Everything You Need to Know About Rainbows: Nature’s Most Breathtaking Light Show

There are few things in nature that stop people in their tracks quite like a rainbow. One moment you’re going about your day, and then suddenly the sky erupts in a perfect arc of color — red, orange, yellow, green, blue, indigo, violet — hanging in the air as if painted there by some invisible hand. For most of us, the instinct is immediate: point, gasp, grab your phone. But beyond that first rush of wonder, how much do you actually know about what you’re looking at?

Rainbows are one of those phenomena that sit right at the intersection of science and beauty. Understanding how they work doesn’t diminish the magic at all — if anything, knowing the physics behind them makes the next one you see even more astonishing. This guide covers everything: the science, the types, the myths, the best ways to see them, and why they continue to captivate human beings across every culture and century.

What Exactly Is a Rainbow?

A rainbow is an optical phenomenon caused by the interaction of sunlight and water droplets in the atmosphere. When sunlight enters a water droplet, it slows down and bends — a process called refraction. The light then reflects off the inside back wall of the droplet and exits, bending again as it leaves. Because different wavelengths of light (which we perceive as different colors) bend at slightly different angles, they spread apart as they exit the droplet. This separation of white light into its component colors is called dispersion.

What you see in the sky is the result of millions of these tiny interactions happening simultaneously, with each droplet sending a single color of light toward your eye depending on the angle between you, the droplet, and the sun. The result is a curved band of color that always appears as an arc — and always in the same order, with red on the outside and violet on the inside.

The angle of refraction is remarkably consistent. Red light exits water droplets at about 42 degrees relative to the incoming sunlight, while violet exits at about 40 degrees. That two-degree difference is what separates the colors across the arc. It also explains why a rainbow always appears opposite the sun — you must have the sun behind you and rain (or mist) in front of you to see one.

Why Is a Rainbow Always an Arc?

This is one of the most common questions people have, and the answer is elegant. The specific angle at which light exits a raindrop and reaches your eye is fixed by the physics of refraction and reflection. All the droplets that are positioned at exactly 42 degrees from your line of sight relative to the sun will send red light to your eye at the same moment. Because that angle is constant in every direction around the line between you and the sun, the set of all those droplets forms a circle — or more precisely, a cone with your eye at the tip.

When you’re standing on the ground, the earth cuts that circle off, so you only see the top portion: an arc. If you were floating in the air — say, in an airplane or a helicopter, under the right conditions — you could theoretically see a complete circular rainbow. This has been photographed, and it’s exactly as spectacular as it sounds.

The center of any rainbow, if you extended the arc into a full circle, would always fall at a point directly opposite the sun from your perspective — called the antisolar point. That point is always located at your shadow’s head, which is why you can never reach the end of a rainbow. As you move, the antisolar point moves with you, and the rainbow shifts accordingly.

The Colors of the Rainbow: ROYGBIV

The traditional list of rainbow colors — red, orange, yellow, green, blue, indigo, and violet — is often remembered through the mnemonic ROY G BIV, or the imaginary name “Roy G. Biv.” This ordering was largely codified by Isaac Newton, who first described the spectrum in the 17th century after famously passing sunlight through a glass prism and studying the results.

Newton actually chose to include seven colors, partly because he wanted the rainbow’s color count to match the seven notes of the musical scale, which reflects the era’s belief in mathematical harmony across natural phenomena. Modern physicists tend to acknowledge that the division into seven is somewhat arbitrary — the spectrum is a continuous gradient with no hard lines between the colors. Orange doesn’t suddenly begin where red ends. But the seven-color framework remains enormously useful for communication and education, and it maps closely enough to how most people perceive the transitions.

Interestingly, color perception is also subjective. Cultures around the world historically divided the rainbow into different numbers of colors — some languages don’t distinguish between blue and green at all, while others have far more granular color vocabulary than English. A Japanese child and an English-speaking child looking at the same rainbow may genuinely perceive a different number of color bands, not because their eyes work differently, but because their visual systems have been trained by language and culture to draw different categorical lines.

Double Rainbows: What Are They and Why Do They Happen?

