On the coldest, stillest winter nights, columns of coloured light can appear to rise from a town straight into the sky. These are light pillars: reflections of streetlights, floodlights and car parks in countless tiny ice crystals floating in the air. The photographs below follow them from the Finnish ski resort of Ruka to snowbound towns in Colorado, Idaho, Wyoming and Alaska.
How light pillars form
A light pillar is an optical effect in which a vertical beam seems to extend above or below a light source. It is created by flat, hexagonal plate-shaped ice crystals. As they drift down, these plates tend to settle almost horizontally, so each one behaves like a tiny mirror.
Millions of these mirrors at different heights send the light of a lamp back towards the observer, and together they stretch its reflection into a tall column. The effect works the same way as the long, shimmering streak a street lamp throws across rippled water. The pillar is not a physical beam standing over the lamp; it exists only along the line between the light, the crystals and your eyes.
Meteorologists group light pillars with the halo family of phenomena, because all of them come from light interacting with ice crystals. When the light source is the low Sun, the result is called a sun pillar. The Moon, and even erupting volcanoes such as Etna, can produce pillars too.
The weather that makes them
Light pillars need very cold air close to the ground, where ice crystals hang suspended like a fine glitter known as diamond dust. Jeroen Stil, a physicist at the University of Calgary, told CBC News that these crystals form at temperatures below about −20 °C, although Roland Dechesne of the Royal Astronomical Society of Canada has seen pillars at around −11 °C.
The air also has to be calm. Wind tumbles the plates out of their horizontal position and the mirror effect collapses. That is why the best displays come on clear, frigid, windless nights in places such as Lapland, the Canadian Prairies, Alaska and the high valleys of the Rocky Mountains.
Why town lights make tall, coloured columns
Pillars from streetlights often look taller than sun pillars. Optical-phenomena expert Les Cowley of Atmospheric Optics explains that light from a nearby lamp is not parallel, so plates with only slight tilts can still reflect it downwards to the observer. The crystals doing the work sit roughly halfway between you and the lamp, so when they surround you, pillars can appear above lights just a few metres away.
Very high crystals or very close lights can make the pillars appear to converge overhead, like the spokes of a wheel. The colours simply come from the lamps themselves: sodium lights give orange pillars, while white LEDs, coloured signs and stadium floodlights add their own shades. A single town can produce a whole row of different columns.
Where the photos were taken
- Ruka, Finland: a fell and ski resort in Kuusamo, 492 metres high, with 41 slopes and 21 lifts. Its season usually runs from October to June, one of the longest in Europe.
- Granby, Colorado: a small town in Grand County, high in the Rockies.
- Moscow, Idaho: the university town in the Palouse region of northern Idaho, not the Russian capital.
- Laramie, Wyoming: a high-plains city known for long, very cold winters.
- Anchorage, Alaska: Alaska’s largest city, where winter nights are long and dark.
How to see and photograph light pillars
Watch the forecast for clear skies, light winds and deep cold, then head to the edge of town where you can look back at unshielded lights. Pillars can come and go within minutes as the crystals drift, so be patient and try several angles.
For photographs, use a tripod and a long exposure, and frame the pillars with buildings or trees below them so the scale reads clearly. Dress for the conditions: nights cold enough for pillars are cold enough to numb fingers and drain camera batteries fast, so carry spares in an inside pocket.
Pillars are often confused with the northern lights, but auroras glow high in the upper atmosphere and move in curtains and arcs, while light pillars stay locked above their light sources. For more sky optics, see the sun halos produced by ice crystals and aurora light in an Icelandic film.
Related reading
- Kakslauttanen’s Glass Igloos: A Room with a Sky View
- Snowboarding and Freestyle in Finnish Lapland
- Ten Northern-Lights Regions: Geography, Darkness and Realistic Expectations
- Finnish Lapland in Winter: Forests, Light and Snow-Covered Landscapes
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