Everything Everywhere Daily: History, Science, Geography & More Rainbows And How They Work
May 10, 2026
Sunlight, water droplets, and geometry combine to paint colorful arcs in the sky. Learn why rainbows form circular shapes and why primary and secondary bows show different colors and brightness. Explore related atmospheric displays like halos, sundogs, and glories. Hear how rainbows inspired myths and how scientists from Aristotle to Newton probed their optical secrets.
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How A Rainbow Is Physically Created
- Rainbows form when sunlight refracts, disperses, internally reflects, and refracts again inside many tiny water droplets.
- Red emerges ~42° from the anti-solar point and violet ~40°, so millions of droplets at those angles produce the colored circular arc you see.
Rainbows Are Circular Cones Not Arches
- A rainbow is actually a circular cross-section of a cone of light centered on the anti-solar point, not a simple arch.
- From ground level the horizon blocks the bottom; from airplanes or mountains you can sometimes see a full circle.
Why Double Rainbows Reverse Colors
- Double rainbows occur when light reflects twice inside a raindrop, exiting at a larger angle around 51–54°.
- The second reflection makes the secondary bow dimmer, wider, and reverses the color order: red inside, violet outside.