If you’ve spent enough time watching the sky, you’ve probably seen a double rainbow — a second, fainter arc appearing above the first. Double rainbows became a cultural phenomenon after a widely shared video from 2010 in which a man expressed overwhelmed, joyful astonishment at seeing one. His reaction, though widely mocked and celebrated at the same time, was actually not inappropriate. Double rainbows are genuinely spectacular.

A double rainbow occurs when light reflects twice inside the water droplet before exiting, rather than just once. This second reflection reverses the order of colors, so in a double rainbow, the outer arc has violet on the outside and red on the inside — the reverse of the primary rainbow. The secondary rainbow also appears at a wider angle (around 51 degrees) and is always noticeably dimmer than the primary, because some light is lost with each reflection.

Between the two bows, there is often a noticeably darker band of sky called Alexander’s dark band, named after Alexander of Aphrodisias, who described it in the third century. The darkness occurs because raindrops in that region of the sky send light to eyes at angles outside both bows, meaning that region receives less scattered light than the areas inside or outside the arcs.

Rare and Unusual Rainbow Types

The standard arc rainbow is just the beginning. There are a surprising number of rainbow variants, each produced by slightly different atmospheric or lighting conditions.

Fogbows are perhaps the most striking of the variants. These form exactly like rainbows but occur in fog rather than rain. Because fog droplets are so much smaller than raindrops, the diffraction of light dominates and the colors wash out almost entirely, leaving a pale white or very faintly tinted arc. They’re also called ghost rainbows or white rainbows, and spotting one on a misty morning near the ocean or in the mountains is an eerie and beautiful experience.

Moonbows, or lunar rainbows, are rainbows produced by moonlight rather than sunlight. Because moonlight is so much dimmer, moonbows are usually too faint for the human eye to register in color — our color vision requires a certain threshold of light to function — so they tend to appear white or silver to the naked eye. Long-exposure photographs, however, can capture their full spectral color. They’re most often seen near large waterfalls with persistent mist on nights around the full moon.

Supernumerary rainbows are the delicate, pastel, closely spaced bands sometimes visible just inside the main arc of a rainbow. They’re caused by interference effects between light waves — a phenomenon that belongs to the wave nature of light rather than the geometric optics that explain the main arc. Supernumerary bands are more visible when raindrops are particularly uniform in size, making them a somewhat rare treat.

Reflected rainbows and reflection rainbows are two distinct phenomena that both involve nearby bodies of water. A reflected rainbow appears when sunlight first reflects off a calm water surface before entering the raindrops, producing an arc that intersects with the primary rainbow. A reflection rainbow is simply the mirror image of the primary rainbow reflected in the water below — it curves downward into the surface rather than upward into the sky.

The Science of Why You Can Never Reach a Rainbow

The rainbow you see is entirely personal to your position. Someone standing ten feet to your left is seeing a slightly different rainbow — formed by different water droplets at the right angle for their particular eye position. There is no “location” in the sky where the rainbow exists. It’s not a physical object at all, but a perception — a relationship between your eye, the light, and the droplets that exist around you.

This means that as you move toward a rainbow, it moves with you. Its apparent position in the sky remains constant relative to your perspective, always at that same antisolar angle. You will never get closer to it, and you will never find the end of it on the ground — which is, of course, the legendary home of the leprechaun’s pot of gold in Irish folklore. The impossibility is built into the physics from the start.

Rainbows Across Human Culture and Mythology

Long before anyone understood the optics, people were trying to make sense of rainbows. Nearly every major culture on earth has a rainbow tradition, and many of them share certain themes: the rainbow as bridge, as messenger, as serpent, or as boundary between the mortal world and the divine.

In Norse mythology, the Bifrost is a burning rainbow bridge connecting Midgard (the human world) to Asgard (the realm of the gods). Only the gods and the heroic dead could travel it. The imagery is remarkably consistent with the idea of the rainbow as a threshold — a boundary between ordinary experience and something transcendent.

In ancient Greek mythology, Iris was the goddess of the rainbow and a messenger of the gods, particularly of Hera and Zeus. She traveled between the divine and human realms along the rainbow’s arc, delivering messages and instructions.

Indigenous cultures across Mesoamerica, Africa, and Oceania frequently associated rainbows with serpents — often enormous, sky-spanning creatures that drank from rivers and lakes. The Rainbow Serpent of Aboriginal Australian traditions is one of the oldest and most enduring creator figures in any known mythology, associated with fertility, water, and the formation of the landscape itself.

