Little Bits of History


Posted in History by patriciahysell on April 20, 2015
Vädersolstavlan, sun dogs over Stockholm

Vädersolstavlan, sun dogs over Stockholm

April 20, 1535: Sun dogs appear in Stockholm. For two hours in the morning on this date, the skies over Stockholm were filled with white circles and arcs spreading across the sky. Additional suns (sun dogs) appeared around the morning sun. Many unknown phenomena were attributed to an angry God and this was no exception. God was said to be upset with King Gustav Vasa for introducing Protestantism into Sweden as well as his hard treatment of allies to his enemy, the Danish king. The Lutheran scholar Olaus Petri hoped to forestall rumors and ordered a painting produced to document the event. Vädersolstavlan (artist unknown but attributed to Urban Målare), did not help since the king saw it as a conspiracy.

Sun dogs are also called mock suns or phantom suns. Their scientific name is parhelia with parhelion being the singular. They are an atmospheric phenomenon where two bright spots appear around the sun, one on each side. There is often a luminous ring known as a 22⁰ halo at the same time. Sun dogs are a subset of halos which also include light pillars. Ice crystals suspended in cirrus or cirrostratus clouds about 3-6 miles up in the sky (the upper troposphere) are responsible. In cold weather, ice crystals lower to the ground can also produce the phenomenon. When this happens, they are called diamond dust.

The ice crystals act as prisms or mirrors and reflect or refract the light. They may split up into colors because of dispersion. The halo effect appears as a large ring round the Sun or Moon and has a radius of about 22⁰, hence the name. These ice crystals are semi-random in the atmosphere. Because of the arrangement of the crystals, no light is reflected back inside the circle and it makes the sky appear darker inside the halo and gives an impression of a “hole in the sky”. This is not a corona, an entirely different phenomenon. For sun dogs and light pillars, the ice crystals need to be in a horizontal alignment.

Sun dogs can be seen anywhere in the world during any season. They are most obvious and brightest when they are close to the horizon. Usually, the ice crystals involved are plate-shaped and hexagonal. The weather is usually very cold. The crystals act as prisms and light passes through them at a minimum deflection of 22⁰. As the crystals float down in the atmosphere, their large faces are almost horizontal to the sunlight. This makes the sun dogs appear to the right and left of the Sun. Since larger plates wobble more as they drift, they produce taller sun dogs. They are red colored at the edge closer to the sun and the colors fade through oranges to blue at the other side. The colors overlap and are not as distinct as in a rainbow. The reason for the term “sun dog” is unknown but seems to be Scandinavian in origin.

You’ve seen the sun flatten and take strange shapes just before it sinks in the ocean. Do you have to tell yourself every time that it’s an illusion caused by atmospheric dust and light distorted by the sea, or do you simply enjoy the beauty of it? – John Steinbeck

It is better to have your head in the clouds, and know where you are… than to breathe the clearer atmosphere below them, and think that you are in paradise. – Henry David Thoreau

Get your head out of the clouds. Stop huffing the atmosphere. – Jarod Kintz

There are no walls in the atmosphere. – Kim Prather

Also on this day: Whodunit? – In 1841, the first mystery story is published.
Germ Theory – In 1862, Pasteur demonstrated his new theory.
Ludlow Massacre – In 1914, mining riots took place in Colorado resulting in 22 dead.
Two – In 1964, BBC2 launched.
Annie Hall – In 1977, the movie premiered.

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