Shiranui (Optical phenomenon)

This article is about the Japanese atmospheric optical phenomenon. For other uses, see Shiranui (disambiguation).

Shiranui from the Shokoku Rijindan by Kikuoka Tenryō

Shiranui from the Konjaku Gazu Zoku Hyakki by Toriyama Sekien

Shiranui (不知火, unknown fire, Shiranuhi in the historical kana orthography) is an optical phenomenon characterized by moving, changing fires which appear on the horizon of the Ariake Sea and the Yatsushiro Sea, Kumamoto Prefecture, Japan on the night of special days (August 1 of Chinese calendar). It had been long believed to be a mysterious, fiery yōkai, but today, scientific explanation has been made and it may appear on other days,too. It is a mixture of mirage.

Terminology

Shiranui is not will-o'-the-wisp.

Origin of the word Shiranui

Mythology: In the days of mythology, Emperor Keiko (景行天皇, Keiko-tenno), the 12th emperor of Japan according to the traditional order of succession, in his journey for expanding the Yamato Ouken, saw unexplainable spots of moving fire, Shiranui, in the Ariake Sea and the Yatsushiro Sea (also called the Shiranui Sea), and a gozoku in that land replied that he did not know the fire, the origin of Shiranui.

• For Yamato Ouken, see History of Kumamoto Prefecture#Explanation of Yamato Ouken
• Hence, this light was named Shiranui (the light I don't know) and the area was named Hi Province (火国 or 肥国, Hi no kuni , land or country of fire), now Kumamoto Prefecture.

Shiranui written in 1835

In 1835, Nakashima Hiroashi wrote a book entitled "On the Shiranui".

Many people gather to witness Shiranui even from remote areas. I myself watched Shiranui many times. The Shiranui appears 8 to 12 kilometers distant from the seashore, but it was not sure since it was very dark. At first, one or two spots of fire appear late at night. This is named oya-dama or father fire. Then, the distance between the fires becomes longer, and subsequently, spots of fires appear and disappear as time goes by, and late at night it may become continuous. The lights appear like stars. At dawn, they disappear. When rain and strong wind come, Shiranui does not appear. Many people watch Shiranui from mountains, and they enjoy drinking sake there.

Investigations of Shiranui with more than 50 people

In the Taisho era, Shiranui attracted the attention of many people, including scholars and newspapermen. There was a large scale investigation with two ships and more than 50 people in the Ariake sea in 1916. However, they reported conflicting data and no scientific clarification was reached.

Shiranui written in English in 1916

• The Unknown Fire
• From time immemorial, the Gulf of Shimabara, (near Ariake sea), Japan, has been famed for SHIRANUI, the unknown fire, which appears from time to time. The phenomenon occurs twice a year, about 30th September and 24th February, from some time after midnight until the approach of dawn. Sometime the light is a large ball of fire rising from the surface of the sea to a height of 60 feet; sometimes it is a line of pale red, firery globes drifting and down the tide.

Hypotheses of Shiranui

1. Dragon which lives under the sea emitting light.
2. Reflection of star lights
3. Luminous jellyfish
4. Fire from undersea active volcano
5. Flying saucers
6. Fireballs(ghosts)
7. Light of fishing boats

Studies on Shiranui by Modern Scientists

Machika Miyanishi , Professor of Kumamoto Higher Technical School and Hiroshima Higher Technical School, made extensive scientific studies and wrote 8 papers including two English papers. His conclusion was: the light source of Shiranui was that of fishing boats. Large tideland forms lumps of air of different temperatures on special days, and by the voltex movement of air lumps, the light appears as deformed fluctuation in images of light. Tairi Yamashita , Professor at Kumamoto University, made extensive studies of Shiranui using modern instruments with the assistance of students. He concluded that there is a very complex distribution of heated air lumps and cold air lumps which constantly change. Light from distant sources repeatedly fluctuates, and either increases or decreases or disappears. In some cases, light is split. These changes appear to the observer changing greatly and irregularly. Under the same conditions, Shiranui may appear in other seasons.

References

• A study of Shiranui. Miyanishi Machika. Dainippon Shuppan Kabushiki Kaisha. 1943.
• A collection of references on Shiranui. Shiranui reference collecting committee. 1993. Shiranui Town.
• Investigation on Shiranui I. Tairi Yamashita. Kumamoto University Department of Education Kiyo. Vo. 21 1972.
• Investigation on Shiranui II Tairi Yamashita. Kumamoto University Department of Education Kiyo. Vol. 33, 1984.
• Changes of Shiranui in Photographs with the passage of time. Nobuyuki Marume. in the Collection.
• A study of Shiranui. Tairi Yamashita. 1994. Ashi Shobou. ISBN 4-7512-0576-5
• A new study of Shiranui. Iwao Tateishi.1994. Tsukiji Shokan. ISBN 4-8067-1047-4