In the Hebrew Bible, the rainbow appears as a sign of God’s covenant with Noah after the flood — a promise that the earth will never again be destroyed by water. This tradition carries into Christianity and Islam as well, giving the rainbow a meaning tied specifically to divine promise and reconciliation.

In the modern era, the rainbow has taken on powerful cultural significance as a symbol of diversity, inclusion, and LGBTQ+ pride, originating with artist Gilbert Baker’s design of the rainbow flag in 1978. The flag’s adoption spread globally, and the rainbow’s natural associations with beauty, variety, and the coming together of different elements into something unified gave it a meaning that resonated far beyond its origins.

The Best Conditions for Seeing a Rainbow

If you want to maximize your chances of seeing a rainbow, a little situational awareness goes a long way. The ideal conditions are: sunlight behind you, rain or mist in front of you, and a relatively low sun angle. This is why rainbows are most commonly seen in the late afternoon or early morning, when the sun is closer to the horizon. A higher sun angle produces a lower arc, and when the sun is more than 42 degrees above the horizon, a rainbow can’t form at all — the arc would be entirely below the ground.

The period just after a passing rain shower is perfect: the air is still full of droplets, the clouds are breaking up, and a patch of clear sky behind you lets the sunlight through. Keep the sun at your back and look toward the darker part of the sky where the rain was.

Waterfalls and garden hoses can produce rainbows too — any fine mist will do. If you’re near Niagara Falls, Victoria Falls, or similar massive waterfalls, you may see nearly continuous rainbows in the mist regardless of the time of day, as long as there’s sunlight. You can also create your own rainbow on a sunny day by standing with the sun behind you and spraying a fine mist from a garden hose in front of you.

Photographing Rainbows

Rainbows can be surprisingly difficult to capture well in photographs, partly because cameras often expose for the bright sky and underexpose the arc, and partly because the wide angle of a full rainbow arc — up to 84 degrees across — is wider than a standard lens can capture. A wide-angle lens or even a fisheye lens can help with the latter. For exposure, slightly underexposing the image (using exposure compensation) tends to make the rainbow’s colors pop against a darker sky.

Polarizing filters, generally useful for landscape photography, should be used carefully around rainbows — they can actually reduce or eliminate the visibility of the rainbow, since the light forming it is already polarized and the filter may block it. Turn the polarizer until the rainbow is at maximum visibility rather than minimum.

Timing is everything. Rainbows can appear and vanish in minutes as the rain moves through, so having your camera ready before the shower ends can make the difference between getting the shot and watching it disappear.

What Isaac Newton Got Right — and What Came After

Newton’s experiments with prisms in the 1660s were foundational, but our understanding of rainbows has deepened considerably since then. René Descartes had already worked out the geometric optics of how light bounces inside a raindrop in 1637, explaining why rainbows appear at the angles they do. Newton added the crucial piece about color separation.

In the 19th and 20th centuries, the wave theory of light explained the supernumerary bows and fogbows that geometric optics couldn’t fully account for. The full quantum mechanical treatment of light goes even deeper still, describing photon interactions with water molecules in probabilistic terms. And yet, even with all of that knowledge, a rainbow in the afternoon sky after a summer storm produces the same catch of breath it always has.

That might be the most remarkable thing about understanding a rainbow: the science doesn’t replace the wonder. It feeds it. When you know that each color is arriving at your eye from a different set of droplets, that the bow would be a full circle if the ground weren’t in the way, that two people standing side by side are seeing slightly different rainbows — the sky becomes a more intricate and astonishing place, not less.

A Final Thought

The rainbow is a reminder that some of the most beautiful things in the world are things that can’t be touched or held — things that exist only in the interaction between light and water and the particular angle of a human eye. It lasts a few minutes. It belongs to no one. And it appears, reliably, wherever the conditions are right, as if the atmosphere itself is performing a trick it has been quietly perfecting for billions of years.

Next time you see one, pause a little longer than you usually would. Look at the dark band between the primary and secondary arc. Notice the subtle supernumerary bands just inside the main bow. Check whether the sky is brighter inside the arc than outside. The rainbow is giving you more information than it looks like at first glance — and it rewards the people who take the time to look carefully.