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Light pillar

earth science Maturity 7-9 Next article →

Have you ever seen a glowing beam in the sky?

Light Pillars and Diamond Dust in London Ontario Canada
Light Pillars and Diamond Dust in London Ontario Canada

This is called a light pillar or an ice pillar. It looks like a vertical line of light. This light can go above or below a light source. It is an atmospheric optical phenomenon. This is a fancy way to say it is a light trick in the air. It is part of a family of lights called halos. These pillars are a beautiful sight to see in the sky.

How does this light trick work?

Light Pillars Scheme
Light Pillars Scheme

Tiny ice crystals float in the air or in high clouds. These crystals are often flat, six-sided plates. As they fall, they stay mostly horizontal. Each tiny flake acts like a small mirror. These mirrors reflect light from a source below them. Many flakes float at different heights in the sky. This makes the reflection look like a long, tall column.

Different things can act as the light source.

Sun pillar and kitesurfers
Sun pillar and kitesurfers

If the light comes from the sun, it is a sun pillar. This often happens when the sun is near the horizon. The moon can also create these pillars. Even streetlights on the ground can do it. Sometimes, even erupting volcanoes can cause the effect. The light pillar is not a real beam of light. It is an optical illusion created by many reflections.

There are special names for certain types of pillars.

Light Pillars and Diamond Dust in London Ontario Canada
Light Pillars and Diamond Dust in London Ontario Canada

In very cold weather, crystals stay near the ground. This is called diamond dust. The more crystals there are, the brighter the pillar looks. Large and many crystals make the effect more pronounced. The pillars belong to the same group as things like sun dogs. They are all ways that light and ice work together.

Think about seeing a light on a wavy lake.

Sun pillar and kitesurfers
Sun pillar and kitesurfers

Ripples on the water reflect the light in many ways. Some of those reflections point straight at you. This makes a bright line on the water. A light pillar works in a similar way. Only the crystals in a certain plane reflect light to your eyes. This is how a simple light becomes a tall, glowing pillar.

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File:Light Pillars and Diamond Dust in London Ontario Canada.jpg
Light Pillars and Diamond Dust in London...
File:Sun pillar and kitesurfers.jpg
Sun pillar and kitesurfers.jpg
File:Light Pillars Scheme.svg
Light Pillars Scheme.svg
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