Halos, Order from Disorder

Last updated on September 16, 2023

Halos: Order from Disorder

When we gaze up at the sky on a clear day, we may be fortunate enough to witness a captivating phenomenon known as halos. These beautiful displays of light are created through a delicate dance between the moon, air molecules, and ice crystals. The seemingly chaotic nature of these elements actually gives rise to intricate geometric arcs that adorn the heavens.

At a molecular level, water vapor molecules within the atmosphere move about in a haphazard manner, colliding with one another as they go. However, as the temperature drops and the air cools, these molecules slow down and begin to stick together, forming ice crystals. Surprisingly, rather than resulting in a jumble of disorder, these crystals arrange themselves in an astonishingly organized lattice of hexagons. This hexagonal structure serves as the foundation for the mesmerizing display of halos.

As sunlight passes through these hexagonal ice crystals, it is refracted and dispersed into an array of colors. This refraction creates a glinting effect, transforming the sky into a canvas of ethereal beauty. The intricate geometry of the crystals allows them to act as prisms, bending and scattering the light in specific ways that give rise to the characteristic arcs of halos.

The journey of these ice crystals does not end there. Drifting downwards through the atmosphere, they encounter countless air molecules along the way. Each impact twists and pulls the crystals, gradually aligning them almost perfectly. This alignment is crucial for the formation of the distinct halo patterns that captivate our eyes.

While the moon and ice crystals play a significant role in creating halos, they are not the sole contributors to these celestial wonders. Ground lights also contribute to the spectacle by casting their glow onto the undersides of plate-shaped crystals. This additional light source adds a touch of enchantment to the already mesmerizing display, enhancing the overall visual impact of the halos.

The intricate dance between order and disorder in the creation of halos serves as a reminder of the wondrous complexities that exist within our natural world. From the seemingly random movements of air molecules to the precise alignment of ice crystals, every element plays a crucial role in shaping these ethereal phenomena.

So, the next time you find yourself gazing at the sky and witnessing the breathtaking beauty of halos, take a moment to appreciate the delicate balance between chaos and order that gives rise to these celestial wonders. It is a testament to the harmonious interplay of nature's forces and a reminder of the awe-inspiring intricacies that surround us every day.

Image Credit: Roger Benoit

Order from Disorder

Seen over Switzerland on 8th January by Roger Benoit.

Moon, the patter of air molecules and ice crystals unite to scribe geometric arcs on the sky.

Water vapour molecules speed and collide randomly. When air cools the molecules slow, stick together to form ice. Not in a jumbled way. In a highly ordered geometric lattice of endless hexagons. Which beget hexagonal crystals. Which refract light, glint.

Disorder again. Crystals drift downwards. Untold millions of impacts with air molecules twist and pull to align them almost perfectly.

Sky scribings from disorder.

Image ©Roger Benoit, shown with permission

Ground lights add to the scene by glinting their light from the undersides of plate shaped crystals.

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Reference Atmospheric Optics

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