The mathematician Carl Størmer devoted his life to the study of the Northern Lights. In his main work The Polar Aurora, he describes his own career as a meeting between a pure mathematician and an avid amateur photographer.

Street Photographer

Størmer’s scientific interest was accompanied by a hungry eye. In the 1890s he walked in the streets of Karl Johan in Kristiania (Oslo) and Paris with a camera hidden under the jacket. Later, he used the photo interest to develop a method of photographing the northern lights that made it possible to make mathematical calculations based on the images.

Both films and lenses lacked the necessary sensitivity to photograph the northern lights at the beginning of the 20th century. In 1892 Otto Baschin and Martin Brendel took the first image of northern lights. With an exposure time of seven seconds, the image was too blurred for scientific analyses. Størmer’s solution was newly developed cameras specially adapted northern lights photography.

Accurate Testing

Størmer tested and evaluated the available lenses with dexterity. It was important not only to find the most light-sensitive plate or lens, but also the combination that best registered the color-range in the Northern Lights. He demonstrated the same stamina in his mathematical work. As a mathematician, he formulated and performed calculations of the theoretically possible trajectories of charged particles entering the Earth’s magnetic field, which he later controlled against calculations based on his photographic material.

Størmer på stranden ved Villa X i Drøbak. Foto: Norsk Teknisk Museum (NTM CST 00178)
Størmer on the beach at Villa X in Drøbak. Photo: Norsk Teknisk Museum (NTM CST 00178)

NTM CST 01142 web
Photo: Norsk Teknisk Museum (NTM CST 01142)

The Elevation of the Northern Lights

A critical question for all theories regarding the Northern Lights was where in the atmosphere the lights were produced. By observing the northern lights from two different locations at the same time, trigonometric calculations could be used to determine how high in the atmosphere the northern lights were situated. Several observers had used this method from the 1700s onwards. But the results varied widely and were inconclusive. This was because it was difficult to ensure that the observations were performed at the same time and that the measurements were made by the same part of the northern lights.

Photography and telephone

With the advent of the telephone it became possible to coordinate observations. During Birkeland’s northern lights expedition in 1899-1900, the two observers at the Haldde and Talvik peaks were connected by telephone which made it possible to ensure that the measurements were made at the same time.

In 1910 and 1913 Carl Størmer went on expeditions to Bossekop at Altafjorden. While connected by phone, he and assistant Bernt Johannes Birkeland photographed the northern lights from two different places at the same time. Later, Størmer made trigonometric calculations based on the photographs, and he estimated the height of the lights to between 100 km and 300 km above the ground surface.

Northern Lights Camera

With the help of the instrument maker Eugene Johannesen, Størmer prepared a prototype for a northern light camera and managed to make good images with an exposure time of only two seconds. To develop the camera further, he started a collaboration with physicist Ole Andreas Krogness. Together, they developed a method to take six images on the same negative plate, by making the lens moveable. It saved time since the plates did not have to be changed for each image. Between 1911 and 1935, more than 300 cameras were produced and sold to northern lights observers around the world. The Størmer-Krogness camera was the dominant camera in this field until the 1950s.

The Wire Model

In 1903 Kristian Birkeland challenged Størmer to quantify the movements of charged particles from the Sun to the Earth’s upper atmosphere. The major challenge was to describe mathematically the trajectories of the particles in a dipolar magnetic field similar to the Earth’s. He simplified the problem by investigating only the possible paths of individual charged particles, assuming they were unaffected by forces from other particles. In addition, he only performed calculations of negatively charged particles. These were extremely complex calculations, especially considering that an electron in motion is like a small electrical current deflected by magnetic fields.

Prohibited zones

The calculations not only contributed to an increased understanding of the northern lights. They also showed that certain charged particles in the Earth’s magnetic field can only move in specific areas around the Earth. In some areas they are captured and spin back and forth between the magnetic poles. Størmer’s calculations contributed to fundamental new knowledge in physics, and after 1925 it became apparent that they were useful not only in the field of northern light research. They also contributed greatly to the understanding of cosmic radiation in the area near the Earth, describing the fields known as Van Allen belts today.

