"A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.
Rainbows can be full circles; however, the average observer sees only an arc formed by illuminated droplets above the ground, and centred on a line from the sun to the observer's eye.
In a primary rainbow, the arc shows red on the outer part and violet on the inner side. This rainbow is caused by light being refracted when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it.
In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colours reversed, with red on the inner side of the arc."
"A rainbow is not located at a specific distance from the observer, but comes from an optical illusion caused by any water droplets viewed from a certain angle relative to a light source. Thus, a rainbow is not an object and cannot be physically approached. Indeed, it is impossible for an observer to see a rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the light source. Even if an observer sees another observer who seems "under" or "at the end of" a rainbow, the second observer will see a different rainbow—farther off—at the same angle as seen by the first observer.
Rainbows span a continuous spectrum of colours. Any distinct bands perceived are an artefact of human colour vision, and no banding of any type is seen in a black-and-white photo of a rainbow, only a smooth gradation of intensity to a maximum, then fading towards the other side. For colours seen by the human eye, the most commonly cited and remembered sequence is Newton's sevenfold red, orange, yellow, green, blue, indigo and violet, remembered by the mnemonic, Richard Of York Gave Battle In Vain (ROYGBIV).
Rainbows can be caused by many forms of airborne water. These include not only rain, but also mist, spray, and airborne dew."
An Optical Effect: An Impossible Place To Reach
"Rainbows occur frequently in mythology, and have been used in the arts. One of the earliest literary occurrences of a rainbow is in Genesis 9, as part of the flood story of Noah, where it is a sign of God's covenant to never destroy all life on earth with a global flood again. In Norse mythology, the rainbow bridge Bifröst connects the world of men (Midgard) and the realm of the gods (Asgard). Cuchavira was the god of the rainbow for the Muisca people in present-day Colombia and when the regular rains on the Bogotá savanna were over, the people thanked him offering gold, snails and small emeralds. The Irish leprechaun's secret hiding place for his pot of gold is usually said to be at the end of the rainbow. This place is appropriately impossible to reach, because the rainbow is an optical effect which cannot be approached.
Rainbows sometimes appear in heraldry too, even if its characteristic of multiple colours doesn't really fit in to the usual heraldic style.
Rainbow flags have been used for centuries. It was a symbol of the Cooperative movement in the German Peasants' War in the 16th century, of peace in Italy, and of gay pride and LGBT social movements since the 1970s. In 1994, Archbishop Desmond Tutu and President Nelson Mandela described newly democratic post-apartheid South Africa as the rainbow nation. The rainbow has even been used in technology product logos including the Apple computer logo. Many political alliances have called themselves Rainbow coalition."
"Rainbows occur frequently in mythology, and have been used in the arts. One of the earliest literary occurrences of a rainbow is in Genesis 9, as part of the flood story of Noah, where it is a sign of God's covenant to never destroy all life on earth with a global flood again. In Norse mythology, the rainbow bridge Bifröst connects the world of men (Midgard) and the realm of the gods (Asgard). The Irish leprechaun's secret hiding place for his pot of gold is usually said to be at the end of the rainbow. This place is appropriately impossible to reach, because the rainbow is an optical effect which cannot be approached."
The Rainbow Represents Art
The Rainbow Represents the Tones or Notes of the Musical Scale
"The rainbow has a place in legend owing to its beauty and the historical difficulty in explaining the phenomenon.
In Hindu religion, the rainbow is called Indradhanush, meaning "the bow (Sanskrit and Hindi: dhanush is bow) of Indra, the god of lightning, thunder and rain". Another Indian mythology says the rainbow is the bow of Rama, the incarnation of Vishnu. It is called Rangdhonu in Bengali, dhonu (dhanush) meaning bow. Likewise, in mythology of Arabian Peninsula, the rainbow, called Qaus Quzaħ in Arabic, is the war bow of the god Quzaħ.
In Armenian mythology the rainbow is a belt of Tir, a Sun god.
The Irish leprechaun's secret hiding place for his pot of gold is usually said to be at the end of the rainbow. This place is impossible to reach, because the rainbow is an optical effect which depends on the location of the viewer. When walking towards the end of a rainbow, it will appear to "move" further away (two people who simultaneously observe a rainbow at different locations will disagree about where a rainbow is). Also, a rainbow is in fact a full circle, we usually only see the half arc of it due to our positioning in respect to it; if you were to be positioned higher up (such as on a tall building or an airplane) then you could view it's actual full circle. So in reality there is no end to a rainbow, just as there is no end to a circle. Therefore, that 'end of the rainbow' is in other words an impossible/non-existent place.
Another ancient portrayal of the rainbow is given in the Epic of Gilgamesh: the rainbow is the "jewelled necklace of the Great Mother Ishtar" that she lifts into the sky as a promise that she "will never forget these days of the great flood" that destroyed her children. (The Epic of Gilgamesh, Tablet Eleven)
Then Ishtar arrived. She lifted up the necklace of great jewels that her father, Anu, had created to please her and said, "Heavenly gods, as surely as this jewelled necklace hangs upon my neck, I will never forget these days of the great flood. Let all of the gods except Enlil come to the offering. Enlil may not come, for without reason he brought forth the flood that destroyed my people."
According to Genesis, after Noah's flood God put the rainbow in the sky as the sign of His promise that He would never again destroy the earth with flood (Genesis 9:13–17):
I do set my bow in the cloud, and it shall be for a token of a covenant between me and the earth. And it shall come to pass, when I bring a cloud over the earth, that the bow shall be seen in the cloud: And I will remember my covenant, which is between me and you and every living creature of all flesh; and the waters shall no more become a flood to destroy all flesh. And the bow shall be in the cloud; and I will look upon it, that I may remember the everlasting covenant between God and every living creature of all flesh that is upon the earth. And God said unto Noah, This is the token of the covenant, which I have established between me and all flesh that is upon the earth.
The Church of Jesus Christ of Latter-Day Saints founder and prophet Joseph Smith stated that the second coming of the Christ would not occur in any year in which a rainbow is seen.
In Amazonian cultures, rainbows have long been associated with malign spirits that cause harm, such as miscarriages and (especially) skin problems. In the Amuesha language of central Peru, certain diseases are called ayona’achartan, meaning "the rainbow hurt my skin". A tradition of closing one's mouth at the sight of a rainbow in order to avoid disease appears to pre-date the Incan empire.
"Rainbows are generally described as very colourful and peaceful. The rainbow occurs often in paintings. Frequently these have a symbolic or programmatic significance (for example, Albrecht Dürer's Melancholia I). In particular, the rainbow appears regularly in religious art (for example, Joseph Anton Koch's Noah's Thank Offering). Romantic landscape painters such as Turner and Constable were more concerned with recording fleeting effects of light (for example, Constable's Salisbury Cathedral from the Meadows). Other notable examples appear in work by Hans Memling, Caspar David Friedrich, and Peter Paul Rubens."