60 Fun Facts About Rainbow

A rainbow caused by sunlight always appears in which part of the sky?

The centre of the arc lies on a line running from the Sun through the back of your head.

In a primary rainbow, which colour is on the outer edge of the arc?

Red light leaves the raindrop at the widest angle, so it forms the outside of the bow.

At roughly what angle from the antisolar point does the primary rainbow appear?

Light returned from a raindrop piles up at that turning-point angle, and it does not depend on the size of the drop.

Which three things happen to sunlight inside a raindrop to make a rainbow?

The light bends on entry, bounces off the back of the drop and bends again on the way out, splitting into colours.

Why are rainbows usually seen in the western sky in the morning?

By early evening the geometry flips and the bow shows up in the east.

From where can a rainbow sometimes be seen as a complete circle?

Every rainbow is really a circle; the ground simply hides its lower half from most observers.

Roughly how far outside the primary bow does the secondary rainbow of a double rainbow appear?

It is caused by two reflections inside each drop, and its colours run in the reverse order.

What is the name for the strip of darker sky between a primary and a secondary rainbow?

It honours Alexander of Aphrodisias, the Greek commentator who first described it around AD 200.

Why is a secondary rainbow always fainter than the primary?

In theory every rainbow is a double rainbow; the second bow is just often too weak to spot.

Isaac Newton originally split the spectrum into how many main colours before adding orange and indigo?

He went up to seven partly to match the number of notes in a musical scale.

Newton settled on seven rainbow colours by analogy with what?

Scholars note that what he called 'blue' we would now call cyan, and his 'indigo' is closer to today's blue.

'Richard Of York Gave Battle In Vain' is a mnemonic for what?

It is said to recall Richard, Duke of York's death at the Battle of Wakefield in 1460, and shares its initials with 'Roy G. Biv'.

A rainbow made by moonlight rather than sunlight is called what?

They are so dim that most people see them as white, because our colour vision is poor in low light.

Which waterfall on the Zambia–Zimbabwe border is famous for its spray moonbows?

In the US, Cumberland Falls in Kentucky and Yosemite are also known for them.

Why does a fog bow look almost white instead of coloured?

Fog droplets are under 0.05 mm across; sailors sometimes call the result a sea-dog.

Sun dogs, the bright spots that flank the Sun, are caused by light passing through what?

The plate-shaped crystals act as prisms and bend light by a minimum of 22°, which is why the spots sit 22° either side of the Sun.

The circumhorizontal arc, or 'fire rainbow', appears only when the Sun is at least how high above the horizon?

That makes it a rarity at high latitudes; it is a halo formed in ice crystals, not a true rainbow at all.

A rainbow on Saturn's moon Titan would have a radius of about 49° instead of 42°. Why?

Titan's hazy skies would make visible rainbows rare, but infrared ones might be common.

In what year was a third-order (tertiary) rainbow first definitively photographed in nature?

Third- and fourth-order bows form on the Sun's side of the sky, so they are usually lost in the glare.

Which classical Greek scholar was the first to devote serious attention to explaining the rainbow?

His qualitative account was flawed but went unmatched for centuries; much later rainbow theory was a reaction to it.

Which medieval English friar first calculated the angular size of the rainbow, in his Opus Majus of 1268?

He stated the summit of a rainbow can never appear more than 42° above the horizon.

Which Song-dynasty Chinese polymath proposed that rainbows form when sunlight meets raindrops in the air?

His explanation, based on atmospheric refraction, is described as basically in line with modern science.

Whose 1637 Discourse on Method explained the rainbow with experiments on a water-filled glass sphere?

He also studied the effect using a Florence flask, having noticed drop size did not change the bow.

In Greek mythology, which goddess personifies the rainbow and serves as messenger to the Olympians?

She was usually shown as a winged young woman with a herald's staff and a pitcher of water for the gods.

In Norse mythology, the burning rainbow bridge Bifrost connects Midgard to which realm?

A god stands guard at its far end, and its red is said to be fire that keeps the frost giants from strolling into heaven.

Which Norse god lives at Himinbjörg and guards Bifrost from the giants?

The bridge is fated to break under the forces of Muspell during Ragnarök.

The Rainbow Serpent, a creator deity linked to water, comes from the mythology of which people?

A reliable waterhole is often regarded as the serpent's permanent home, and a rainbow is the serpent moving between them.

In the Book of Genesis, the rainbow is set as a token of God's promise after which event?

An even older literary rainbow appears after a flood in the Epic of Gilgamesh.

Cuchavira, a rainbow god thanked with gold, snails and emeralds when the rains ended, belonged to which people?

The offerings were made when the regular rains on the Bogotá savanna were over.

Which two-headed creature represents the rainbow in Chinese mythology?

Rainbow deities elsewhere include Manzat in Mesopotamia and Anuenue, the rainbow maiden of Hawaiian legend.

In Irish folklore, which creature is said to keep a pot of gold at the end of the rainbow?

Before the 20th century he was generally said to wear red, not green, and his main trade was cobbling shoes.

Which artist created the rainbow pride flag, first flown in San Francisco in June 1978?

