# My rainbow: every observer sees different drops

A rainbow appears when sunlight, water drops, and your eyes line up in a precise geometry. Take one step and different drops send light towards you.

## One step changes the drops

When you move, your eyes take a different position relative to the Sun and the rain. Only drops at the right angle send light towards you.

The arc keeps the same angle but changes its drops. That is why the end of a rainbow has no fixed address. Move, and its geometry moves with you.

Interacțiunea principală mută observatorul printr-un câmp sintetic de picături și evidențiază razele potrivite pentru poziția curentă.

## 42° is an angle, not an address

For the primary arc, light reaches your eyes from a direction about 42° from the point opposite the Sun. A drop matters because of where it sits in that geometry.

The same angle draws a circle around the point opposite the Sun. The ground usually hides the lower half, so we see an arc.

- **The Sun:** behind you. light travels from behind you to the drops ahead
- **The rain:** in front of you. suspended drops, spray, or mist
- **Sun height:** below about 42°. otherwise the circle drops below the horizon

## Higher up, more of the circle becomes visible

The ground usually hides the lower part of the circle. If you rise above some of the drops, you can see a wider arc, sometimes almost complete.

The rainbow does not grow. From where you stand, more of the same geometry becomes visible.

## Look behind you

Sun behind you. Rain ahead. About 42° to the centre of the arc. The rest depends on where you stand.

## Where the explanation comes from

Meteorology and physics sources support the claims about refraction, reflection, angle, and observer position. The drawing puts those facts into a simple model. Its points are synthetic.

The explanation summarizes the geometry described by the sources. It does not claim that each observer sees a completely separate phenomenon, or that raindrops stay still.

- [How Do Rainbows Form?](https://www.weather.gov/fgz/Rainbow) . National Weather Service, NOAA. Refraction, internal reflection, dispersion, and the approximate 42° angle of the primary arc.
- [Why Are Rainbows Curved as Semicircles?](https://van.physics.illinois.edu/ask/listing/2195) . Physics Van, University of Illinois. When the observer moves, light reaches the eye from a different set of drops.
- [Ask the Professor: How do rainbows form?](https://www.unr.edu/nevada-today/news/2024/atp-how-do-rainbows-form) . University of Nevada, Reno. An observer higher above the ground can see more of the rainbow circle.
- [Rainbow](https://www.nasa.gov/learning-resources/nasas-picture-dictionary-r/) . NASA Picture Dictionary. A rainbow appears opposite the Sun and needs raindrops, spray, or mist.
- [How Rainbows Are Made](https://scied.ucar.edu/kids/sky-wonders/rainbows) . UCAR Center for Science Education. White light separates into colors as it passes through water droplets.

Publicat și verificat la 12 august 2026. Editat de Marius Comper.