Rainbow

A rainbow is an optical and meteorological phenomenon that causes a nearly continuous spectrum of light to appear in the sky when the sun shines onto falling rain. It is a multicoloured arc with red on the outside and violet on the inside. The full sequence of colours is most commonly cited as red, orange, yellow, green, blue, indigo, and violet, though it is important to note that this is an inconsistent list; all primary and secondary colors are present in some form, but only one tertiary. It is commonly thought that indigo was included due to the different religious connotations of the numbers six and seven at the time of Isaac Newton's work on light, despite its lack of scientific significance and the poor ability of humans to distinguish colors in the blue portion of the visual spectrum.

Rainbows in religion and mythology

The rainbow has a place in legend due to its beauty and the difficulty in explaining the phenomenon before Galileo's treatise on the properties of light.

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• In Greek mythology, it is a path made by a messenger (Iris) between Earth and Heaven.
• In the Hebrew Bible, the rainbow is a symbol of the covenant between God and man, and God's promise to Noah that He would never again flood the Earth.
• The Irish leprechaun's secret hiding place for his crock of gold is usually said to be at the end of the rainbow.
• In Chinese mythology, the rainbow was a slit in the sky sealed by Goddess Nüwa using stones of seven different colours.
• In Hindu mythology, the rainbow is called Indradhanush—meaning the bow of Indra, the God of lightning and thunder.
• In Norse Mythology, a rainbow called the Bifrost Bridge connects the realms of Ásgard and Midgard, homes of the gods and humans, respectively.