Is a rainbow actually a full circle?

The Claim

A rainbow is a full circle, but the ground usually hides part of it.

The Answer

NOAA explains rainbows through sunlight, droplets, and viewing geometry. The arc we usually see is a slice of a circular optical effect.

Why This Is Surprising

It sounds like the kind of claim that races around social feeds without context. The source trail matters because the best version of the wonder is the verified one.

How We Checked It

We looked for an authoritative primary source, checked the wording against at least one credible secondary source when available, and recorded the last review date.