He refused to trademark it, seeing the flag as belonging to the whole community.

How many stripes did the original 1978 rainbow pride flag have?

One stripe went first because its fabric was hard to source, then turquoise, leaving the familiar six.

Which colour was dropped from the pride flag first because its fabric was not readily available?

Demand for the flag surged after Harvey Milk's assassination in November 1978, and supply had to keep up.

Which archbishop coined the term 'rainbow nation' for post-apartheid South Africa?

It followed the country's first democratic election in 1994 and was taken up by Nelson Mandela.

Which country's intelligence service bombed Greenpeace's Rainbow Warrior in Auckland in 1985?

The ship was preparing to lead a protest flotilla against nuclear tests at Mururoa Atoll; photographer Fernando Pereira was killed.

Rainbow Row, a run of thirteen pastel-painted historic houses, is a landmark of which US city?

The first were painted pink in 1931 on a colonial Caribbean colour scheme, and the neighbours followed.

Rainbow Bridge National Monument, one of the world's largest natural arches, is in which US state?

The Navajo name Nonnezoshe means 'rainbow turned to stone', and Teddy Roosevelt and Zane Grey were among the first tourists to trek in.

The Rainbow Bridge at Niagara Falls replaced an earlier bridge that collapsed in 1938. What destroyed it?

The new steel arch opened in November 1941 and got its name because rainbows form so often in the falls' spray.

Tokyo's Rainbow Bridge links Shibaura Pier with which waterfront district?

Its cable lamps glow red, white and green each night on solar power stored during the day.

In which country did a teenager write the 'Rainbow Bridge' pet-afterlife story in 1959?

Edna Clyne-Rekhy wrote it to mourn her dog Major; copies circulated for decades without her name.

'Over the Rainbow' was nearly cut from The Wizard of Oz. What did the studio worry about?

The producer and director insisted it stay; it went on to win the Academy Award for Best Original Song.

Who composed the music for 'Over the Rainbow'?

Yip Harburg wrote the words; the RIAA later ranked it number one on its Songs of the Century list.

The hard rock band Rainbow was formed in 1975 by which guitarist after he left Deep Purple?

Its first singer was Ronnie James Dio, poached from the American band Elf.

Who hosted the PBS children's series Reading Rainbow from 1983 to 2006?

It picked up 26 Emmys and a Peabody, and his sign-off line was 'But you don't have to take my word for it'.

Zippy, George and Bungle starred in Rainbow, a long-running children's show on which country's TV?

Made by Thames Television from 1972 to 1992, it was originally conceived as a British answer to Sesame Street.

Rainbow Brite, the 1984 cartoon and doll franchise, was created by which company?

Hallmark licensed the dolls to Mattel and backed the launch with a $15 million ad campaign.

Rainbow Road is a notoriously difficult track that usually closes out which video game series?

Most versions are set in space with few or no guardrails, so falling off is the main hazard.

Which candy's advertising slogan is 'Taste the Rainbow'?

The theme was created by New York agency D'Arcy Masius Benton & Bowles; the trademark dates to 1974.

The steelhead, the sea-run form of the rainbow trout, is the official state fish of which US state?

Rainbow trout have been introduced to at least 45 countries and now sit on the list of the world's 100 worst invasive species.

Vinicunca, Peru's 'Rainbow Mountain', gets its coloured stripes from what?

It sits at over 5,000 metres near Cusco and only became a mass tourist draw after its glacier cap melted away in 2013.

The rainbow eucalyptus, famous for its multicoloured peeling bark, is native to which region?

It is the only eucalyptus that normally grows in rainforest, with a range reaching into the Northern Hemisphere.

In which city did Fred Hampton's Black Panthers form the original 1969 Rainbow Coalition with the Young Lords?

It united Black, Puerto Rican and poor white activists years before Jesse Jackson revived the name nationally.

What are the faint pastel bands sometimes seen just inside the violet edge of a primary rainbow called?

They come from interference between rays taking slightly different paths through the drops, something classical geometric optics cannot explain.

What causes the very rare twinned rainbow, in which two arcs split from a single base?

Larger drops flatten more as they fall; a mix of 0.40 and 0.45 mm droplets was enough to explain one photographed example.

Up to how many separate bows can be seen when reflected and reflection rainbows occur at once?

The normal primary and secondary appear with their reflections below the horizon, plus the reflection bows and their own reflections.

Why does a shower at sunrise or sunset sometimes produce a rare all-red rainbow?

With blue and green stripped out of the low sunlight, the result is a dramatic monochrome bow.

Which Roman philosopher's Naturales Quaestiones, around AD 65, noted rainbows in spray from oars and burst pipes?

He even described colours produced by little glass rods, anticipating Newton's prism experiments.

Which Persian scholar, a student of Qutb al-Din al-Shirazi, gave a mathematically satisfying rainbow model around 1300?

He proposed sunlight refracted twice in a drop with reflections in between, and tested it with a water-filled glass sphere.

Modern physical descriptions of the rainbow rest on scattering theory published in 1908 by whom?

George Biddell Airy had earlier explained how droplet size governs the strength of the colours.