Why Rainbows Are Circular
They say there’s a pot of gold at the end of the rainbow, but have you ever wondered why there’s an end at all? Technically…I mean, rainbows aren’t arcs at all, they’re circles. Always have been. Is your mind blown yet?
It’s only our feet, our gravity, and our stubborn Earth-bound gaze that sees rainbows as half-truths, hovering above the horizon like divine parentheses. The thing is though, the rainbow doesn’t end…it continues behind the curtain of the earth, in full radiant symmetry.
Behind that curtain is a whole lot of geometry, light, and the storm’s final whisper.
Refractions in the Sky
Rainbows begin with the simplest of ingredients: sunlight and raindrops. The spring is practically bursting with both of these things, plenty of rain mixed with a dollop of sunshine. Simplicity is deceptive in this case though, because inside every droplet is a miracle of physics.
When sunlight hits a raindrop, a few fancy things happen. Refraction is the big one, and this is the light bends as it enters the water. It bounces off the back of the drop which is essentially reflection. Then it bends once again as it exits the drop, which is refraction all over again. You have to love the full-circle moment that brings about a full circle, no? This double refraction and internal reflection act like a prism, splitting sunlight into its many hues: red, orange, yellow, green, blue, indigo, violet. A secret kaleidoscope, revealed only by rain.
Each ray of color emerges at a slightly different angle. Red bends less while violet bends more, and those angles form a very specific geometry. The magic number in case you were wondering is forty-two. I’m not talking numerology, I’m talking about optics. The geometry of light and water creating something that feels like myth.
If you’ve ever stood in the aftermath of a storm, staring at the ghost of color in the air, you’ve felt that mix of math and magic. Your bones recognize the symmetry before your brain catches up.
The Magic Angle: 42 Degrees
Sorry if I got distracted before I explained the whole 42 thing to you. Essentially, each raindrop sends light to your eyes at a very precise angle: about 42 degrees from the line opposite the sun. I get that that sounds random, but it’s actually math. Always 42° for red light and closer to 40° for violet. Every color in a rainbow is the result of countless drops sending one perfect angle of light toward you…and only you.
Which means the rainbow you see is yours, and only yours.
The person standing next to you is seeing a different rainbow entirely, formed by different droplets at the same angles. You can’t chase it, and you can’t catch it, because a rainbow is an intimate secret between your eyes and the sky. If that doesn’t feel both poetic and haunting, I don’t know what does.
If every drop is sending light at a 42° angle, then imagine drawing a compass…one centered around your own shadow, with the sun behind you. What you’d trace…is a circle. It’d be a perfect ring of light, every point equidistant from the center. What we see from the ground is the upper half of that circle, the part that arcs above the horizon.
But if you’re ever lucky enough to be in the right place…like in a plane, or standing at the edge of a waterfall…you’ll see the whole thing: a full halo, a floating wheel of color. The rainbow is complete and always has been, we’re just too grounded to witness its wholeness. Isn’t that just like so many beautiful things in life though, only visible in full from above?
Astronauts and high-altitude pilots have often reported seeing circular rainbows, also called "glories", while flying above clouds or waterfalls. You may have seen them yourself from a window seat on a stormy flight: a bright circle of color encircling the plane’s shadow on the clouds below. That’s the full rainbow, it was always a ring.
A circle of light, visible only when the Earth doesn’t block the bottom half. We’re so used to looking ahead that we forget how different the view can be from above.
Why Don’t We See the Bottom?
It’s not that the rainbow’s bottom doesn’t exist, it’s just hidden. The ground blocks our line of sight, so unless the sun is very low, or you’re very high, you’ll only catch the top of the bow. Sometimes, when the sun is just peeking over the horizon, you’ll see a flatter rainbow. That’s because the 42° cone of light is cutting across your eye line at a lower angle…less of the circle sits above your vision.
But it’s always a circle, even when all you see is a whisper of it. When life hands you only the outline of something whole, trust that it’s still complete.
Rainbows don’t form just anywhere, they need specific conditions like the sunlight must be low, usually early morning or late afternoon. Raindrops must be falling ahead of you while the sun is behind you, and your eyes must be facing away from the sun.
It’s an ephemeral alignment if you will, a perfect collision of angles and timing. That’s why rainbows feel sacred…like nature’s way of bowing, or of breathing relief after chaos. The moment comes and goes faster than you can truly enjoy it. To me, it feels like the atmosphere’s apology after the violence of weather.
Sometimes, if you’re lucky you see not one, but two rainbows. The outer, fainter one is the result of two internal reflections instead of one. This extra bounce flips the colors, so red is on the inside, and violet on the outside. It’s also spread wider, around 50–53°, and appears more ghostlike. A fainter echo of the original bow. It’s the rainbow’s reflection of its own joy.
A prism dream stretched wider than most can see.
There’s something magical about circles that always pulled me in. They have no beginning and no end and they represent unity, infinity, return. A rainbow, in its purest form, is a cone of light: its apex at your eye, and its circular base expanding outward. The curved bow we see is a cross-section of that cone. You’re standing inside geometry, inside a beam of divided sunlight. We walk through equations without knowing it then drink prisms through our eyes and call it beauty.
Seeing the Shape in a World That Hides It
Much like constellations or auroras, rainbows live in that space between science and story. We know their physics and can model their math, but they still feel…alive.
It could be because they’re untouchable or they appear when the sky is healing. Maybe it’s because they’re perfect geometry, circles seen through tears.
They don’t need to last. Even after chaos, clarity arcs through, and in disorder, color aligns. Even if you can’t see the whole thing, it’s still complete.
The pot of gold isn’t at the end, it’s inside the light itself.
Rainbow Glass Prism for Light Experiments
Let sunlight play. Use this real glass triangular prism to make your own indoor rainbows, great for photographers, kids, or curious minds.
Handmade Rainbow Suncatcher
A stained glass hanging piece that throws circular rainbows across your walls with the morning sun.