Time-consuming project

In 1904 Størmer published his first paper Sur le mouvement d’un point matériel portant une charge d’électricité sous l’action d’un aimant élémentaire, and several more were published until 1916. Between 1916 and 1930 Størmer concentrated fully on auroral observations, and published no work about trajectories, but after 1930 he again turned his attention to calculating trajectories. By his own reckoning, Størmer and his assistants spent more than 20,000 hours on trajectory calculations between 1904 and 1916, and 13,000 hours after 1930.

To demonstrate his results, Størmer built elaborate models made out of copper wire, covered in white silk, and supported by metal ribs originally manufactured for umbrellas. We do not know exactly how many models were built, but it appears to have been more than 60. Størmer claimed that it took more than 1,000 hours for a graduate student to calculate a complete orbit and nearly 300 hours to build an accurate model. By translating the calculations into three-dimensional shapes, Størmer and his assistants were able to verify their results.

The Founding of a Research Field

In the first half of the 20th century research on northern lights developed in Norway. Both institutionally and knowledgeably, the profession had a strong Norwegian contribution until the 1950s.

The Birkeland-Bjerknes tradition

Norwegian geophysical science, meteorology, oceanography and Northern Lights studies, emerged as important disciplines around the turn of the century and were all based on classical physics. For an economy dominated by maritime commerce and fisheries, knowledge about weather conditions was crucial. The idea that the northern lights influenced the formation of clouds and other weather phenomena, proved central when the Norwegian parliament, Stortinget, granted money to Birkeland’s expeditions or the establishment of an observatory at Haldde - both costly projects.

Laboratory-based physics was expensive and had few immediate gains. The Norwegian initiatives were therefore directed towards field work such as expeditions and research vessels.

Research before satellites and computers

The collection of raw data and the subsequent analyses involved enormous work. As part of Birkeland’s second northern light expedition disturbances in the terrestrial magnetic field were analyzed. The material included Birkeland’s four observation posts, as well as submitted material from another 21 stations around the world. The introduction of computers and the space age evolving after WW2, changed the field and the Norwegian dominance was broken.

Størmer and Birkeland represents a larger collective with institutional anchoring in Oslo and Tromsø. Intuitionally the founding of Nordlysobservatoriet, Tromsø geophysical observatorium in 1928, proved important. The Norwegian research tradition was however part of an international research field. The results were published in French, German and English journals and monographs, and correspondence with other scientists and travel to leading European universities was essential for the establishment of the field.

Symbol of an Emerging Nation

Around 1900, the Northern Lights were established as one of the national symbols of Norway. Until the end of the 19th century, the Northern Lights were featured in travel descriptions and other reports about the northern areas alongside other nature and cultural conditions of the exotic north. The Northern Lights research contributed to its popularity and Birkeland was especially concerned with science’s heroic and nation-building aspects.

Nansen and the northern light

Fridtjof Nansen and the so-called Lysaker ring proved central to the rapidly growing interest for the Arctic. In illustrations and text, Nansen describes the Northern Lights and associates it with contemplation, the unknown and exploration. In 1897 Nansen writes:

”[I] was nailed to the spot the moment I got outside. There is the supernatural for you – the northern lights flashing in matchless power and beauty over the sky in all the colors of the rainbow! […] And now from the far-away western horizon a fiery serpent writhed itself up over the sky, shining brighter and brighter as it came.”, Farthest north

From studies to expeditions

Birkeland organized three expeditions to study northern lights and magnetism between 1897 and 1903. Where other publications on northern lights observations had titles such as ’report’ and ’study’, Birkeland described the observations in 1897, 1899-1900 and 1902-1903 as expeditions. As Birkeland provided the publications with descriptions of the harsh conditions the researchers had to work under, he wrote the Northern Lights research into the polar project and presented the scientist in battle with nature in the pursuit of knowledge.

 

NTM CST 00008 900
Størmer and Bernt Johannes Birkeland in Bossekop, 1913. The picture was taken by Anders Beer Wilse who happened to be in Bossekop to document the Sami market. In the picture, Størmer and Birkeland poses in polar raids with camera equipment and more. The archives of Størmer at the National Library contains a thank-you letter from Størmer to Alexander Nansen: "Can you tell me where Roald Amundsen sewed his eskimo suit and where he got his skins from. I was so excited about the suit that I borrowed for my Finnmarkstur this spring that I would like to have made my own. "Carl Størmer, 05.12.1910.

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