Hessdalen light
Encyclopedia
The Hessdalen Light is unexplained light (a type of will-o'-the-wisp
Will-o'-the-wisp
A will-o'-the-wisp or ignis fatuus , also called a "will-o'-wisp", "jack-o'-lantern" , "hinkypunk", "corpse candle", "ghost-light", "spook-light", "fairy light", "friar's lantern", "hobby lantern", "ghost orb", or simply "wisp", is a ghostly light or lights sometimes seen at night or twilight over...

) usually seen in the Hessdalen
Hessdalen
Hessdalen is a village and a long valley in the municipality of Holtålen in Sør-Trøndelag county, Norway. It is located approximately south of the city of Trondheim, approximately north of Røros mining town, and about southwest of Ålen/Renbygda. About 150 people live in the valley.In the...

 valley in the municipality of Holtålen
Holtålen
Holtålen is a municipality in Sør-Trøndelag county, Norway. It is part of the Gauldalen region. The administrative centre of the municipality is the village of Ålen. Other villages include Hessdalen, Aunegrenda, Haltdalen, and Renbygda.-General information:...

 in Sør-Trøndelag
Sør-Trøndelag
- References :...

 county, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

.

History and description

Unusual lights have been reported here since 1940s or earlier. Especially high activity of Hessdalen lights took place from December 1981 until the summer of 1984 when lights were observed 15 to 20 times per week. The frequency of the lights caused a gathering of numerous tourists staying there overnight to see the phenomenon. Since then, the activity has decreased and now the lights are observed some 10 - 20 times per year.

The Hessdalen light most often is a bright, white or yellow light of unknown origin standing or floating above the ground level. Sometimes the light can be seen for more than one hour. There are several other types of unexplained lights observed in the Hessdalen valley.

Research

Since 1983 there has been ongoing scientific research often nicknamed "Project Hessdalen", initiated by Dr. Erling Strand. In 1998, the Hessdalen AMS
Hessdalen AMS
The Hessdalen Automatic Measurement Station is an automatically working observation station in the Hessdalen area in the municipality of Holtålen in Sør-Trøndelag county, Norway. It is used for registering Hessdalen lights...

 automated scientific research station was built in the valley. It registers and records the appearance of lights.

Later, the EMBLA program was initiated. It brings together established scientists and students into researching these lights. Leading research institutions are Østfold University College
Østfold University College
Østfold University College is a further and higher education institution in south-eastern Norway. It has campuses in Fredrikstad and Halden. Enrollment is approximately 4,000 students ; and 480 staff...

 (Norway) and the Italian National Research Council
Consiglio Nazionale delle Ricerche
The Consiglio Nazionale delle Ricerche or National Research Council, is an Italian public organization set up to support scientific and technological research. Its headquarters are in Rome.-History:The institution was founded in 1923...

.

Possible explanations

In spite of on-going research there is no convincing explanation to the origin of these lights. However, there are numerous working hypotheses.
  • One explanation attributes the phenomenon to an incompletely understood combustion
    Combustion
    Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

     process in the air involving clouds of dust from the valley floor containing scandium
    Scandium
    Scandium is a chemical element with symbol Sc and atomic number 21. A silvery-white metallic transition metal, it has historically been sometimes classified as a rare earth element, together with yttrium and the lanthanoids...

    . Some sightings though, have been identified as misperceptions of astronomical bodies, aircraft, car headlights, and mirage
    Mirage
    A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. The word comes to English via the French mirage, from the Latin mirare, meaning "to look at, to wonder at"...

    s.

  • One recent hypothesis
    Hypothesis
    A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

     suggests that the lights are formed by a cluster of macroscopic Coulomb crystals in a plasma
    Plasma (physics)
    In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...

     produced by the ionization
    Ionization
    Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...

     of air and dust by Alpha particle
    Alpha particle
    Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...

    s during radon
    Radon
    Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...

     decay in the dusty atmosphere. Several physical properties (oscillation
    Oscillation
    Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...

    , geometric structure, and light spectrum) observed in Hessdalen lights phenomenon can be explained through the dust plasma model. Radon decay produces alpha particles (responsible by helium emissions in HL spectrum) and radioactive elements such as polonium
    Polonium
    Polonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie Skłodowska-Curie and Pierre Curie. A rare and highly radioactive element, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Polonium has been studied for...

    . In 2004, Teodorani showed an occurrence where a higher level of radioactivity on rocks was detected near the area where a large light ball was reported. In fact, when radon is released into air, its solid decay products readily attach to airborne dust. A new computer simulation shows that dust immersed in ionized gas (i.e., dusty plasma
    Dusty plasma
    A dusty plasma is a plasma containing nanometer or micrometer-sized particles suspended in it. Dust particles may be charged and the plasma and particles behave as a plasma, following electromagnetic laws for particles up to about 10 nm...

    s) can organize itself into double helixes. The simulations suggested that under conditions commonly found in space, the dust particles first form a cylindrical structure that sometimes evolved into helical structures. Along some spirals, the radius of the helix was seen to change abruptly from one value to another and then back again, providing a mechanism for storing information in terms of the length and radius of a section of a spiral. Hessdalen Lights may take the helical structure. Surprisingly, dusty plasmas may also assume this structure.
  • Another hypothesis
    Hypothesis
    A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

     explains HL as a product of piezoelectricity
    Piezoelectricity
    Piezoelectricity is the charge which accumulates in certain solid materials in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure...

     generated under specific rock strains (Takaki and Ikeya, 1998) because many crystal rocks include quartz
    Quartz
    Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

     grains which produce an intense charge density
    Charge density
    The linear, surface, or volume charge density is the amount of electric charge in a line, surface, or volume, respectively. It is measured in coulombs per meter , square meter , or cubic meter , respectively, and represented by the lowercase Greek letter Rho . Since there are positive as well as...

    . In recent paper, based in the dusty plasma theory of HL (Paiva and Taft, 2010), it is suggested that piezoelectricity of quartz cannot explain a peculiar property assumed by the HL phenomenon – the presence of geometrical structures in its center.

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